Outer and inner coordination sphere chemistry of polyazacyclophane platinum(II) complexes. Crystal structure of [PtBr4]2(H4L1) · H2O (L1 = 2,6,9,13-tetraaza[14]paracyclophane)

Abstract The interaction of PtCl42− with the new azaparacyclophane 2,5,8,11-tetraaza[12]paracyclophane (L2) has been studied by 1H, 13C and 195Pt NMR spectroscopy. Three different complexes are detected as a function of pH, all of them presenting cis-arrangement of nitrogen donors and chloride anions. In the first one, formed at acidic pH, the central nitrogen atoms of the macrocyclic are coordinating to Pt(II) while the benzylic nitrogens remain protonated. Deprotonation of these nitrogens brings about a reorganisation of the complex, and the platinum is then coordinated by one benzylic nitrogen and the consecutive nitrogen in the macrocycle. This process can be monitored by NMR. Finally, …

Preparation of Polymer-Supported Polyazamacrocycles. The Role of the Polymeric Matrix in the Preparation of Polymer-Supported Polyazamacrocycles

Different approaches have been studied for the preparation of resins containing different polyazamacrocycles. Preparation of monolithic resins by polymerization of vinylic derivatives of the corresponding macrocycles is shown to be a more versatile strategy for this purpose. The use of energy-dispersive analysis by X-ray has revealed to be a very useful tool for the rapid evaluation of the interaction of those materials with both anions and cations and has allowed the corresponding selectivity trends to be obtained in a fast and simple way. Important effects of the polymeric matrix are observed in some cases.

Electrochemically-driven conformational shift in mono- and di-copper constrained macrotricyclic cyclen receptors

International audience; An electrochemical study of mono- and di-copper constrained cyclen macrotricycles is presented. Electrochemical data in DMF solution indicate that the reduction of dinuclear complexes occurs in two steps in the -0.4 to -0.8 V vs.AgCl/Ag potential range yielding CuII CuI and CuI CuI species further reduced to Cu metal at highly negative potentials. Mononuclear complexes are reduced in two steps to CuI and Cu metal. Electrochemical data suggest that reduction of both mononuclear and dinuclear complexes approach a square scheme involving electrochemically-driven conformational shifts for metal ions. The presence of endo- and exo-forms of the complexes are revealed by ch…

Modulation of DNA binding by reversible metal-controlled molecular reorganizations of scorpiand-like ligands.

DNA interaction with scorpiand azamacrocycles has been achieved through modulation of their binding affinities. Studies performed with different experimental techniques provided evidence that pH or metal-driven molecular reorganizations of these ligands regulate their ability to interact with calf thymus DNA (ctDNA) through an intercalative mode. Interestingly enough, metal-driven molecular reorganizations serve to increase or decrease the biological activities of these compounds significantly.

Homo- and heterobinuclear Cu2+ and Zn2+ complexes of abiotic cyclic hexaazapyridinocyclophanes as SOD mimics

The new receptor 3,7,11,15,19,23-hexaaza-1(2,6)-pyridinacyclotetracosaphane (L1) containing a complete sequence of propylenic chains has been synthesised. The acid–base behaviour and Cu2+ and Zn2+ coordination have been analysed by potentiometric measurements in 0.15 M NaClO4 for L1 and for the related compounds 3,7,11,14,18,22-hexaaza-1(2,6)-pyridinacyclotricosaphane (L2), 3,7,10,13,16,20-hexaaza-1(2,6)-pyridinacycloheneicosaphane (L3) and 3,7,10,12,15,19-hexaaza-1(2,6)-pyridinacycloicosaphane (L4). The crystal structure of [(CuH4L2)(H2O)(ClO4)](ClO4)5·3H2O shows an interesting combination of a metal ion coordinated by the pyridine nitrogen atom and the adjacent amine groups of the chain, …

Metal Complexes as Receptors

The role played by metal complexes as receptors of different substrates is discussed. For this purpose, several relevant examples of the work performed by different research groups have been briefly discussed. The metal complexes have been organized attending to the molecular topology of the ligands employed. The article ends with the description of metallocages in which at least one of the metal ions constituting the cage framework binds the guest through coordinative bonds.

Significant in vivo anti-inflammatory activity of Pytren4Q-Mn a superoxide dismutase 2 (SOD2) mimetic scorpiand-like Mn (II) complex.

Background The clinical use of purified SOD enzymes has strong limitations due to their large molecular size, high production cost and immunogenicity. These limitations could be compensated by using instead synthetic SOD mimetic compounds of low molecular weight. Background/Methodology We have recently reported that two SOD mimetic compounds, the MnII complexes of the polyamines Pytren2Q and Pytren4Q, displayed high antioxidant activity in bacteria and yeast. Since frequently molecules with antioxidant properties or free-radical scavengers also have anti-inflammatory properties we have assessed the anti-inflammatory potential of Pytren2Q and Pytren4Q MnII complexes, in cultured macrophages …

Studies on the interaction of phosphate anions with N-functionalised polyaza[n]paracyclophanes: the role of N-methylation.

The synthesis and interaction of N,N',N'',N'''-tetramethyl-2,6,9,13-tetraaza[14]paracyclophanes (B323Me(4)) with nucleotides and inorganic phosphates is described. An easy methodology is used to define thermodynamic selectivity. The interaction of B323Me4 and ATP has been monitored by (1)H, (31)P NMR and by molecular mechanics, ruling out the possibility of the participation of pi-stacking interactions. Results show that N-methylation is accompanied by a strong increase in the interaction of the resulting macrocycle with ATP.

Ditopic Aza-Scorpiand Ligands Interact Selectively with ds-RNA and Modulate the Interaction upon Formation of Zn2+ Complexes

Nucleic acids are essential biomolecules in living systems and represent one of the main targets of chemists, biophysics, biologists, and nanotechnologists. New small molecules are continuously developed to target the duplex (ds) structure of DNA and, most recently, RNA to be used as therapeutics and/or biological tools. Stimuli-triggered systems can promote and hamper the interaction to biomolecules through external stimuli such as light and metal coordination. In this work, we report on the interaction with ds-DNA and ds-RNA of two aza-macrocycles able to coordinate Zn2+ metal ions and form binuclear complexes. The interaction of the aza-macrocycles and the Zn2+ metal complexes with duple…

Polyamine Linear Chains Bearing Two Identical Terminal Aromatic Units. Evidence for a Photo Induced Bending Movement

Abstract Several chemosensors bearing a fluorescent unit at both ends of a linear polyamine chain were synthesised. The protonation as well as the association constants with Cu2+ and Zn2+ were determined by potentiometry in 0.15 mol dm−3 NaCl at 298.1 K. In the case of 1,16-bis(1-naphthylmethyl)-1,4,7,10,13,16-hexaazadecane hexahydrochloride (L1), formation of an excimer emission in aqueous acidic solutions was observed. The system was characterized by steady state fluorescence emission and by time resolved fluorescence. In the ground state the molecule is expected to adopt a more or less linear conformation, while in the excited state a bending movement of the chain must occur in order to …

One-pot preparation of surface modified boehmite nanoparticles with rare-earth cyclen complexes.

We report on the one-pot synthetic procedure of cyclen derivatives bearing three acetate groups attached on boehmite nanoparticles, the complexing capabilities of these inorganic–organic hybrid materials with rare earth cations, and the behaviour as contrast agents or fluorescence probes. Delgado Pinar, Estefania, Estefania.Delgado@uv.es ; Frias Martinez, Juan Carlos, Juan.Frias@uv.es ; Albelda Gimeno, Maria Teresa, Teresa.Albelda@uv.es ; Alarcon Navarro, Javier, Javier.Alarcon@uv.es ; Garcia-España Monsonis, Enrique, Enrique.Garcia-Es@uv.es

Thermodynamics of sulfate anion binding by macrocyclic polyammonium receptors

The interaction of SO42− with polyammonium cations derived from fourteen polyamines (5 polyazacycloalkanes, 2 polyazacyclophanes, 3 phenanthrolinacyclophanes, 2 dibenzenacyclophanes and 2 acyclic polyamines) in aqueous solution has been studied by means of potentiometric and microcalorimetric techniques. Only 1 : 1 receptor–anion complexes have been found in solution. Complexed species of considerable stability are formed, although the two acyclic polyamines (dimethylpentaethylenehexaamine and dimethylhexaethyleneheptaamine) and the smallest phenanthrolinacyclophane do not interact with the anion. The complexation reactions are endothermic, or almost athermic, and promoted by invariably fav…

The size of aryl linker between two polyaza-cyclophane moieties controls the binding selectivity to ds-RNA vs ds-DNA

Aryl-linked (pyridine- vs. phenanthroline-) bis-polyaza pyridinophane scorpiands PYPOD and PHENPOD strongly bind to the double stranded DNA and RNA, whereby very intriguing RNA over DNA selectivity is finely tuned by aryl-linker length and aromatic surface. Moreover, PYPOD and PHENPOD dimer formation at high compound/polynucleotide ratios is highly sensitive to the fine interplay between the steric and binding properties of compound-dimers and the DNA minor groove/RNA major groove. That is demonstrated by significantly different induced CD spectra, which allow spectroscopic differentiation between various DNA/RNA secondary structures. A significantly higher (micromolar) antiproliferative ef…

Visualizing the atherosclerotic plaque: a chemical perspective.

Atherosclerosis is the major underlying pathologic cause of coronary artery disease. An early detection of the disease can prevent clinical sequellae such as angina, myocardial infarction, and stroke. The different imaging techniques employed to visualize the atherosclerotic plaque provide information of diagnostic and prognostic value. Furthermore, the use of contrast agents helps to improve signal-to-noise ratio providing better images. For nuclear imaging techniques and optical imaging these agents are absolutely necessary. We report on the different contrast agents that have been used, are used or may be used in future in animals, humans, or excised tissues for the distinct imaging moda…

ChemInform Abstract: Fluorescent Chemosensors Containing Polyamine Receptors

Chemosensors have attracted interest in many different scientific fields, such as environmental chemistry, medicine, and the processing and storage of information. These molecular-scale devices have the advantage of working on the same spatial scale as the chemical structures that are responsible for macroscopic behaviour observed in the environment or those associated with health problems. Moreover, they allow the construction of molecular-scale devices for information storage. In this review, we describe a family of chemosensors based on a polyamine receptor and a fluorescent signalling unit. Polyamine receptors are water-soluble ambidentate receptors; they are able to coordinate either m…

Preparation of Hg2+ selective fluorescent chemosensors based on surface modified core–shell aluminosilicate nanoparticles

A synthetic procedure for the preparation of functional structured inorganic–organic hybrid materials consisting of boehmite-silica core–shell nanoparticles and anthracene-containing amines covalently attached to the nanoparticles surface is reported. The system functionalised with the monoamine chain shows a very high sensing performance for Hg2+ detection in pure water reaching a detection limit of 0.2 ppb. Two additional advantages of these systems are their stability over a wide pH window and the feasibility to be recovered by a simple procedure.

Compounds of molybdenum(VI) with aspartic acid: A spectrophotometric and potentiometric study of the formation and interconversion equilibria in aqueous solution

Addition of Na2MoO4 to an excess of aspartic acid (AspH2) can produce any of four different complexes depending on the pH, namely [MoO3(Asp)]2−, [Mo2O5(Asp)2]2−, [Mo2O4(OH)(Asp)2]− and [Mo2O4(Asp)2]. The ranges of formation of these species with pH, the number of equivalents of acid necessary for their formation, and their stoichiometries, condensation degrees and stability constants, have been calculated by potentiometric and spectrophotometric techniques. The aspartic acid acts as a tridentate ligand in all cases.

Triazolopyridines. Part 28. The ring–chain isomerization strategy: triazolopyridine- and triazoloquinoline–pyridine based fluorescence ligands

Abstract The ring–chain isomerization of [1,2,3]triazolo[1,5-a]pyridines or [1,2,3]triazolo[1,5-a] quinolines has been efficiently employed as a tool to provide tridentate fluorescent structures. Based on these scaffolds, a new family of highly fluorescent compounds has been synthesized and evaluated for the recognition of zinc or copper cations. In addition, the 1:1 Zn+2-L complex of a naphthalene triazolopyridine–pyridine derivative revealed high efficiency as sensor for anions providing large binding constants for nitrite and cyanide.

In vitro activity of scorpiand-like azamacrocycle derivatives in promastigotes and intracellular amastigotes of Leishmania infantum and Leishmania braziliensis.

The activity of a family scorpiand-like azamacrocycles against Leishmania infantum and Leishmania braziliensis was studied using promastigotes, axenic and intracellular amastigotes forms. All the compounds are more active and less toxic than meglumine antimoniate (Glucantime). Moreover, the data on infection rates and amastigotes showed that compounds P2Py, PN and P3Py are the most active against both species of Leishmania. On the other hand, studies on the inhibitory effect of these compounds on SOD enzymes showed that while the inhibition of the Fe-SOD enzyme of the promastigote forms of the parasites is remarkable, the inhibition of human CuZn-SOD and Mn-SOD from Escherichia coli is negl…

Synthesis and Structural Characterization of a Cyclen-Derived Molecular Cage

Reaction of a tetrafunctionalized cyclen derivative containing four aldehyde groups with an appropriate diamine followed by reduction and demetalation highly efficiently affords a bis(cyclen)-derived molecular cage. Potentiometric investigations show that this compound forms dimetallic complexes with copper(II), with the two metal ions selectively coordinated to the cyclen units. X-ray crystallography indicates that these complexes could give rise to new cascade complexes after incorporation of anions between the metal centers.

A Binuclear MnIII Complex of a Scorpiand-Like Ligand Displaying a Single Unsupported MnIII–O–MnIII Bridge

The crystal structure of a binuclear Mn(III) complex of a scorpiand-like ligand (L) displays an unsupported single oxo bridging ligand with a Mn(III)-O-Mn(III) angle of 174.7°. Magnetic susceptibility measurements indicate strong antiferromagnetic coupling between the two metal centers. DFT calculations have been carried out to understand the magnetic behavior and to analyze the nature of the observed Jahn-Teller distortion. Paramagnetic (1)H NMR has been applied to rationalize the formation and magnetic features of the complexes formed in solution.

Trapping a Highly Reactive Nonheme Iron Intermediate That Oxygenates Strong C—H Bonds with Stereoretention

An unprecedentedly reactive iron species (2) has been generated by reaction of excess peracetic acid with a mononuclear iron complex [FeII(CF3SO3)2(PyNMe3)] (1) at cryogenic temperatures, and characterized spectroscopically. Compound 2 is kinetically competent for breaking strong C-H bonds of alkanes (BDE ≈ 100 kcal·mol-1) through a hydrogen-atom transfer mechanism, and the transformations proceed with stereoretention and regioselectively, responding to bond strength, as well as to steric and polar effects. Bimolecular reaction rates are at least an order of magnitude faster than those of the most reactive synthetic high-valent nonheme oxoiron species described to date. EPR studies in tande…

Dinuclear Zn II Complexes of Polydentate Polyamines as Minimalist Models of Hydrolytic Reactions

The synthesis of the novel macrocycle 2,6,9,12,16-pentaaza[17](2,9)(1,10)phenanthrolinophane (L3) is reported. Speciation studies on the systems ZnII−L3 and ZnII−L2 (L2 =2,6,10,13,17,21-hexaaza[22]metacyclophane) performed in aqueous solution show the formation of mono- and dinuclear ZnII complexes. In the two systems, the dinuclear complexes readily hydroxylate, with the hydroxo species being the main ones in solution at relatively low pH values. This feature makes these complexes promising hydrolytic agents for carboxy and phosphate esters. The hydrolytic ability of the L1−L3 dinuclear complexes toward the carboxy and phosphate ester bond was tested by addition of p-nitrophenyl acetate (N…

Dramatic selectivity differences in the association of DNA and RNA models with new ethylene- and propylene diamine derivatives and their copper complexes.

The affinities of polyamines consisting of ethylenediamine units equipped with either one or two terminal naphthyl-, anthryl-, or acridyl units towards PolyA.PolyU as an RNA model, and Poly(dA).Poly(dT) as a DNA model are screened by measuring the melting point changes (DeltaT(m)) of the double strands, and also partially by a fluorimetric binding assay using ethidium bromide. The larger aromatic moieties with long spacers between them allow bisintercalation; this leads to an increased preference for DNA in comparison to RNA, where ion pairing of the ammonium centers with the major RNA groove phosphates dominates. Allosteric affinity control by metalation is achieved e.g. with Cu(2+) ions, …

A step forward in the development of superoxide dismutase mimetic nanozymes: the effect of the charge of the surface on antioxidant activity

Two binucleating hezaaza macrocycles containing a pyridinol spacer have been prepared and characterised. Protonation studies indicate the deprotonation of the phenol group at relatively low pH values with the concomitant occurrence of a keto-enolic equilibrium. These ligands readily form binuclear Cu2+ and Zn2+ complexes as denoted by potentiometric and spectroscopic studies. The binding of the metals yields to the ready deprotonation of the phenol with the stabilisation of the keto form that results in complexes of greater stabilities than the analogous ones containing pyridine as spacer instead of pyridine. Mixed Cu2+–Zn2+-complexes were also detected in aqueous solutions containing equim…

Equilibrium and kinetic studies on complex formation and decomposition and the movement of Cu2+metal ions within polytopic receptors

Potentiometric studies carried out on the interaction of two tritopic double-scorpiand receptors in which two equivalent 5-(2-aminoethyl)-2,5,8-triaza[9]-(2,6)-pyridinophane moieties are linked with 2,9-dimethylphenanthroline (L1) and 2,6-dimethylpyridine (L2) establish the formation of mono-, bi- and trinuclear Cu(2+) complexes. The values of the stability constants and paramagnetic (1)H NMR studies permit one to infer the most likely coordination modes of the various complexes formed. Kinetic studies on complex formation and decomposition have also been carried out. Complex formation occurs with polyphasic kinetics for both receptors, although a significant difference is found between bot…

Potential ATPase mimics by polyammonium macrocycles: Criteria for catalytic activity

Abstract A series of polyammonium macrocycles, ranging in size from the 18-membered ring [18]aneN6 to the 36-membered [36]aneN12 were examined as potential ATPase mimics. The rates of hydrolysis of ATP were followed at pH 3.0 and 7.0 using 31P NMR and HPLC techniques. Stability constants as a function of degree of protonation, distribution curves for the ligands as a function of pH, and distribution curves for the mixed species of nucleotides, inorganic phosphate, and macrocycle were also determined. All of the macrocycles catalyzed the hydrolysis of ATP to some extent compared to noncatalyzed hydrolysis. A critical dependence on macrocyclic ring size was observed, with [21]aneN7 being the …

Open-chain polyamine ligands bearing an anthracene unit - Chemosensors for logic operations at the molecular level

In this work the absorption and the fluorescence emission properties as well as the protonation sequence of three open chain polyamine ligands of different dimensions bearing an anthracene unit were studied. The protonation and stability constants with Ni2+, Cu2+, Zn2+, and Cd2+ have been determined in 0.15 mol·dm−3 NaCl at 298.1 ± 0.1 K. The values of both protonation and stability constants follow the expected trends according to the number of nitrogen donors, sequence of chelate rings and hydrophilic−hydrophobic balance. Chelation enhancement of the fluorescence emission (CHEF) was observed for some complexes of these ligands with Zn2+ and Cd2+. In contrast the analog complexes containin…

A simple helical macrocyclic polyazapyridinophane as a stereoselective receptor of biologically important dicarboxylates under physiological conditions.

The interaction of a synthetic enantiopure azamacrocyclic receptor (L) with biologically important chiral dicarboxylates (A, 1-7) has been studied by means of potentiometric titrations in 0.15 M NaCl aqueous solution in a wide pH range. This macrocycle forms strong complexes of the type [HnLA](n-2) (with n = 0-5). As a general trend, the binding is much tighter at basic or neutral pH than in acidic medium. Interestingly, nonprotected excitatory amino acids (Asp and Glu) are strongly bound even at acidic pH. Regarding selectivity, the receptor showed stereoselective binding toward those substrates bearing an H-bonding donor at Calpha, being S-selective in most of the cases, except for glutam…

Synthesis, Optical Properties, and DNA Interaction of New Diquats Based on Triazolopyridines and Triazoloquinolines

New diquat derivatives based on [1,2,3]triazolo[1,5-a]pyridine and [1,2,3]triazolo[1,5-a]quinoline have been synthesized in excellent yields. To evaluate the effect of the alkyl bridge length, ethane and propane dibromo alkane substrates were used for their synthesis. Theoretical calculations predicted a very small energetic barrier between the two possible enantiomers P (Ra ) and M (Sa ), which makes them very difficult to resolve. Thermal denaturation studies, UV/Visible spectroscopy, and fluorescence titrations with ct-DNA evidenced the intercalation of the quinoline derivatives in DNA.

Unusual phosphine oxidation: new triazolopyridyl-quinolyl phosphine oxide fluorescent dyes

3-(2-Pyridyl)-[1,2,3]triazolo[1,5-a]quinolylphosphines suffer an unusual phosphine oxidation due to their special geometry that allows a s-donation of the nitrogen (N1) lone pair to phosphorus. This family of compounds behaves as strong fluorophores with high quantum yields.

Guanosine-5'-Monophosphate Polyamine Hybrid Hydrogels: Enhanced Gel Strength Probed by z-Spectroscopy.

The self-assembling tendencies of guanosine-5'-monophosphate (GMP) can be drastically increased using polyamines, with potential applications in the production of biocompatible smart materials, as well as for the design of anti-tumoral drugs based on G-quadruplex stabilization. Results from scanning electron microscopy (SEM), wide angle X-ray scattering (WAXS), rheology and nuclear magnetic resonance (NMR) z-spectroscopy studies are presented.

Equilibrium and kinetics studies on bibrachial lariat aza-crown/Cu(II) systems reveal different behavior associated with small changes in the structure

Abstract The high-yield synthesis of a new bibrachial lariat azacrown constituted by two tris(2-aminoethyl)amine (tren) units functionalized in one of its arms with a 4-methylquinoline group linked by dimethylene pyridine spacers (L2) is reported for the first time. The speciation studies show formation of mono- and binuclear Cu2+ complexes of similar stability. Comparisons are established with the complexes formed by the precursor tren-quinoline derivative (L4) and with the previously reported ligands containing naphthalene instead of quinoline as the fluorophore (L1, L3). The kinetics of formation and decomposition of Cu2+ complexes with L1 and L2 has been studied. For L1, the acid-promot…

Binuclear Cu2+ complex mediated discrimination between L-glutamate and L-aspartate in water.

L-Glutamate and L-aspartate selectivity is achieved by the action of two Cu2+ metal ions rightly disposed in a cyclophanetype macrocyclic framework; electrochemical sensing of glutamate has been achieved by adsorption of the copper complexes on graphite electrodes. Verdejo Viu, Begoña, Begona.Verdejo@uv.es ; Domenech Carbo, Antonio, Antonio.Domenech@uv.es ; Jimenez Garcia, Hermas Rafael, Hermas.Jimenez@uv.es ; Soriano Soto, Concepción, Concepcion.Soriano@uv.es ; Garcia-España Monsonis, Enrique, Enrique.Garcia-Es@uv.es

Proton coordination by polyamine compounds in aqueous solution

Abstract The present article is concerned with proton transfer reactions in aqueous solution of open-chain, macrocyclic and macropolycyclic or cage compounds having nitrogen atoms as protonation sites in the molecular framework, although several compounds with additional different donors will be considered. The main purpose of this review is to collect some significant examples of proton transfer processes in order to show how the electronic properties and molecular topology of polyamines affect the thermodynamic parameters of their protonation equilibria.

Copper(II) complexes of quinoline polyazamacrocyclic scorpiand-type ligands: X-ray, equilibrium and kinetic studies

The formation of Cu(II) complexes with two isomeric quinoline-containing scorpiand-type ligands has been studied. The ligands have a tetraazapyridinophane core appended with an ethylamino tail including 2-quinoline (L1) or 4-quinoline (L2) functionalities. Potentiometric studies indicate the formation of stable CuL(2+) species with both ligands, the L1 complex being 3-4 log units more stable than the L2 complex. The crystal structure of [Cu(L1)](ClO(4))(2)·H(2)O shows that the coordination geometry around the Cu(2+) ions is distorted octahedral with significant axial elongation; the four Cu-N distances in the equatorial plane vary from 1.976 to 2.183 Å, while the axial distances are of 2.27…

Water-Soluble Squaramide Dihydrates: N-Methylation Modulates the Occurrence of One- and Two-Dimensional Water Clusters through Hydrogen Bonding and Dipolar Interactions

Water confined in molecular size domains is distinct to bulk water. The altered interactions between adjacent water molecules, and between water molecules and molecular wall components of the confinement system, determine aspects of important phenomena in material science, biology, and nanotechnology. The structural determination of confined water, however, has proven to be challenging. Here, we describe the crystal structures of three related squaramides 1–3 whose molecular structures are modulated by the gradual incorporation of N-methyl groups to the squaramide moiety. The three squaramides differ in their hydrogen bonding capabilities due to the different degree of N-methylation of each…

New polyamine drugs as more effective antichagas agents than benznidazole in both the acute and chronic phases.

Abstract Despite the continuous research effort that has been made in recent years to find ways to treat the potentially life threatening Chagas disease (CD), this remains the third most important infectious disease in Latin America. CD is an important public health problem affecting 6–7 million people. Since the need to search for new drugs for the treatment of DC persists, in this article we present a panel of new polyamines based on the tripodal structure of tris(2-aminomethyl)amine (tren) that can be prepared at low cost with high yields. Moreover, these polyamines present the characteristic of being water-soluble and resistant to the acidic pH values of stomach, which would allow their…

Correlation between the molecular structure and the kinetics of decomposition of azamacrocyclic copper(II) complexes

The formation of copper(II) complexes with symmetrical dinucleating macrocyclic ligands containing two either monomethylated (L1) or trimethylated (L2) diethylenetriamine (Medien or Me3dien) subunits linked by pyridine spacers has been studied by potentiometry. Potentiometric studies show that L1 has larger basicity than L2 as well as higher stability of its mono- and binuclear complexes. The crystal structures of L1·6HCl (1), [Cu2(L1)Cl2](CF3SO3)2 (2), [Cu2(L1)(OH)](ClO4)3·3H2O (3) and [Cu(L1)](ClO4)2 (4) show that L1 adopts different coordination modes when bound to copper(II). Whereas in 2, each copper(II) is bound to one Medien subunit and to one pyridine group, in 3 each metal center i…

The structure of ammonium pyrazolates in the solid state

The crystals obtained by mixing equimolar amounts of diethyl 1H-pyrazole-3,5-dicarboxylate and the primary amines phenethylamine and homoveratrylamine are ammonium pyrazolate salts as determined by 13C and 15N CPMAS NMR. Copyright © 2006 John Wiley & Sons, Ltd.

Synthetic single and double aza-scorpiand macrocycles acting as inhibitors of the antioxidant enzymes iron superoxide dismutase and trypanothione reductase in Trypanosoma cruzi with promising results in a murine model

The anti-chagasic activity of a series of eleven derivatives of aza-scorpiand-like macrocycles, some of them newly synthesised, was assayed. The four compounds with the best selectivity indices in vitro were subjected to in vivo assays. Tests in a murine model of the acute phase of Chagas disease showed a two-fold reduction in parasitaemia compared to that with benznidazole. Furthermore, compounds 7 and 11, with 4-pyridine and phenanthroline substituents in the lateral chain, caused a remarkable decrease in parasitaemia reactivation during the chronic phase after inducing immunosuppression in mice. These activity studies were complemented by measuring their inhibitory effect towards the ant…

Bisferrocenyl-functionalized pseudopeptides: access to separated ionic and electronic contributions for electrochemical anion sensing

Pseudopeptidic receptors containing ferrocene fragments have been prepared and their response to a series of anions was measured by a voltammetry of microparticles methodology. Such water-insoluble compounds yield anion-assisted reversible solid-state oxidations differing in their open-circuit potential and their midpeak potential recorded in cyclic voltammetric measurements. The difference between those potentials provides the individual thermodynamic contributions of electron and proton transfer, revealing that the mechanism of an ion-sensitive electrode can differ in potentiometry and voltammetry. The studied receptors are potentially interesting for potentiometric sensing, showing relat…

Switching from intramolecular energy transfer to intramolecular electron transfer by the action of pH and Zn2+ co-ordination

Abstract Intramolecular electron (eT) and energy transfer (ET) have shown to occur in a covalently linked donor–acceptor (CLDA) system consisting of a naphthalene donor covalently linked through a polyamine chain connector to an anthracene acceptor; the connector has been chosen in order to switch ON or OFF the energy flux as a function of its protonation state as well as by co-ordination to Zn 2+ . The largest energy transfer efficiency ( η =0.61) occurs for the fully protonated form (pH 9 (eT) from the lone pairs of the nitrogens to the excited fluorophore takes place, leading to complete quenching of the emission. On the other hand at neutral and basic pH values, co-ordination of Zn 2+ p…

Polyfunctional Tetraaza-Macrocyclic Ligands: Zn(II), Cu(II) Binding and Formation of Hybrid Materials with Multiwalled Carbon Nanotubes

The binding properties of HL1, HL2, and HL3 ligands toward Cu(II) and Zn(II) ions, constituted by tetraaza-macrocyclic rings decorated with pyrimidine pendants, were investigated by means of potentiometric and UV spectrophotometric measurements in aqueous solution, with the objective of using the related HL-M(II) (HL = HL1–HL3; M = Cu, Zn) complexes for the preparation of hybrid MWCNT-HL-M(II) materials based on multiwalled carbon nanotubes (MWCNTs), through an environmentally friendly noncovalent procedure. As shown by the crystal structure of [Cu(HL1)](ClO4)2, metal coordination takes place in the macrocyclic ring, whereas the pyrimidine residue remains available for attachment onto the s…

CO 2 Fixation and Activation by Cu II Complexes of 5,5″‐Terpyridinophane Macrocycles

An aza-terpyridinophane receptor containing the polyamine 4,7,10,13-tetraazahexadecane-1,16-diamine linked through methylene groups to the 5,5″ positions of a terpyridine unit has been prepared and characterized (L). The acid-base behaviour, CuII speciation and ability to form ternary complexes (CuII-L-carbonate) have been explored by potentiometric titrations in 0.15 M NaClO4 and by UV/Vis and paramagnetic NMR spectroscopy. Comparisons are made with a previously reported terpyridinophane containing the polyamine 4,7,10-triazatridecane-1,13-diamine (L1). For this latter receptor, reductive coupling between indigo and carbon dioxide at indigo-modified electrodes produces carboxylated derivat…

Naphthalene-containing polyamines supported in nanosized boehmite particles

Boehmite nanoparticles with covalently linked polyamine chains functionalized with naphthalene fluorophores have been prepared and characterized. The characterization of the materials by elemental microanalysis, X-ray powder diffraction, MAS 29Si NMR and electron microscopy unambiguously prove that the covalent anchorage had occurred. Steady-state fluorescence emission studies show that the luminescent properties of the modified nanoparticles are sensitive to changes in concentration of hydrogen ions, metal ions and anionic nucleotides such as ATP. The behaviour of the attached materials in aqueous solution is parallel to the behaviour of the single fluorophoric polyamines. Comparisons are …

Interactions of diaryl-polyamines with nucleic acids. Allosteric effects with dinuclear copper complexes

Abstract A series of α,ω-diarylamines with a variable number of ethylenediamine units between terminal naphthylrings shows dramatic affinity changes towards double-stranded nucleic acids, particularly upon complexation with Cu(II) ions. Metal salts alone have under the applied conditions only a negligible effect. The affinity of the metal-free ligands towards nucleic acids shows significant differences to those of the underlying polyamines, with a reversed stabilization of DNA instead of the usually observed preference for RNA. The affinity changes and preliminary NMR studies are in line with intercalation of naphthylrings into the double-stranded nucleic acid, which is hampered by complex …

Energetics and Dynamics of Naphthalene Polyaminic Derivatives. Influence of Structural Design in the Balance Static vs Dynamic Excimer Formation

Two new fluorescent macrocyclic structures bearing two naphthalene (Np) units at both ends of a cyclic polyaminic chain were investigated with potentiometric, fluorescence (steady-state and time-resolved) and laser flash photolysis techniques. The fluorescence emission studies show the presence of an excimer species whose formation depends on the protonation state of the polyamine chains implying the existence of a bending movement (occurring in both the ground and in the first singlet excited state), which allows the two naphthalene units to approach and interact. For comparison purposes, one bis-chromophoric compound containing a rigid chain (piperazine unit) was also investigated. Its em…

Grafted squaramide monoamine nanoparticles as simple systems for sulfate recognition in pure water.

New simple systems formed by a chain containing a squaramide function and a quaternised amine group attached to boehmite or silica-coated boehmite nanoparticles are able to discriminate anions in pure water.

Empirical modeling of material composition and size in MOFs prepared with ligand mixtures

Systematic analyses of the composition and size of metal-organic frameworks built with Zn4O and terephthalic/amino-terephthalic acid mixtures, together with a kinetic assay, reveal how these ligands behave differently, which reveals the complexity of crystal growth in these frameworks and the ability to tune it on purpose.

Unravelling the modus operandi of phytosiderophores during zinc uptake in rice: the importance of geochemical gradients and accurate stability constants

Abstract Micronutrient deficiencies threaten global food production. Attempts to biofortify crops rely on a clear understanding of micronutrient uptake processes. Zinc deficiency in rice is a serious problem. One of the pathways proposed for the transfer of zinc from soils into rice plants involves deoxymugineic acid (DMA), a phytosiderophore. The idea that phytosiderophores play a wider role in nutrition of Poaceae beyond iron is well established. However, key mechanistic details of the DMA-assisted zinc uptake pathway in rice remain uncertain. In particular, questions surround the form in which zinc from DMA is taken up [i.e. as free aqueous Zn(II) or as Zn(II)–DMA complexes] and the role…

A new macrocyclic dipyrazolate salt of diazatetraester structure able to efficiently and selectively interact with psychotropic phenethylammonium salts

Abstract The equilibrium stability constants (Ks) of a series of ammonium pyrazolate complexes [L22−]2RN(R′)H2+ (7, R′=H and 8, R′=Me) formed from a new macrocyclic disodium dipyrazolate salt of diazatetraester structure 6[L22−] 2Na+ and ammonium salts [RNH3+X− or RN(Me)H2+X−] of psychotropic drugs and neurotransmitter catecholamines has been evaluated by electrochemical methods in DMSO solution. The resulting Ks values demonstrate that in general, the diazatetraester crown-derived dipyrazolate salt 6 exerts a stronger complexing effect over phenethylammonium ions than that of the dioxatetraester crown-derived disodium dipyrazolate salt 2 previously reported. Interestingly, complexes formed…

Homogeneous and supported copper complexes of cyclic and open-chain polynitrogenated ligands as catalysts of cyclopropanation reactions

CuI and CuII complexes of cyclic and open-chain polyaza compounds have been tested as catalysts in the benchmark cyclopropanation reaction of styrene with ethyl diazoacetate. In general, only small amounts of copper are needed to promote the reaction. The catalytic activity depends on the structure of the ligand, e.g. amine–amides are more efficient than polyamines, and on the oxidation state of copper, CuII being more active than CuI. Given that CuI is the active species, these changes of behavior must be related to the stabilities of the complexes. The nature of the counterion also has a noticeable influence on the catalytic activity, the role of which is discussed. XAS measurements sugge…

A Metal-Based Receptor for Selective Coordination and Fluorescent Sensing of Chloride

A scorpionate Zn2+ complex, constituted by a macrocyclic pyridinophane core attached to a pendant arm containing a fluorescent pyridyl-oxadiazole-phenyl unit (PyPD), has been shown to selectively recognize chloride anions, giving rise to changes in fluorescence emission that are clearly visible under a 365 nm UV lamp. This recognition event has been studied by means of absorption, fluorescence, and NMR spectroscopy, and it involves the intramolecular displacement of the PyPD unit by chloride anions. Moreover, since the chromophore is not removed from the system after the recognition event, the fluorescence can readily be restored by elimination of the bound chloride anion.

Thermodynamic and kinetic studies on the Cu2+ coordination chemistry of a novel binucleating pyridinophane ligandElectronic supplementary information (ESI) available: Table S1: observed rate constants for the acid-promoted decomposition of Cu2+ complexes with ligand L. Table S2: observed rate constants for the acid-promoted decomposition of Cu2+ complexes with macrocycle L1. Fig. S1: Variation of some selected 13C chemical shifts as a function of pH. See http://www.rsc.org/suppdata/dt/b2/b209013a/

The synthesis and coordination chemistry of the novel pyridine-functionalized ligand 2,6,9,12,16-pentaaza[17]-(2,6)pyridinophane (L1) is described. The compound behaves as a hexaprotic base in aqueous solution. NMR studies indicate a protonation pattern in which the sp2 pyridine nitrogen (N(py)) does not undergo a net protonation although it is involved in formation of hydrogen bonds. L1 forms mono and binuclear hydroxylated complexes. The crystal structure of [CuL1](ClO4)2 shows a square planar coordination for Cu2+ with the pyridine and the three central nitrogens of the chain forming the vertices of the square. The benzylic nitrogens could be occupying the axial positions of a strongly a…

Hydrogen and copper ion-induced molecular reorganizations in scorpionand-like ligands. A potentiometric, mechanistic, and solid-state study.

Two aza scorpionand-like macrocycles (L2 and L3) have been prepared. L2 consists of a tren amine with two of its arms cyclizized with a 2,6-bis(bromomethyl)pyridine. In L3, the remaining pendant arm has been further functionalized with a fluorophoric naphthalene group. X-ray data on the compounds [H(L3)]ClO4.H2O (1) and [H3(L3)](H2PO4)3.H2O (2) as well as solution studies (pH-metry, UV-vis, and fluorescence data) show the movement of the pendant arm as a result of the protonation degree of the macrocycles and of the formation of intramolecular hydrogen bonds. X-ray data on the complexes [Cu(L2)](ClO4)2]2.H2O (3) and [Cu(L3)](ClO4)2 (4) and solution studies on Cu2+ coordination show the impl…

Acid–base behaviour and binding to double stranded DNA/RNA of benzo[g]phthalazine-based ligands

The affinity and the binding mode of two benzo[g]phthalazine compounds, functionalized with one or two 2-(imidazole-4-yl)-ethylamine groups, to DNA and RNA models have been evaluated by means of UV-Vis, fluorescence and circular dichroism (CD) spectroscopies in combination with viscometry and molecular dynamics. Both organic molecules bind strongly to all nucleic acid models via the intercalation mode in the duplex structure, especially compound 1. Intriguingly, 1 exhibits different emission responses depending on the base composition of duplex DNA/RNAs, which points out the possibility of using it as a base selective nucleic acid probe. Moreover, the acid-base behaviour of both compounds h…

One-pot synthesis of polyaza[n]naphthalenophanes and polyaza[n]anthracenophanes

Abstract Pernosylated polyaza[n]cyclophanes 13–20 were prepared by a Richman-Atkins modified methodology. Deprotection under mild conditions gave polyaza[n]cyclophanes 21–28 . This methodology allows for the preparation of cyclophanes containing labile C-N bonds.

Development of Polyamine‐Substituted Triphenylamine Ligands with High Affinity and Selectivity for G‐Quadruplex DNA

Currently, significant efforts are devoted to designing small molecules able to bind selectively to guanine quadruplexes (G4s). These noncanonical DNA structures are implicated in various important biological processes and have been identified as potential targets for drug development. Previously, a series of triphenylamine (TPA)-based compounds, including macrocyclic polyamines, that displayed high affinity towards G4 DNA were reported. Following this initial work, herein a series of second-generation compounds, in which the central TPA has been functionalised with flexible and adaptive linear polyamines, are presented with the aim of maximising the selectivity towards G4 DNA. The acid-bas…

Macrocyclic Pyclen-Based Gd3+ Complex with High Relaxivity and pH Response

We report the synthesis and characterization of the macrocyclic ligand 2,2'-((2-(3,9-bis(carboxymethyl)-3,6,9-triaza-1(2,6)-pyridinacyclodecaphane-6-yl)ethyl)azanediyl)diacetic acid (H4L) and several of its complexes with lanthanide ions. The structure of the free ligand was determined using X-ray diffraction measurements. Two N atoms of the pyclen moiety in the trans position are protonated in the solid state, together with the exocyclic N atom and one of the carboxylate groups of the ligand. The relaxivity of the Gd3+ complex was found to increase from 6.7 mM-1 s-1 at pH 8.6 to 8.5 mM-1 s-1 below pH ≈ 6.0. Luminescence lifetime measurements recorded from H2O and D2O solutions of the Eu3+ …

Pb2+complexes of small-cavity azamacrocyclic ligands: thermodynamic and kinetic studies

The synthesis, acid-base behavior and Pb2+ coordination chemistry of the new aza-scorpiand like ligand 5-[2-(N-2-fluorenyl)ethylamino]-2,5,8-triaza[9]-2,6-pyridinophane (L1) have been studied by potentiometry, NMR and spectrofluorimetric titrations, and the results are compared with those obtained for the related compounds L2, lacking the fluorenyl group, and L3, the macrocycle lacking the pendant arm. The crystal structures obtained for complexes [PbL1][PbL1Cl](NO3)Cl2·4H2O (1) and [PbL3](ClO4)2 (2) reveal that the metal ion is located over the plane defined by the nitrogen atoms of the macrocyclic core due to its inability to accommodate the large Pb2+ ion in the macrocyclic cavity. For L…

Tetraaza-2,2′-biphenylophanes: larger is not always more flexible. The role of intramolecular H-bonding in polyazamacrocycles

Abstract Intramolecular H-bonding can explain the trends in conformational flexibility for tetraaza-2,2′-biphenylophanes obtained by NMR and molecular dynamics calculations.

Thermodynamics and fluorescence emission studies on potential molecular chemosensors for ATP recognition in aqueous solution †

The interaction of the open-chain polyamine N-(3-aminopropyl)-N′-[3-(anthrylmethyl)aminopropyl]ethane-1,2-diamine (L) with the relevant anionic forms of adenosine 5′-triphosphate (ATP), adenosine 5′-diphosphate (ADP) and adenosine 5′-monophosphate (AMP) is described. Unambiguous criteria for defining thermodynamic selectivity based on the use of effective stability constants are presented. The interaction of L and several other topologically similar polyammonium receptors with ATP has been shown to occur through electrostatic and π-stacking intermolecular forces. The π-stacking binding mode is modulated by the protonation degree of ATP as indicated by fluorescence emission titrations. Evide…

Supramolecular interactions of hexacyanocobaltate(III) with polyamine receptors containing a terminal anthracene sensor

Abstract The fluorescence emission properties of a series of chemosensors containing a polyamine receptor bearing an anthracene signaling unit were studied. The fluorescence emission intensity is dependent on the protonation degree of the receptor, the fully protonated form exhibiting the highest emission intensity. By removing protons from the nitrogens a quenching effect can be observed, due to an electron-transfer from the amine to the excited fluorophore. The rate constant of the quenching process is exponentially dependent on the distance of the nitrogen from which the electron is transferred (β=0.6 A−1). The ability of the chemosensors for signaling anions was tested through the model…

Fluorescent chemosensors containing polyamine receptors

Chemosensors have attracted interest in many different scientific fields, such as environmental chemistry, medicine, and the processing and storage of information. These molecular-scale devices have the advantage of working on the same spatial scale as the chemical structures that are responsible for macroscopic behaviour observed in the environment or those associated with health problems. Moreover, they allow the construction of molecular-scale devices for information storage. In this review, we describe a family of chemosensors based on a polyamine receptor and a fluorescent signalling unit. Polyamine receptors are water-soluble ambidentate receptors; they are able to coordinate either m…

Pertosylated polyaza[n](9,10)anthracenophanes

Abstract Pertosylated polyaza[n](9,10)antracenophanes have been obtained in high yields by a modification of the Richman-Atkins methodology. Molecular Mechanics calculations as well as the crystal structure of the N,N′,N″,N‴-Tetratosyl-2,6,9,13-tetraaza[14](9,10)anthracenophane 4 derivative reveal the existence of a well defined cavity where both the aromatic moiety and the nitrogen donor atoms converge. Reduced mobility of the aliphatic chain is also observed as well as the presence of some strain at the benzylic positions.

Electrochemistry of copper complexes with polyaza[n]paracyclophanes. Influence of ATP as an exogen ligand on the relative stability of the Cu(II) and Cu(I) oxidation states

Abstract Interaction of Cu 2+ with the macrocycle 2,6,9,13-tetraaza[14]paracyclophane (L) and ATP has been followed by pH-metric titration, cyclic voltammetry and differential pulse voltammetry (DPV). Mixed adduct species with various degrees of protonation were found to be stable for pH>4. In neutral and alkaline media reduction of mixed complexes occurs in a two-electron quasi-reversible step in contrast with binary Cu 2+ L complexes which display two successive one-electron couples. The potentiometric and voltammetric data suggest that in ternary adducts ATP binds to Cu 2+ ions through the phosphate chain and one N-site of the adenine ring system.

Self-assembly of 3,5-bis(ethoxycarbonyl)pyrazolate anions and ammonium cations of β-phenylethylamine or homoveratrylamine into hetero-double-stranded helical structures

Hydrogen-bonded double-stranded hetero-helices are formed when reacting sodium 3,5-bis(ethoxycarbonyl)pyrazolate with beta-phenethylammonium or homoveratrylammonium chloride, in which one of the strands is defined by the ammonium cations and the other one by the pyrazolate anions.

X-Ray characterization of 3-methyl-6,8-di(2-pyridyl)-[1,2,3]triazolo[5',1':6,1]pyrido[2,3-d]pyrimidine

Abarca Gonzalez, Belen. Belen.Abarca@uv.es ; Ballesteros Campos, Rafael, Rafael.Ballesteros@uv.es ; Chadlaoui, Mimoun, michad@alumni.uv.es ; Ramirez de Arellano Sanchez, Maria del Carmen, Ramirezdearellano@uv.es

Mn(II) complexes of scorpiand-like ligands. A model for the MnSOD active centre with high in vitro and in vivo activity

Manganese complexes of polyamines consisting of an aza-pyridinophane macrocyclic core functionalised with side chains containing quinoline or pyridine units have been characterised by a variety of solution techniques and single crystal x-ray diffraction. Some of these compounds have proved to display interesting antioxidant capabilities in vitro and in vivo in prokaryotic (bacteria) and eukaryotic (yeast and fish embryo) organisms. In particular, the Mn complex of the ligand containing a 4-quinoline group in its side arm which, as it happens in the MnSOD enzymes, has a water molecule coordinated to the metal ion that shows the lowest toxicity and highest functional efficiency both in vitro …

N-(2-methyl-indol-1H-5-yl)-1-naphthalenesulfonamide : a novel reversible antimitotic agent inhibiting cancer cell motility

Este es el post-print que se ha publicado de forma definitiva en: https://www.sciencedirect.com/science/article/abs/pii/S0006295216301423 A series of compounds containing the sulfonamide scaffold were synthesized and screened for their in vitro anticancer activity against a representative panel of human cancer cell lines, leading to the identification of N-(2-methyl-1H-indol-5-yl)-1-naphthalenesulfonamide (8e) as a compound showing a remarkable activity across the panel, with IC50 values in the nanomolar-to-low micromolar range. Cell cycle distribution analysis revealed that 8e promoted a severe G2/M arrest, which was followed by cellular senescence as indicated by the detection of senescen…

Anti-angiogenic drug loaded liposomes: Nanotherapy for early atherosclerotic lesions in mice.

Este artículo se encuentra disponible en la página web de la revista en la siguiente URL: https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0190540 También participan en la elaboración de este artículo científico: Aracely Calatayud-Pascual, Alicia López-Castellano, Elena P. Albelda, Enrique García-España, Luis Martí-Bonmatí, Juan C. Frias y M. Teresa Albelda. Fumagillin-loaded liposomes were injected into ApoE-KO mice. The animals were divided into several groups to test the efficacy of this anti-angiogenic drug for early treatment of atherosclerotic lesions. Statistical analysis of the lesions revealed a decrease in the lesion size after 5 weeks of treatment.

A tetraazahydroxypyridinone derivative as inhibitor of apple juice enzymatic browning and oxidation

Abstract Enzymatic browning in fruits and vegetables can produce undesirable colour changes and adversely affect the taste, flavour, and nutritional value. This fact poses a challenge to the food industry to apply appropriate inhibitors to control enzymatic browning to maintain food quality. Accordingly, this study aims to evaluate the effect of small mazamacrocyclic compounds modified with a hydroxypyridinone similar to kojic acid on enzymatic browning, total polyphenols and antioxidant activity in apple juice. The results showed how these compounds interact with the tyrosinase enzyme in a complex interaction inhibiting its activity. The hydroxypyridinone attached to the macrocycle (I1) wa…

Aryl-bis-(scorpiand)-aza receptors differentiate between nucleotide monophosphates by a combination of aromatic, hydrogen bond and electrostatic interactions.

Bis-polyaza pyridinophane scorpiands bind nucleotides in aqueous medium with 10–100 micromolar affinity, predominantly by electrostatic interactions between nucleotide phosphates and protonated aliphatic amines and assisted by aromatic stacking interactions. The pyridine-scorpiand receptor showed rare selectivity toward CMP with respect to other nucleotides, whereby two orders of magnitude affinity difference between CMP and UMP was the most appealing. The phenanthroline-scorpiand receptor revealed at pH 5 strong selectivity toward AMP with respect to other NMPs, based on the protonation of adenine heterocyclic N1. The results stress that the efficient recognition of small biomolecules with…

Hydrogen and Copper Ion Induced Molecular Reorganizations in Two New Scorpiand-Like Ligands Appended with Pyridine Rings

The synthesis of two new ligands constituted of a tris(2-aminoethyl)amine moiety linked to the 2,6 positions of a pyridine spacer through methylene groups in which the hanging arm is further functionalized with a 2-pycolyl (L1) or 3-pycolyl (L2) group is presented. The protonation of L1 and L2 and formation of Cu(2+) complexes have been studied using potentiometric, NMR, X-ray, and kinetic experiments. The results provide new information about the relevance of molecular movements in the chemistry of this kind of so-called scorpiand ligand. The comparison between these two ligands that only differ in the position of the substituent at the arm reveals important differences in both thermodynam…

A polyazacyclophane containing two biphenyl subunits as a versatile cation and anion receptor

Abstract The synthesis, protonation behaviour and coordination capabilities towards Cu 2+ , Zn 2+ and towards the nucleotides ATP and ADP of a cyclophane ditopic receptor 2,6,10,23,27,31-hexaaza[11,11](2,2′)biphenylophane containing two 2,2′-biphenylene spacers linked to the ends of 1,5,9-triazanonane chains are presented.

Linear, tripodal, macrocyclic: Ligand geometry and ORR activity of supported Pd(II) complexes

Abstract The novel ligand H3L designed to spontaneously adsorb onto MWCNT via electron-deficient pyrimidine residues and bind metal cations is used to prepare an oxygen reduction reaction (ORR) cathode catalyst based on supported Pd(II) complexes. Herein we report the synthesis of the ligand, its solution behaviour (protonation constants, binding constants for the test cation Cu(II), UV evidence of Cu(II) and Pd(II) complexes formation) and ORR performances together with XPS and STEM characterization. Tripodal nature of the H3L ligand frame it in-between previously studied macrocyclic and linear open chain ligands, allowing to draw meaningful comparisons.

An efficient β-turn directed cyclization of simple peptidomimetics

Abstract Chiral polyaza[n]para- and metacyclophanes are easily assembled starting from the appropriate bis(bromomethyl)arene and diamides obtained from aminoacids and alkylidenediamines. The corresponding ortho-derivatives could not be obtained. Molecular dynamics calculations suggest that those results can be explained through the participation of a β-turn like structure in the open chain intermediate, which is only important for para- and meta-derivatives.

Acid–base properties of functionalised tripodal polyamines and their interaction with nucleotides and nucleic acids

Novel, highly positively charged tripodal polyamines with appended heterocyclic moieties revealed an intriguing panel of protonation species within the biologically relevant range. Studied compounds bind nucleotide monophosphates by mostly electrostatic interactions but only the imidazole analogue showed selectivity toward UMP in respect to other nucleotides. Strong binding of all the studied compounds to both ds-DNA and ds-RNA is to some extent selective toward the latter, showing rather rare RNA over DNA preference.

Recognition, Transformation, Detection of Nucleotides and Aqueous Nucleotide-Based Materials

Intermolecular binding modes in a novel [1 + 1] condensation 1H-pyrazole azamacrocycle: a solution and solid state study with evidence for CO2 fixation.

The synthesis of a novel cyclophane (L1) consisting of a 1H-pyrazole moiety linked through methylene groups to a 1,5,9,13-tetraazadecane chain is described. As far as we know, this is one of the first reported syntheses of a [1 + 1] condensation 1H-pyrazole azamacrocyclic ligand. The crystal structures of the complexes [Cu2(H(H(-1)L1))(H(-1)L1)](ClO4)3·3.75H2O (1) and ([Cu2(H(H(-1)L1))(0.5)(H(-1)L1)(1.5)]2(ClO4)3Br2·4.2H2O (2) show that Cu(2+) coordination leads to formation of 2:2 Cu(2+):L dinuclear dimeric complexes in which the 1H-pyrazole units lose a proton behaving as bis(monodentate) bridging ligands. Unlike previously reported complexes of [2 + 2] pyrazole azamacrocycles, the pyrazo…

New molecular catalysts for ATP cleavage. Criteria of size complementarity

The interaction of the cyclophane receptor 2,5,8,11,14,17-hexaaza[18]metacyclophane (L) with the nucleotides ATP, ADP and AMP is described. L yields one of the largest rate enhancements for hydrolytic ATP cleavage observed in macrocyclic polyamines. The process is specific for the formation of ADP and involves a high degree of geometrical complementarity between host and guest species. The analogue compound 24-hydroxy-2,5,8,11,14,17-hexaaza[18]metacyclophane (L11) shows also a high degree of ATP activation. However, in this case deprotonation of the hydroxy group results in almost complete quenching of the ATPase activity above pH 7.0.

Cyclic voltammetric analysis of pH-dependent complex formation equilibria in anion coordination chemistry

A procedure to analyze pH-dependent complex formation equilibria from cyclic voltammetry is described. Application to adduct formation equilibria between [Fe(CN)(6)](4-) and [Fe(CN)(6)](3-) with different polyammonium receptors is discussed. Extension to the interaction of substrates such as ATP, NAD(+), NADP(+), and carboxylate ions with these receptors by means of competitive interaction with hexacyanoferrate(II) ion is presented.

In silico discovery of substituted pyrido[2,3-d]pyrimidines and pentamidine-like compounds with biological activity in myotonic dystrophy models

Myotonic dystrophy type 1 (DM1) is a rare multisystemic disorder associated with an expansion of CUG repeats in mutant DMPK (dystrophia myotonica protein kinase) transcripts; the main effect of these expansions is the induction of pre-mRNA splicing defects by sequestering muscleblind-like family proteins (e.g. MBNL1). Disruption of the CUG repeats and the MBNL1 protein complex has been established as the best therapeutic approach for DM1, hence two main strategies have been proposed: targeted degradation of mutant DMPK transcripts and the development of CUG-binding molecules that prevent MBNL1 sequestration. Herein, suitable CUG-binding small molecules were selected using in silico approach…

Synthesis and protonation behaviour of the macrocycle 2,6,10,13,17,21-hexaaza[22]metacyclophane. Thermodynamic and NMR studies on the interaction of 2,6,10,13,17,21-hexaaza[22]metacyclophane and on the open-chain polyamine 4,8,11,15-tetraazaoctadecane-1,18-diamine with ATP, ADP and AMP

Abstract The novel cyclophane receptor 2,6,10,13,17,21-hexaaza[22]metacyclophane (L) has been synthesised and characterised. The acid-base behaviour and interaction with ATP, ADP and AMP have been studied by potentiometry in 0.15 mol dm−3 at 298.1 K and multinuclear NMR. L presents in its protonated forms a molecular organization which enables its multipoint binding with nucleotides. Salt-bridge formation occur between the polyammonium sites of L and the phosphate chain of the nucleotides while π-stacking between the meta-phenylene subunit incorporated in the receptor and the adenine ring of the nucleotides.

A water molecule in the interior of a 1H-pyrazole Cu2+ metallocage

Water has a great tendency to associate through hydrogen bonding with water molecules or other hydrogen bond donor or acceptor groups. Here the case of a water molecule encapsulated in the interior of a metallocage receptor is presented. The association of four copper(II) ions and two aza-macrocyclic receptors in which two 1H-pyrazole units are connected by cadaverine diamines leads to the inclusion of a water molecule into the cage, as proved by X-ray analysis and infrared spectroscopy. The included water molecule shows no hydrogen bonding with any component of the cage presenting only a weak hydrogen bond with an oxygen atom of a perchlorate counter-anion. The IR stretching vibrations pre…

Exceedingly Fast Oxygen Atom Transfer to Olefins via a Catalytically Competent Nonheme Iron Species

El mateix article està publicat en alemany a l'edició alemanya d' 'Angewandte Chemie' (ISSN 0044-8249, EISSN 1521-3757), 2016, vol. 128, núm. 21, p.6418–6422. DOI http://dx.doi.org/10.1002/ange.201601396 The reaction of [Fe(CF3SO3)2(PyNMe3)] with excess peracetic acid at −40 °C leads to the accumulation of a metastable compound that exists as a pair of electromeric species, [FeIII(OOAc)(PyNMe3)]2+ and [FeV(O)(OAc)(PyNMe3)]2+, in fast equilibrium. Stopped-flow UV/Vis analysis confirmed that oxygen atom transfer (OAT) from these electromeric species to olefinic substrates is exceedingly fast, forming epoxides with stereoretention. The impact of the electronic and steric properties of the subs…

Efficient two-step synthesis of water soluble BODIPY–TREN chemosensors for copper(II) ions

Two simple fluorescent sensors for Cu(II) ions were synthesized in two reaction steps, using recently developed C–H functionalization reactions for boron dipyrrins, starting from a standard 8-aryl-BODIPY dye and a tris(2-aminoethyl)amine (TREN) ligand. At pH 5, the resulting BODIPY–TREN conjugates are demonstrated to be promising, highly selective, water soluble, Cu(II) sensors that can permeate the cell membrane. crosscheck: This document is CrossCheck deposited related_data: Supplementary Information identifier: Bram Verbelen (ORCID) identifier: Wim Dehaen (ORCID) copyright_licence: The Royal Society of Chemistry has an exclusive publication licence for this journal copyright_licence: Thi…

Receptors for Nucleotides

Recognition and activation of nucleotides by polyammonium receptors constitute an important target in supramolecular chemistry since the very beginning of this field. Nucleotides have three components: (i) the polyphosphate chain, (ii) the sugar moiety, and (iii) the nucleobase, which permit their multipoint binding through attractions between opposite charges, hydrogen bonding, π-stacking, CH–π interactions, and so on. In this chapter, different receptors for nucleotides, most but not all of them consisting polyamines, are examined, focusing on their molecular structure that enables different binding modes to be operated. Also, a number of examples of nucleotide binding through metal compl…

Heterocyclic Diamines with Leishmanicidal Activity.

Leishmaniasis is one of the world's most neglected diseases with a worldwide prevalence of 12 million people. There are no effective human vaccines for its prevention, and outdated drugs hamper treatment. Therefore, research aimed at developing new therapeutic tools to fight leishmaniasis remains a crucial goal today. With this purpose in mind, here, we present 10 new compounds made up by linking alkylated ethylenediamine units to pyridine or quinoline heterocycles with promising in vitro and in vivo efficacy against promastigote and amastigote forms of Leishmania infantum, Leishmania donovani, and Leishmania braziliensis species. Three compounds (2, 4, and 5) showed a selectivity index muc…

Influence of the chain length and metal : ligand ratio on the self-organization processes of Cu2+ complexes of [1 + 1] 1H-pyrazole azamacrocycles

Three new [1 + 1] macrocycles formed by the reaction of 1H-3,5-bis(chloromethyl)pyrazole with the tosylated amines 1,4,7,10-tetraazadecane (L1), 1,4,8,11-tetraazaundecane (L2) and 1,5,10,14-tetraazatetradecane (L3) are described. Potentiometric studies and HR-ESI-Mass spectrometry show the formation of dimeric binuclear Cu2+ complexes whose organization depends on the type of hydrocarbon chains connecting the amine groups. Furthermore, trinuclear or/and tetranuclear complexes are formed depending also on the length of the polyaminic bridge and on the sequence of the hydrocarbon chains. The crystal structures of the [2 + 2] [Cu2(H(H−1L2))2](ClO4)4·4H2O (1) and [Cu2(H−1L2)2](ClO4)2 (2) comple…

Azonia spiro polyaza macrocycles containing biphenyl subunits as anion and cation receptors

Abstract The reaction of N-Boc triprotected cyclam with bis(chloromethyl)biphenyl followed by the corresponding deprotection of the nitrogen atoms allows the preparation of receptor 3 containing an azonia spiro subunit. This receptor shows slightly increased basicity than cyclam, in particular for the formation of the appropriate triply charged species as a consequence of the reduced capacity of the structure present in 3 to stabilize the species with lower protonation degrees through the formation of intramolecular hydrogen bonds. The properties of 3 as a receptor for Cu2+ and Zn2+ and the anions derived from PO 4 3 − ( Pi ) , P 2 O 7 4 − ( PPi ) , P 3 O 10 5 − ( TPP ) and ATP have been st…

Cation and anion recognition characteristics of open-chain polyamines containing ethylenic and propylenic chains

Abstract The interaction of the polyamines 4,7,10,13-tetraazahexadecane-1,16-diamine (L1) and 4,7,10-triazatridecane-1,13-diamine (L2) with H + , Cu 2+ , Zn 2+ , Co 2+ and the nucleotides ATP, ADP and AMP has been followed by NMR and potentiometric studies performed at 298.1 K in 0.15 mol dm −3 NaClO 4 . The influence of the different sequences of hydrocarbon chains and chelate rings present in the ligands on the values of the protonation constants, the stability of the metal ion complexes as well as in the co-ordination to nucleotides is analysed. The formation of mixed complexes has been investigated for the system Cu 2+ –L1–AMP.

Guest-Induced Selective Functionalization of Polyaza[n]paracyclophanes

A new strategy to the preparation of selectively functionalized polyazamacrocycles is presented. Polyaza[n]paracyclophane receptors are able to efficiently direct their own selective functionalization upon interaction with simple guests such as metal cations. This enables the preparation of novel receptors functionalized at one of the benzylic nitrogen atoms with a variety of groups. Selective difunctionalization at both benzylic positions can also be achieved in this way.

In vitro antileishmanial activity of aza-scorpiand macrocycles. Inhibition of the antioxidant enzyme iron superoxide dismutase

The in vitro leishmanicidal activity of a series of nine aza-scorpiand-like macrocycles, recently synthesized, was tested on Leishmania infantum, Leishmania braziliensis and Leishmania donovani parasites, using promastigotes and intracellular amastigotes forms. The cytotoxicity of the tested compounds on J774.2 macrophage cells was also measured. Four of the tested compounds (1, 2, 8 and 9) showed selectivity indexes higher than those of the reference drug Glucantime for the three Leishmania species. Moreover, the data on infection rates and on amastigotes showed that compounds 1, 2, 8 and 9 are the most active against the three Leishmania species. The changes in the excretion product profi…

VIOLURATO COMPLEXES OF Cr(III). SYNTHESIS AND CHARACTERIZATION. PROTONATION-DEPROTONATION EQUILIBRIA OF THE COORDINATED LIGANDS. EVIDENCE OF THE COORDINATION OF VIOLURIC ACID AS A NEUTRAL LIGAND

Abstract The formation of violurato complexes of Cr(III) has been studied in aqueous solution. Two compounds, [Cr(H2V)3].5H2O and Na[Cr(H2V)2(OH)2].4H2O have been synthesized and characterized. [Cr(H2V)3] behaves in aqueous solution as a triprotic acid but it can also add a proton yielding [Cr(H2V)2(H3V)]+. The acidity constants of this species have been determined: pKa1 =3.32, pKa2 =4.25, pKa3 =4.83 and pKa4 =6.99 (25°C, 0.1 M NaC1O4). [Cr(H2V)2(OH)2]− undergoes a deprotonation of the two H2V− ligands and a protonation of the hydroxo ligands. The acidity constants of [Cr(H2V)2(H2O)2]+ have been also determined: pKa1 =3.5, pKa2 =4.6, pKa3 =7.1 and pKa4 =9.2 (25°C, 0.1 M NaC1O4). The coordin…

Protonation, coordination chemistry, cyanometallate "supercomplex" formation and fluorescence chemosensing properties of a bis(2,2'-bipyridino)cyclophane receptor.

A new polyazamacrocycle (L) containing two 2,2'-bipyridino (bpy) units, where the heteroaromatic nitrogen atoms point outwards from the macrocyclic cavity, was synthesized and characterized by elemental analysis, ESI-MS, (1)H and (13)C NMR, FTIR and TGA. Five protonation constants involving aliphatic nitrogens with log K in the range 9.39-3.07 were determined by potentiometry and NMR and a sixth protonation (log K = 2.2) involving a bipyridine moiety could be detected by UV-Vis and NMR titrations. The interaction of L with the cyanometallate anions [Pt(CN)4](2-) and [Co(CN)6](3-) was studied by potentiometry yielding respectively log K values in the ranges 4.0-6.4 and 5.2-10.5, covering pro…

Lanthanide complexes as imaging agents anchored on nano-sized particles of boehmite

International audience; The synthesis of boehmite nanoparticles modified with lanthanides (Eu, Tb and Gd) is described. Their synthesis, characterization and in vitro assays with HeLa cells were performed. The nuclear magnetic relaxation dispersion (NMRD) profiles of the two chelating moieties were studied. Imaging data from laser scanning confocal fluorescence microscopy and flow cytometry revealed that the nanoscaffolds were taken up by the cells, distributed throughout the cytoplasm and showed no toxicity. This platform could represent an alternative to silica-based inert matrices as imaging vehicles.

Molecular Rearrangement of an Aza-Scorpiand Macrocycle Induced by pH: A Computational Study †

Rearrangements and their control are a hot topic in supramolecular chemistry due to the possibilities that these phenomena open in the design of synthetic receptors and molecular machines. Macrocycle aza-scorpiands constitute an interesting system that can reorganize their spatial structure depending on pH variations or the presence of metal cations. In this study, the relative stabilities of these conformations were predicted computationally by semi-empirical and density functional theory approximations, and the reorganization from closed to open conformations was simulated by using the Monte Carlo multiple minimum method Financial support by the Spanish Ministerio de Economía y Competitiv…

Supramolecular complexation for environmental control

Supramolecular complexes offer a new and efficient way for the monitoring and removal of many substances emanating from technical processes, fertilization, plant and animal protection, or e.g. chemotherapy. Such pollutants range from toxic or radioactive metal ions and anions to chemical side products, herbicides, pesticides to drugs including steroids, and include degradation products from natural sources. The applications involve usually fast and reversible complex formation, due to prevailing non-covalent interactions. This is of importance for sensing as well as for separation techniques, where the often expensive host compounds can then be reused almost indefinitely. Immobilization of …

Steady-state fluorescence emission studies on polyazacyclophane macrocyclic receptors and on their adducts with hexacyanocobaltate(III)

The steady-state fluorescence emission spectra of the azacyclophanes 2,5,8,11-tetraaza[12] paracyclophane (L1), 2,6,9,13-tetraaza[14]paracyclophane (L2), 14,15,17,18-tetramethyl-2,5,8,11-tetraaza[12]paracyclophane (L3) and 16,17,19,20-tetramethyl-2,6,9,13-tetraaza[14]paracyclophane (L4) as a function of pH have been measured. The fully protonated species of each cyclophane gives the highest fluorescence-emission quantum yield. The shapes of the titration curves have been explained by the existence of an electron-transfer quenching effect from a non-protonated amine to the benzene chromophore. This effect is greater for macrocycles in which the first deprotonated amine group is closer to the…

Addressing selectivity criteria in binding equilibria

Abstract Chemical systems, in particular those involving biological and environmental backgrounds, develop through selective processes which are determined by multiple equilibria. Several methods that have been developed to assess thermodynamic selectivity in binding equilibria, including the analysis of selectivity coefficients, the use of calculated species distribution diagrams, selectivity diagrams, and conditional stability constants, are reviewed in this paper with reference to examples mainly related to chemical systems of biological and/or environmental concern. Also the concept of binding affinity has been dealt with, since binding selectivity in equilibrium systems relates to the …

Synthesis, Characterization, and Cu(2+) Coordination Studies of a 3-Hydroxy-4-pyridinone Aza Scorpiand Derivative.

The synthesis, acid-base behavior, and Cu(2+) coordination chemistry of a new ligand (L1) consisting of an azamacrocyclic core appended with a lateral chain containing a 3-hydroxy-2-methyl-4(1H)-pyridinone group have been studied by potentiometry, cyclic voltammetry, and NMR and UV-vis spectroscopy. UV-vis and NMR studies showed that phenolate group was protonated at the highest pH values [log K = 9.72(1)]. Potentiometric studies point out the formation of Cu(2+) complexes of 1:2, 2:2, 4:3, 1:1, and 2:1 Cu(2+)/L1 stoichiometries. UV-vis analysis and electrochemical studies evidence the implication of the pyridinone moieties in the metal coordination of the 1:2 Cu(2+)/L1 complexes. L1 shows …

Voltammetry of microparticles, scanning electrochemical microscopy and scanning tunneling microscopy applied to the study of dsDNA binding and damage by scorpiand-like polyamine receptors

Abstract Microparticulate deposits of scorpiand-like azamacrocyclic receptors (L1–L4) attached to graphite electrodes provide distinctive voltammetric features in contact with aqueous DNA solutions at biological pH, denoting the formation of DNA surface complexes. This voltammetry allows for screening dsDNA, ssDNA and G-Quadruplex DNA using L4-modified electrodes. Scanning electrochemical microscopy and scanning tunneling microscopy examination of dsDNA fibers attached to the substrate electrode in contact with DMSO solutions containing ferrocene and receptor indicate that a synergic effect is exerted between electrochemically generated ferrocenium ion and the receptors so that they increas…

Water and oxoanion encapsulation chemistry in a 1H-pyrazole azacryptand

Anion complexes of the cryptand built with the tripodal amine tris(2-aminoethyl)amine, known as tren, with water and several oxoanions of biological and environmental interest (nitrate, sulfate, phosphate, perchlorate and arsenate) have been crystallized from aqueous solution and resolved with single-crystal X-ray diffraction. All crystals show guest species encapsulated in the interior of the cavity as well as, in some cases, sitting in the grooves defined by the arms of the macrocycle. Hydrogen bonding and electrostatic interactions play a major role in anion binding to the host. The macrocycle is able to encapsulate anions in a wide range of protonation degrees. Solution studies have bee…

Electrochemical determination of the stability of complexes formed by proton-ionizable ligands of 3,5-disubstituted 1H-pyrazole with phenethylamine

The application of two extreme models for diffusion in two-component systems to electrochemically determine equilibrium constants is discussed. The application of cyclic voltammetric, diferential pulse and rotating-disc electrode voltammetric data to elucidate the stoichiometry and formation constant of complex species by applying a generalization of the molar-ratio method is described. Molar-ratio experiments permit the distinction between the limiting diffusive regimes. The values of the equilibrium stability constants for complexation of phenethylamine and phenethylammonium ions by a 26-membered dioxotetraester crown of 3,5-disubstituted 1H-pyrazole as free ligand 1[L] and as dipyrazolat…

Synthetic methods for the preparation of polystyrene resins containing chiral polyamine chains

Abstract The preparation of functionalized polystyrene-divinylbenzene resins containing functional groups derived from polyamine aliphatic chains has been studied. Best results are always obtained by direct alkylation of the polyamine with Merrifield's polymers, but double alkylation at both end of the polyamine is observed. The procedure is useful for the preparation of polymer containing different chiral and non-chiral polyamine functionalities.

Thermodynamic and fluorescence emission studies on chemosensors containing anthracene fluorophores. Crystal structure of {[CuL1Cl]Cl}2·2H2O [L1 = N-(3-aminoprophyl)-N′-3-(anthracen-9-ylmethyl)aminopropylethane-1,2- diamine]

The co-ordination capabilities toward hydrogen ions, Co2+, Ni2+, Cu2+, Zn2+ and Cd2+ of the novel receptor 2,6,9,13-tetraaza[14](9,10)anthracenophane (L) and of its open-chain counterpart N-(3-aminopropyl)-N′-3-(anthracen-9-ylmethyl)aminopropylethane-1,2-diamine (L1) is described. Stepwise protonation constants of the cyclic receptor (L) are lower than those of the open-chain receptor (L1) . Quenching effects of the fluorescence emission occur upon first and second deprotonation of L and upon second deprotonation of L1. Stability constants of the Co2+, Ni2+, Cu2+, Zn2+ and Cd2+ complexes follow the Irving–Williams trend and are intermediate between those of triethylenetetraamine with termin…

Toward a Rational Design of Polyamine-Based Zinc-Chelating Agents for Cancer Therapies.

In vitro viability assays against a representative panel of human cancer cell lines revealed that polyamines L1a and L5a displayed remarkable activity with IC50 values in the micromolar range. Preliminary research indicated that both compounds promoted G1 cell cycle arrest followed by cellular senescence and apoptosis. The induction of apoptotic cell death involved loss of mitochondrial outer membrane permeability and activation of caspases 3/7. Interestingly, L1a and L5a failed to activate cellular DNA damage response. The high intracellular zinc-chelating capacity of both compounds, deduced from the metal-specific Zinquin assay and ZnL2+ stability constant values in solution, strongly sup…

Electrochemistry of copper complexes with macrocyclic polyamines containing pyrazole units.

The voltammetric behaviour of bi- and mono-nuclear complexes formed in solution by Cu(2+) with three polyazacyclophanes containing pyrazole units in aqueous solution is described. Cyclic and square wave voltammetric responses at glassy carbon electrodes indicate that the reduction of copper-macrocycle complexes in solution takes place in two successive one-electron per Cu transfer processes coupled with preorganization and protonation reactions that mimic the behaviour of superoxide dismutase. The electrochemistry of ternary Cu(2+)-receptor-dopamine complexes exhibits significant differences with respect to the protection of the neurotransmitter from post-electron transfer cyclization react…

Cu2+ Coordination Properties of a 2-Pyridine Heptaamine Tripod: Characterization and Binding Mechanism

The synthesis, protonation, and Cu(2+) coordination chemistry of a tripodal heptaamine ligand (L(1)) functionalized with 2-pyridine fragments at the ends of its three branches are reported. L(1) presents six relatively high protonation constants followed by much more reduced constant that as indicated by the UV-vis and NMR data, occur on the pyridine fragments. p[H]-metric, ESI/MS(+), EPR and UV-vis data show that L(1) is able to form mono-, di-, and trinuclear Cu(2+) complexes. Slippage movements and molecular reorganizations have been observed to occur as a function of p[H] in the 1:1 Cu(2+) complexes. The kinetic studies showed that the complex formation is fast and proceeds through a di…

Complex formation equilibria between the acetazolamide ((5-acetamido-1,3,4-thiadiazole)-2-sulphonamide), a potent inhibitor of carbonicanhydrase, and Zn(II),Co(II), Ni(II) and Cu(II) in aqueous and ethanol-aqueous solutions

Abstract The stability constants for the equilibrium of complexation between acetazolamide and the divalent metal ions copper(II), nickel(II), zinc(II), and cobalt(II) have been determined by potentiometry both in water and in water-ethanol 50 vol. % solutions in 0.15 mol dm −3 NaNO 3 at 25°C. This mixed solvent has been used in order to obtain higher concentrations of acetazolamide in solution. For copper(II) and nickel(II), the binuclear species [Cu 2 (Acm) 2 ] and [Ni 2 (Acm) 3 ] 2− are detected in both solvents together with hydroxo species. The values of the stability constants are always higher in the mixed solvent than in water. For cobalt(II) and zinc(II), while in aqueous solution …

Methylation as an effective way to generate SOD-activity in copper complexes of scorpiand-like azamacrocyclic receptors

Abstract Methylation of the secondary amine groups of a scorpiand-type ligand consisting of a pyridine spacer connected through methylene groups to a tris(2-aminomethyl) unit with the pendant arm further functionalised with a 3-pyridine unit leads to a ligand whose Cu(II) complex exhibits threefold enhanced SOD activity with respect to the non-methylated ligand. Potentiometric studies indicate the formation of [CuL] 2+ species with a stability three orders of magnitude lower than that formed with the related non-methylated ligand. Kinetic studies indicate that methylation of the secondary nitrogens causes a deceleration of both the complex formation and the acid-induced dissociation of the …

Revealing interactions between polyaza pyridinophane compounds and DNA/RNA polynucleotides by SERS spectroscopy

Surface-enhanced Raman scattering spectroscopy (SERS) in the near-infrared region had been applied to study interactions of polyaza pyridinophanes with single stranded RNA and double stranded DNA and RNA polynucleotides. Studied compounds, PYPOD and PHENPOD, differed in the central aromatic moiety, pyridine and phenanthroline, respectively, which linked two cyclic amines. An intense scattering was obtained from molecules adsorbed onto the silver nanoparticles, showing nonlinear concentration dependence in the 6.5 × 10−8−6.5 × 10−5 M range. New bands in spectra of PYPOD/polynucleotide and PHENPOD/polynucleotide mixtures were assigned to vibrational modes of polynucleotide moieties involved i…

Dopamine interaction with a polyamine cryptand of 1H-pyrazole in the absence and in the presence of Cu(ii) ions. Crystal structure of [Cu2(H−1L](ClO4)3·2H2O

The crystal structure of the binuclear Cu2+ complex [Cu2(H−1L)](ClO4)3 ·2H2O of the cryptand L = 1,4,7,8,11,14,17,20,21,24,29,32,33,36-tetradecaazapentacyclo[12.12.12.1 6,9.119,22,1,31,34]hentetraconta-6,9(41), 19(40), 21,31,34(39)-hexaene is presented; evidence for the formation in solution of binary L–dopamine and ternary Cu2+–L–dopamine complexes is presented.

Iron(II) Complexes with Scorpiand-Like Macrocyclic Polyamines: Kinetico-Mechanistic Aspects of Complex Formation and Oxidative Dehydrogenation of Coordinated Amines.

The Fe(II) coordination chemistry of a pyridinophane tren-derived scorpiand type ligand containing a pyridine ring in the pendant arm is explored by potentiometry, X-ray, NMR, and kinetics methods. Equilibrium studies in water show the formation of a stable [FeL]2+ complex that converts to monoprotonated and monohydroxylated species when the pH is changed. A [Fe(H–2L)]2+ complex containing an hexacoordinated dehydrogenated ligand has been isolated, and its crystal structure shows the formation of an imine bond involving the aliphatic nitrogen of the pendant arm. This complex is low spin Fe(II) both in the solid state and in solution, as revealed by the Fe–N bond lengths and by the NMR spect…

Metals in supramolecular chemistry

Abstract Metals have played a fundamental role in the development of supramolecular chemistry. The main steps taken from the pre-supramolecular age to the present time are retraced with a brief description of salient examples from the unconscious use of gold nanoparticle in the preparation of the Lycurgus cup (5th or 4th century B.C.) to the modern use of metals as templates, for the preparation of large self-assembled structures, of molecular sensors, switches, motors and machines, for mimicking biological processes, for tissue and organ imaging or for the application of the Boolean logic at the molecular level.

Coordination Chemistry of Cu2+ Complexes of Small N-Alkylated Tetra-azacyclophanes with SOD Activity

A new tetraaza-pyridinophane macrocycle (L1) N-alkylated with two isopropyl and one methyl groups symmetrically disposed has been prepared and its behavior compared with those of the unsubstituted pyridinophane (L3) and the related compound with three methyl groups (L2). The protonation studies show that, first, a proton binds to the central methylated amine group of L1, while, second protonation leads to a reorganization of the protons that are at this stage attached to the lateral isopropylated amines. The X-ray structure of [HL1]+ agrees with the UV–vis and NMR studies as well as with the results of DFT calculations. The stability of the Cu2+ complexes decreases on increasing the bulkine…

<strong>Synthesis and Platinum (II) Complexes of Different Polyazacyclophane Receptors</strong>

During the last years, research on coordination chemistry of platinum has aroused great interest due to their potential biological applications. Herein, we report the interaction of PtCI42- with different polyazacyclophanes containing a pyridine unit as aromatic spacer. Formation of complexes has been studied by 1H and 195Pt NMR spectroscopy. Analysis of the recorded spectra of D2O solutions containing L and PtCl42- in a 1:1 molar ratio at acidic pH shows the evolution with time of the 1H and 195Pt signals. Different crystal structures have been solved by X-ray diffraction analysis. At acidic pHs, the metal ion is coordinated by the central amino group of the macrocyclic cavity and three ch…

Nitrate Encapsulation within the Cavity of Polyazapyridinophane. Considerations on Nitrate−Pyridine Interactions

Interaction of nitrate anions with a cyclophane (L) containing two pyridine units connected to two diethylenetriamine bridges through methylene positions is reported both in pure water and in the solid state. The crystal structure of [H4L](NO3)4 shows that one of the nitrate anions resides in the macrocyclic cavity forming two sets of bifurcated hydrogen bonds with the four protonated amino groups of the macrocycle. This anion is symmetrically placed in the middle of the pyridine rings with distances between its nitrogen atom and the centroids of the ring of 3.58 A. Despite this location, calculations by theoretical analysis were carried out to confirm whether the stabilizing effect is due …

Boehmite Supported Pyrene Polyamine Systems as Probes for Iodide Recognition

New organic–inorganic fluorescent probes made by attaching the tripodal polyamine (tris(2-aminoethyl))amine (tren), propylamine, or diethylenetriamine functionalized with pyrene as a fluorophore to an γ-aluminum oxohydroxide matrix have been prepared and studied both in solution and supported on the surface of boehmite nanoparticles. Both kinds of systems have been revealed as sensitive and selective fluorescence turn-off chemosensors for iodide in aqueous solution with an estimated detection limit that reaches 36 ppb. The recognition characteristics and photophysical properties of these molecules are essentially preserved when they are grafted to the surface of the particles. Since the nan…

A hybrid catalyst for decontamination of organic pollutants based on a bifunctional dicopper(II) complex anchored over niobium oxyhydroxide

Abstract This article describes the preparation and characterization of a hybrid oxidation catalyst for decontamination of organic pollutants which involves a bifunctional dicopper(II) complex and the niobium(V) oxyhydroxide as the active species, the later one being also a solid support. The pH range for the existence of the active species was determined by potentiometric and UV–vis spectroscopy at 25 °C and 0.15 M NaCl in a H 2 O/EtOH (70:30 v/v) solvent mixture containing copper(II) and the ligand N , N -2,2′-ethylenediphenylenebis(oxamic acid) (H 4 L). As far as the hybrid material is concerned, FTIR, FT-Raman, TEM and SEM images, surface area and TG/DTA analyses showed the occurrence o…

Synthesis and Cu(II) coordination of two new hexaamines containing alternated propylenic and ethylenic chains: Kinetic studies on pH-driven metal ion slippage movements

Abstract The synthesis of the open-chain and cyclic polyamines, 1,5,8,12,15,19-hexaazaheptadecane (L1) and 2,6,9,13,16,20-hexaaza[21]-(2,6)-pyridinophane (L2), are described. The protonation constants and interaction constants with Cu(II) have been determined by potentiometric measurements carried out at 298.1 K in 0.15 mol dm −3 NaClO 4 . The values obtained are discussed as a function of the open-chain or cyclic nature of the ligands and compared with analogous polyamines containing different sets of hydrocarbon chains between the nitrogen donors. Kinetic studies on the acid-promoted dissociation of the Cu(II) complexes indicate that the mono and binuclear complexes of L1 decompose with d…

Equilibrium and Kinetic Properties of Cu II Cyclophane Complexes: The Effect of Changes in the Macrocyclic Cavity Caused by Changes in the Substitution at the Aromatic Ring

The o-B232, m-B232 and p-B232 cyclophanes result from attaching the terminal amine groups of 1,4,8,11-tetraazaundecane (232) to the benzylic carbons of the corresponding o-, m- or p-xylanes. The cavity size of these cyclophanes changes moderately as a consequence of the substitution at the aromatic ring. The effects caused by these changes on the equilibrium constants for protonation and CuII complex formation of the cyclophanes are analyzed and compared with those of the noncyclic 232 polyamine. All three cyclophanes form mononuclear complexes, but only o-B232 is able to coordinate to CuII through the four amine groups simultaneously, whereas m-B232 and p-B232 can only use three nitrogen d…

Scorpiand-like azamacrocycles prevent the chronic establishment of Trypanosoma cruzi in a murine model.

Chagas disease is today one of the most important neglected diseases for its upcoming expansion to non-endemic areas and has become a threat to blood recipients in many countries. In this study, the trypanocidal activity of ten derivatives of a family of aza-scorpiand like macrocycles is evaluated against Trypanosoma cruzi in vitro and in vivo murine model in which the acute and chronic phases of Chagas disease were analyzed. The compounds 4, 3 and 1 were found to be more active against the parasite and less toxic against Vero cells than the reference drug benznidazole, 4 being the most active compound, particularly in the chronic phase. While all these compounds showed a remarkable degree …

Polyaza[n](1,4)naphthalenophanes and polyaza[n](9,10)anthracenophanes

Abstract A series of polyaza[n](1,4)naphthalenophanes and polyaza[n](9,10)anthracenophanes have been prepared by using the Fukuyama's protecting group (2- or 4-nitrophenyl sulfonyl) in a one-pot cyclization–deprotection reaction. Global yields for the purified products are comparable with those obtained for other polyazacyclophanes using the tosyl group as the amine protecting group. Their structural study has been carried-out by NMR showing a high rigidity for the smaller cycles and a more dynamic behaviour for the largest member of the series. The free energy barrier for the rotational equilibrium for compound 25 is about 3 kcal/mol lower than that calculated for analogous N-tosylated mac…

Luminescent supramolecular heterometallic macrocycles and their encapsulation on cholate gels

The metal complex formed by coordination of Zn(II) to 1,7-bis(4-methylpyridine)-4-(2- naphthylmethyl)-1,4,7-triazaheptane (ZnL2+) was reacted in aqueous solution with [Pd(NO3)2(en)] and [Pt(NO3)2(en)] salts to form the self-assembled heterometallic macrocycles [Zn2L2Pd2(en)2]8+ and [Zn2L2Pt2(en)2]8+, respectively. Pd(II) and Pt(II)- coordination modulates the original emission of ZnL2+ arising from the presence of the naphthalene chromophore and the formation of the macrocycles can be monitored due to the PET process occurring with coordination of Pd(II) and Pt(II) to the pyridine units of ZnL2+. Additionally, several studies reveal that these heteromacrocycles can be encapsulated in Zn(II)…

Violurato complexes of nickel(II). Formation equilibria. Deprotonation equilibria of the coordinated ligands and related stereochemical changes

The formation equilibria of nickel(II) violurato-complexes in water and dimethylsulphoxide-water (80∶20) as well as deprotonation of the coordinated ligands and related stereochemical changes are reported. The stability constants of the Ni2+-H2V− complexes logβ1=5.06, Iogβ2=9.38, logβ3=12.98 as well as the acidity constants of the [Ni(H2V)3]− complex, logβj1= 8.37, logβj2=15.76, logβj3=22.37 are determined at 25 °C and 0.1M NaClO4. A new violurato-complex of Ni2+, Na4[Ni(HV)3]5H2O, is isolated and characterized.

Polyaza[n]paracyclophanes as synthetic models of Zn containing enzymes. The role of a non coordinated nitrogen atom in the proximity of the metal

Abstract 2,6,9,13-Tetraaza[14]paracyclophane ( 3, B323 ) represents a simple model for Zn containing enzymes like HCAII which possess additional reactive groups in the proximity of the metal center. The Zn 2+ . 3 complex shows notable catalytic activity for the hydrolysis of p -nitrophenyl acetate. Structural modifications of 3 which affect to the non coordinated nitrogen atom greatly modify the catalytic activity of the receptor.

Tripyridinophane Platform Containing Three Acetate Pendant Arms: An Attractive Structural Entry for the Development of Neutral Eu(III) and Tb(III) Complexes in Aqueous Solution

We report a detailed characterization of Eu3+ and Tb3+ complexes derived from a tripyridinophane macro cycle bearing three acetate side arms (H3tpptac). Tpptac3- displays an overall basicity (Σ log KiH) of 24.5, provides the formation of mononuclear ML species, and shows a good binding affinity for Ln3+ (log KLnL = 17.5-18.7). These complexes are also thermodynamically stable at physiological pH (pEu = 18.6, pTb = 18.0). It should be noted that the pGd value of Gd-tpptac (18.4) is only slightly lower than that of commercially available MRI contrast agents such as Gd-dota (pGd = 19.2). Moreover, a very good selectivity for these ions over the endogenous cations (log KCuL = 14.4, log KZnL = 1…

A dinucleating ligand which promotes DNA cleavage with one and without a transition metal ion.

The dinucleating ligand L (1,3-bis[bis(pyridin-2-ylmethyl)amino]propan-2-ol) combined with metal ions efficiently cleaves DNA when M : L is 1 : 1 (M = Co(II) or Fe(III)) at pH 5.5–7.0, with free L being more active at acidic pH than when bound to Zn(II), Cu(II) or Ni(II) at neutral pH.

Monoamide Derivatives of EDTA Incorporating Pendent Carboxylates or Pyridyls: Synthesis, Metal Binding, and Crystal Structure of a Dinuclear Ca2+ Complex Featuring Bridging Na+ Ions

EDTA is a powerful, cheap and widely-used chelating unit for a large range of metal ions. To link it covalently to other molecules, the formation of an amide bond using one of the carboxylates is an attractive and simple approach, even though it may compromise metal ion binding as one of the four carboxylate donors is lost. Here we undertake a quantitative study of the metal ion binding of two new mono-amide derivatives of EDTA, namely AmGly1 and AmPy1, featuring an additional coordinating carboxylate or pyridyl group in the amide, respectively. The compounds are conveniently synthesised through alkylation of the tris-t-butyl ester of ethylenediamine-triacetic acid with the appropriate α-ch…

CuIIand ZnIICoordination Chemistry of Pyrazole‐Containing Polyamine Receptors − Influence of the Hydrocarbon Side Chain Length on the Metal Coordination

The synthesis of a new macrocyclic receptor (L 4 ) containing two 3,5-dimethylpyrazole units connected by dipropylenetriamine bridges is reported for the first time; pH-metric titrations indicate that L 4 shows six protonation steps in the pH range 2-11. In the absence of metal ions, the pyrazole moieties are not involved in acid-base processes in this pH range. Addition of Cu I I and Zn I I results in deprotonation of the pyrazole moieties which act as bis(monodentate) η 1 :η 1 ligands. This induced deprotonation occurs at higher pH values than in the complexes of the analogous ligand containing diethylenetriamine bridges (L 1 ). The crystal structures of [Cu 2 (H - 2 L 4 )](ClO 4 ) 2 and …

Crystalline self-assembly induced by aromatic edge-to-face interactions: the crystal structure of 2,6,6,10-tetrabenzyl-2,10-diaza-6-azonia[11]paracyclophane bromide

The crystal structure of 2,6,6,10-tetrabenzyl-2,10-diaza-6-azonia[11]paracyclophane bromide reveals several intermolecular aromatic edge-to-face interactions which are important in the three-dimensional growing of the crystalline structure. Molecular dynamics and semiempirical studies indicate that the conformer found in the crystal is not the most stable in solution confirming the important role that edge-to-face interactions play in the structural arrangement found in the solid state.

In vitro and in vivo trypanosomicidal activity of pyrazole-containing macrocyclic and macrobicyclic polyamines: their action on acute and chronic phases of Chagas disease.

The in vitro and in vivo anti- Trypanosoma cruzi activity of the pyrazole-containing macrobicyclic polyamine 1 and N-methyl- and N-benzyl-substituted monocyclic polyamines 2 and 3 was studied. Activity against both the acute and chronic phases of Chagas disease was considered. The compounds were more active against the parasite and less toxic against Vero cells than the reference drug benznidazole, but 1 and 2 were especially effective, where cryptand 1 was the most active, particularly in the chronic phase. The activity results found for these compounds were complemented and discussed by considering their inhibitory effect on the iron superoxide dismutase enzyme of the parasite, the nature…

New sensing devices part 1: indole-containing polyamines supported in nanosized boehmite particles

The synthesis, characterisation and optical properties of new sensing systems made by attaching different polyamine chains functionalised with an indole fluorophore to a boehmite matrix is reported for the first time. Firstly, a family of tri(alkoxy)alkylpolyaminosilanes have been reacted with indole-3-carboxaldehyde to form the corresponding Schiff bases which were reduced with sodium borohydride. The anchoring to the surface of the boehmite nanoparticles was carried out by reacting the precursors with the hydroxyl groups available in the surface of the support. The characterisation of the materials by elemental microanalysis, X-ray powder diffraction, CP-MAS 29Si NMR and electron microsco…

CO2 Fixation by Cu2+ and Zn2+ complexes of a terpyridinophane aza receptor. Crystal structures of Cu2+ complexes, pH-metric, spectroscopic, and electrochemical studies.

The synthesis of the terpyridinophane-type polyamine 2,6,9,12,16-pentaaza[17]-(5,5' ')-cyclo-(2,2':6',2' ')-terpyridinophane heptahydrobromide tetrahydrate (L.7HBr.4H2O) is described. L presents six protonation constants with values in the range 9.21-3.27 logarithmic units. L interacts with Cu2+ and Zn2+ forming in both cases, neutral, protonated, and hydroxylated mono- and binuclear complexes whose constants have been calculated by potentiometry in 0.15 M NaClO4 at 298.1 K. The crystal structures of the compounds [Cu(HL-carb)(H2O)](ClO4)3.2H2O (1) and [Cu2(H2L)(CO3)]2(ClO4)8.9H2O (2) have been solved by X-ray diffraction. In 1, the metal center presents square pyramidal geometry. The base …

Effect of Nitrogen Methylation on Cation and Anion Coordination by Hexa- and Heptaazamacrocycles. Catalytic Properties of These Ligands in ATP Dephosphorylation

The stability constants of the complexes formed by 1,10-dimethyl-1,4,7,10,13,16-hexaazacyclooctadecane (L) and 1,4,7-trimethyl-1,4,7,10,13,16,19-heptaazacyclohenicosane (L1) with Ni(2+), Cu(2+), Zn(2+), Cd(2+), and Pb(2+), as well as that for the formation of PbL2(2+) (L2 = 1,4,7,13-tetramethyl-1,4,7,10,13,16-hexaazacyclooctadecane), were determined by means of potentiometric (pH-metric) titrations in 0.15 mol dm(-)(3) NaClO(4) at 298.1 +/- 0.1 K. The enthalpy changes for the formation of Cu(2+) complexes with L and L1 were measured by means of microcalorimetry. These thermodynamic data were compared with those previously reported for L2, 1,4,7,10,13,16-hexaazacyclooctadecane (L3), and 1,4,…

Synthesis and photophysical properties of dansyl-based polyamine ligands and their Zn(II) complexes

The synthesis, potentiometric studies and photophysical properties of two new polyamine ligands (L1 and L2) possessing the dansyl chromophore were studied in aqueous 0.15 M NaCl. The compounds show the absorption and emissions bands characteristic of the dansylamide fluorophore and both present intramolecular excited state proton transfer at intermediate pH ranges. One of the ligands (L2) strongly coordinates Zn(II) leading to fluorescence quenching. A model compound (L3) of the dansyl moiety was also investigated. http://www.sciencedirect.com/science/article/B6TG5-4MB4DV1-2/1/45cafbcee9a8df7daddd765512437ca3

Properties of a triazolopyridine system as a molecular chemosensor for metal ions, anions, and amino acids.

The characteristics as a chemosensor of the compound 3-methyl-6,8-di(2-pyridyl)-[1,2,3]triazolo[5',1':6,1]pyrido[2,3-]pyrimidine (1) have been analyzed. Interaction with Cu(2+) produces a quenching of the fluorescence, while interaction with Zn(2+) leads to a quenching of the fluorescence followed by a bathochromic shift. The crystal structure of the Zn(1)(H(2)O)(3)(ClO(4))(2) x H(2)O complex shows the coordination of Zn(2+) through the terpyridine moiety. The octahedral site is completed by three water molecules. Interactions of the Zn(2+) complex with the anions sulfate, nitrate, nitrite, and dihydrogenphosphate in ethanol produce hypsochromic shifts and restoration of the fluorescence wh…

Cu2+-Induced formation of cage-like compounds containing pyrazole macrocycles

The crystal structure of the complex [Cu4(H22L)2(H2O)2- (ClO4)2](ClO4)2·2H2O where L is a new pyrazole ligand containing 1,5-diaminopentane spacers represents a new form of obtaining metal ion-induced inorganic–organic cages. Escarti Alemany, Francisco, franesa@alumni.uv.es ; Latorre Saborit, Julio, Julio.Latorre@uv.es ; Garcia-España Monsonis, Enrique, Enrique.Garcia-Es@uv.es

Solution and solid state studies with the bis-oxalato building block [Cr(pyim)(C2O4)2]− [pyim = 2-(2′-pyridyl)imidazole]

The preparation, X-ray structure, and variable temperature magnetic study of the new compound {Ba(H2O)3/2[Cr(pyim)(C2O4)2]2}n·9/2nH2O (1) [pyim = 2-(2′-pyridyl)imidazole and C2O42− = dianion of oxalic acid], together with the potentiometric and spectrophotometric studies of the protonation/deprotonation equilibria of the pyim ligand and the ternary complex [Cr(pyim)(C2O4)2]−, are reported herein. The crystal structure of 1 consists of neutral chains, with diamond-shaped units sharing barium(II), with the two other corners occupied by chromium(III). The two metal centers are connected through bis(bidentate) oxalate. Very weak antiferromagnetic interactions between the chromium(III) ions occu…

MWCNTs-Supported Pd(II) Complexes with High Catalytic Efficiency in Oxygen Reduction Reaction in Alkaline Media

We report here the remarkable catalytic efficiency observed for two Pd(II) azamacrocyclic complexes supported on multiwalled carbon nanotubes (MWCNTs) toward oxygen reduction reactions. Beyond a main (90%) 4e

Surface-Enhanced Raman Study of the Interactions between Tripodal Cationic Polyamines and Polynucleotides

Raman and surface-enhanced Raman spectra of new DNA/RNA-binding compounds consisting of three imidazole (Im) and three pyridine (Py) rings connected by tripodal polyaminomethylene linkages were obtained by the near-infrared excitation at 1064 nm. Study of interactions of Im and Py polyamines with single-stranded RNA polynucleotides (poly A, poly G, poly C, poly U), double-stranded DNA polynucleotides (poly dAdT-poly dAdT, poly dGdC-poly dGdC) and calf thymus DNA (ct-DNA) by surface-enhanced Raman spectroscopy (SERS) reveals unambiguous enhancement of the Raman scattering from the small molecules as well as appearance of new bands in spectra associated mainly with nucleobases. The SERS exper…

Switching from intramolecular energy transfer to intramolecular electron transfer by the action of pH and Zn2+ co-ordination

http://www.sciencedirect.com/science/article/B6TFN-44SKJK4-4/1/7cd5958d3acd1757d2b3a88517f1d557

A thermodynamic insight into the recognition of hydrophilic and hydrophobic amino acids in pure water by aza-scorpiand type receptors.

Interactions of different hydrophilic (His, Asp, Glu,) and hydrophobic (Ala, Phe, Tyr, Trp) amino acids in water with a scorpiand aza-macrocycle (L1) containing a pyridine group in the ring and its derivative (L2) bearing a naphthalene group in the tail have been analysed by potentiometric and calorimetric measurements. Theoretical calculations corroborate that major attractive forces that hold the adduct together are hydrogen bonds and salt-bridges, even though other interactions such as π-stacking or NH(+)⋯π may contribute in the case of hydrophobic amino acids and L2. Calorimetric measurements indicate that the interactions between L1 and the different amino acids are principally driven …

Hydrogen-ion driven molecular motions in Cu2+-complexes of a ditopic phenanthrolinophane ligand

One of the first kinetic evaluations of a metal ion interchange between the two coordination sites of a ditopic macrocycle is presented. Garcia-España Monsonis, Enrique, Enrique.Garcia-Es@uv.es ; Soriano Soto, Concepción, Concepcion.Soriano@uv.es ; Verdejo Viu, Begoña, Begona.Verdejo@uv.es

Fluorescent Type II Materials from Naphthylmethyl Polyamine Precursors

Speciation studies in aqueous solution on the interaction of Cu2+ and Zn2+ with a series of polyaminic ligands N-naphthalen-1-ylmethyl-N′-{2-[(naphthalen-1-ylmethyl)-amino]-ethyl}-ethane-1,2-diamine (Ll), N-naphthalen-1-ylmethyl-N′-(2-{2-[(naphthalen-1-ylmethyl)-amino]-ethylamino}-ethyl)-ethane-1,2-diamine (L2) and N-naphthalen-1-ylmethyl-N′-[2-(2-{2-[(naphthalen-1-ylmethyl)-amino]-ethylamino}-ethylamino)-ethyl]-ethane-1,2-diamine (L3) containing two naphthylmethyl groups at their termini and N 1-(2-{2-[(naphthalen-1-ylmethyl)-amino]-ethylamino}-ethyl)-ethane-1,2-diamine (L4) containing just one naphthylmethyl group have been carried out at 298.1 K in 0.15 mol dm−3 NaCl. In the case of the …

Zn(II)-coordination and fluorescence studies of a new polyazamacrocycle incorporating 1H-pyrazole and naphthalene units.

The synthesis and Zn(2+) coordination properties of a new macrocycle (L1) obtained by dipodal (2 + 2) condensation of the polyamine 3-(naphthalen-2-ylmethyl)pentane-1,5-diamine with 1H-pyrazole-3,5-dicarbaldehyde are reported. pH-metric studies show that L1 bears five measurable protonation steps in the 2.0-11.0 pH range. Fluorescence emission studies indicate that the removal of the first proton from the H(5)L1(5+) species leads to a significant decrease in the emission due to a photoinduced electron transfer process. Addition of Zn(2+) promotes a boat-like conformation that approaches both fluorophores and facilitates the formation of an excimer which reaches its highest emission for a 1 …

Azacoronands and Azacyclophanes

Azacycloalkanes and azacyclophanes are among the first macrocyclic ligands developed in the field of supramolecular chemistry. Since they are polyamines, they show dual nature in the coordination of both metal cations, when they are in the free-base form, and anionic species, when they are protonated. As a matter of fact, they played a key role in the birth of macrocyclic chemistry of transition metal complexes and anion coordination chemistry. Furthermore, azacyclophanes fostered also the birth of apolar complexation in aqueous solution, since their aromatic units act as binding sites for apolar substrates. Keywords: azacycloalkanes; azacyclophanes; metal complexes; anion complexes; apolar…

Spectroscopic and DFT Characterization of a Highly Reactive Nonheme FeV–Oxo Intermediate

The reaction of [(PyNMe3)FeII(CF3SO3)2], 1, with excess peracetic acid at −40 °C generates a highly reactive intermediate, 2b(PAA), that has the fastest rate to date for oxidizing cyclohexane by a nonheme iron species. It exhibits an intense 490 nm chromophore associated with an S = 1/2 EPR signal having g-values at 2.07, 2.01, and 1.94. This species was shown to be in a fast equilibrium with a second S = 1/2 species, 2a(PAA), assigned to a low-spin acylperoxoiron(III) center. Unfortunately, contaminants accompanying the 2(PAA) samples prevented determination of the iron oxidation state by Mossbauer spectroscopy. Use of MeO-PyNMe3 (an electron-enriched version of PyNMe3) and cyclohexyl pero…

Anion coordination chemistry in aqueous solution of polyammonium receptors

The behavior of polyamines as receptors of selected families of anions in water is explored. First metallocyanide interaction with saturated polyammonium hosts is analyzed both in solution and in the solid state. The utility of potentiometry, multinuclear NMR, microcalorimetry and cyclic voltammetry to describe solution features of this chemistry is described for selected systems. Sulfate, phosphate, polyphosphate and nucleotide interactions with large polyammonium receptors are then reviewed. Hydrogen bond formation is discussed from a thermodynamic point of view. The influence of the presence of aromatic fragments within the structure on the binding strength is discussed. Factors affectin…

Molecular Switching, Logics, and Memories

The concepts of molecular switch, molecular logics and memories are intimately related. In this work a review of these three topics is given. While the main examples concern the field of inorganic chemistry, in a few cases organic systems are presented to better illustrate the concepts. The basic notions of the logics gates usually used by the nowadays computers is presented and the modus operandi to transpose these concepts to the molecular level is discussed. Examples of switches driven by external stimuli such as light-induced, metal-ion, redox, photobistable, and complexation–decomplexation are described in this chapter. The extension of switches working in solution to solid devices are…

Spectroscopy and Coordination Chemistry of a New Bisnaphthalene−Bisphenanthroline Ligand Displaying a Sensing Ability for Metal Cations

A new fluorescent macrocyclic structure (L1) bearing two naphthalene units at both ends of a cyclic polyaminic chain containing two phenanthroline units was investigated with potentiometric and fluorescence (steady-state and time-resolved) techniques. The fluorescence emission spectra show the simultaneous presence of three bands: a short wavelength emission band (naphthalene monomer), a middle emission band (phenanthroline emission), and a long-wavelength band. All three bands were found to be dependent on the protonation state of the macrocyclic unit (including the polyaminic and phenanthroline structures). The existence of the long-wavelength emission band is discussed and is shown to im…

A highly enantioselective abiotic receptor for malate dianion in aqueous solution

The highly enantioselective molecular recognition of the malate dianion by a synthetic receptor in aqueous solution has been studied by potentiometric titrations, mass spectrometry (ESI-MS), diffusion measurements (PGSE NMR) and molecular modeling. Garcia-España Monsonis, Enrique, Enrique.Garcia-Es@uv.es

ChemInform Abstract: Supramolecular Complexation for Environmental Control

Supramolecular complexes offer a new and efficient way for the monitoring and removal of many substances emanating from technical processes, fertilization, plant and animal protection, or e.g. chemotherapy. Such pollutants range from toxic or radioactive metal ions and anions to chemical side products, herbicides, pesticides to drugs including steroids, and include degradation products from natural sources. The applications involve usually fast and reversible complex formation, due to prevailing non-covalent interactions. This is of importance for sensing as well as for separation techniques, where the often expensive host compounds can then be reused almost indefinitely. Immobilization of …

Chemosensors displaying pH controlled multistage fluorescence emission

A large number of systems displaying pH controlled multistages of fluorescence emission intensity, have not been recognized from this point of view. In this work we present two paradigmatic cases: (i) polyamine receptors linked to a fluorophore unit, in which the signal is modulated by an intra-molecular pH dependent electron transfer process, (ii) phenols presenting adiabatic excited state proton transfer. In the first example the chemosensors are constituted by a receptor unit containing a polyaza moiety suitable for binding protons (but also metal ions or anions). The receptor is linked to a benzene or naphthalene unit that acts as a fluorophore. The fluorescence signal is dependent on t…

Selective encapsulation of a chloride anion in a 1H-pyrazole Cu2+ metallocage

A self-assembled metallobox from copper(ii) and two macrocycles containing 1H-pyrazole ligands has been prepared. The internal cavity of the box is able to selectively encapsulate a single chloride anion over any other halide anion.

Potentiometric, NMR, and Fluorescence-Emission Studies on the Binding of Adenosine 5′-Triphosphate (ATP) by Open-Chain Polyamine Receptors Containing Naphthylmethyl and/or Anthrylmethyl Groups

The interaction in aqueous solution of adenosine 5′-triphosphate (ATP) with a series of open-chain polyamines linked at one or both ends to anthrylmethyl or naphthylmethyl fragments was followed by potentiometric titration, 1H-, 13C-, and 31P-NMR spectroscopy, and by steady-state fluorescence measurements. The results revealed greater stabilities for the compounds containing one anthracene moiety than for those with one naphthalene moiety, the stabilities of the compounds with both ends N-substituted with naphthylmethyl groups being close to those containing just one anthrylmethyl unit. The 1H-NMR spectra showed that in all systems, there is involvement of π-π stacking interactions in the s…

Simple dialkyl pyrazole-3,5-dicarboxylates show in vitro and in vivo activity against disease-causing trypanosomatids.

SUMMARYThe synthesis and antiprotozoal activity of some simple dialkyl pyrazole-3,5-dicarboxylates (compounds 2–6) and their sodium salts (pyrazolates) (compounds 7–9) against Trypanosoma cruzi, Leishmania infantum and Leishmania braziliensis are reported. In most cases the studied compounds showed, especially against the clinically significant amastigote forms, in vitro activities higher than those of the reference drugs (benznidazole for T. cruzi and glucantime for Leishmania spp.); furthermore, the low non-specific cytotoxicities against Vero cells and macrophages shown by these compounds led to good selectivity indexes, which are 8–72 times higher for T. cruzi amastigotes and 15–113 tim…

CO2 Fixation by Copper(II) Complexes of a Terpyridinophane Aza Receptor

CO2 is fixed by a Cu2+ complex of a macrocyclic terpyridinophane ligand forming a carbamate group. Several features of the structure mimic the enzyme rubisco.

Synthesis, Protonation and Cu II Complexes of Two Novel Isomeric Pentaazacyclophane Ligands: Potentiometric, DFT, Kinetic and AMP Recognition Studies

The synthesis and coordination chemistry of two novel ligands, 2,6,9,12,16-pentaaza[17]metacyclophane (L1) and 2,6,9,12,16-pentaaza[17]paracyclophane (L2), is described. Potentiometric studies indicate that L1 and L2 form a variety of mononuclear complexes the stability constants of which reveal a change in the denticity of the ligand when moving from L1 to L2, a behaviour that can be qualitatively explained by the inability of the paracyclophanes to simultaneously use both benzylic nitrogen atoms for coordination to a single metal centre. In contrast, the formation of dinuclear hydroxylated complexes is more favoured for the paraL2 ligand. DFT calculations have been carried out to compare …

Highlights of metal ion-based photochemical switches

Abstract Selected metal complexes behaving as photochemical switches, mostly operating by light emission/absorption without the intervention of any added chemical species, are reviewed. First, the switching mechanisms are analyzed to offer readers an easier understanding of the described systems. Examples of photochemical switching based on complexation/decomplexation processes and photo-bistable systems, comprising metal complexes with azobenzene, azopyridine, diarylethene, spirocyclic and rhodamine ligands, make the central body of the review. These examples were chosen to provide an overview of the evolution of metal-ion based photochemical switches, collecting together historical cases …

Combining Amines and 3-(2-Pyridyl)-[1,2,3]Triazolo[1,5-a]pyridine: An Easy Access to New Functional Polynitrogenated Ligands

Triazolopyridine-pyridine amine ligands are easily obtained by means of either thermal- or copper(II)-mediated reactions. Starting from a readily accessible iodo derivative of triazolopyridine-pyridine and different amines, this new family of compounds combines aromatic and aliphatic nitrogen atoms with promising coordinating properties. Furthermore, chemical derivatization of a new triazolopyridine-pyridine diamine compound, N1-[6-([1,2,3]triazolo[1,5-a]pyridin-3-yl)pyridin-2-yl]ethan-1,2-diamine, allows the preparation of several remote-pyridine-containing ligands.

Coordination of Cu2+ Ions to C2 Symmetric Pseudopeptides Derived from Valine

The acid-base and coordination properties of a family of pseudopeptidic ligands with C(2) symmetry derived from valine (4a-e) have been studied using a variety of techniques as a model for metal coordination in peptides and proteins. The Cu(2+) cation has been selected for coordination studies, although, for comparison, some results for Zn(2+) are also presented. Good agreement has been obtained between the results obtained by potentiometric titrations, spectroscopic analysis, and mass spectrometry (ESI) studies. These results highlight the potential for the use of ESI MS for characterizing the nature of the complex species formed. Clearly, the Cu(2+) complexes are much more stable than the…

Unveiling the reaction mechanism of novel copper N-alkylated tetra-azacyclophanes with outstanding superoxide dismutase activity.

Quantum chemical and multiscale calculations reveal the mechanistic pathway of two superoxide dismutase mimetic N-alkylated tetra-azacyclophane copper complexes with remarkable activity. The arrangement of the binding site afforded by the bulky alkyl substituents and the coordinated water molecule as a proton source play key roles in the reaction mechanism.

Dicopper(II) Metallacyclophanes with N,N'-2,6-Pyridinebis(oxamate): Solution Study, Synthesis, Crystal Structures, and Magnetic Properties.

The complexing ability of copper(II) in solution by the ligand N,N'-2,6-pyridinebis(oxamic acid) (H4mpyba, H4L) was determined through potentiometric and UV-vis spectroscopy at 25 °C and 0.15 M NaCl. The logarithms of the equilibrium constants for its copper(II) complexes according to the eqs 2H2L + 2Cu ⇆ [Cu2(H2L)2], 2H2L + 2Cu ⇆ [Cu2(H2L) (HL)] + H, 2H2L + 2Cu ⇆ [Cu2(HL)2] + 2H, 2H2L + 2Cu ⇆ [Cu2(HL)(L)] + 3H, and 2H2L + 2Cu ⇆ [Cu2L2] + 4H were 12.02(7), 8.04(5), 1.26(6), -7.51(6), and -16.36(6), respectively. The knowledge of the solution behavior has supported the synthesis of three new compounds bearing the common building block Cu2L2(4-). Their formulas are (Me4N)4[Cu2(mpyba)2(H2O)2]·…

Zn2+ and Cu2+ complexes of a fluorescent scorpiand-type oxadiazole azamacrocyclic ligand: crystal structures, solution studies and optical properties

A ligand comprised of a macrocyclic pyridinophane core having a pendant arm containing a secondary amine group linked through a methylene spacer to a pyridyl–oxadiazole–phenyl (PyPD) fluorescent system has been prepared (L). The crystal structures of [ZnL](ClO4)2 and [CuL](ClO4)2 show that M2+ is coordinated to all the nitrogen atoms of the macrocyclic core, the secondary amine of the pendant arm and the nitrogen atom of the pyridine group of the fluorescent moiety, the latter bond being clearly weaker than the one with the pyridine of the macrocycle. Solution studies showed the formation of a highly stable Cu2+ complex with 1 : 1 stoichiometry, whereas with Zn2+ least stable complexes were…

Kinetic study of the oxidation of [Fe(CN)6]4− by [Co(NH3)4pzCO2]2+ and S2O82- in the presence of the tripodal ligand Tren Aminopropil

Abstract Oxidations (electron transfers) of [Fe(CN)6]4− by [Co(NH3)4pzCO2]2+ and S 2 O 8 2 - have been studied in solutions containing the receptor N,N′,N″-(aminopropil)-tris (2-aminoetil) amina [Tren Aminopropil, TAL], which can incorporate [Fe(CN)6]4− and S 2 O 8 2 - but not the cobalt complex. The results can be explained using the Bronsted equation that allows to obtain the binding constant of the transition state, a parameter that the Pseudophase Model cannot provide.

Inhibitory Effect of Azamacrocyclic Ligands on Polyphenol Oxidase in Model and Food Systems

[EN] Enzymatic browning is one of the main problems faced by the food industry due to the enzyme polyphenol oxidase (PPO) provoking an undesirable color change in the presence of oxygen. Here, we report the evaluation of 10 different azamacrocyclic compounds with diverse morphologies as potential inhibitors against the activity of PPO, both in model and real systems. An initial screening of 10 ligands shows that all azamacrocyclic compounds inhibit to some extent the enzymatic browning, but the molecular structure plays a crucial role on the power of inhibition. Kinetic studies of the most active ligand (L2) reveal a S-parabolic I-parabolic noncompetitive inhibition mechanism and a remarkab…

Nanoparticles as Contrast Agents for MRI of Atherosclerotic Lesions

Nanoparticle contrast agents for MRI may aid in identifying atherosclerotic lesions that give rise to ischemic events by means of penetration and retention in the plaque. These imaging agents may provide valuable information regarding plaque characteristics which can help determine the risk of plaque rupture. By increasing molecular flexibility or adding a means of specifically targeting ligands via antibody or peptide, nanoparticles can enhance certain regions of the atherosclerotic plaque. The development of single contrast agents detectable with multiple imaging modalities may further improve our ability to detect and characterize atherosclerosis in clinical and preclinical applications.…

Equilibrium, Kinetic, and Computational Studies on the Formation of Cu2+ and Zn2+ Complexes with an Indazole-Containing Azamacrocyclic Scorpiand: Evidence for Metal-Induced Tautomerism

Cu(2+) and Zn(2+) coordination chemistry of a new member of the family of scorpiand-like macrocyclic ligands derived from tris(2-aminoethyl)amine (tren) is reported. The new ligand (L1) contains in its pendant arm not only the amine group derived from tren but also a 6-indazole ring. Potentiometric studies allow the determination of four protonation constants. UV-vis and fluorescence data support that the last protonation step occurs on the indazole group. Equilibrium measurements in the presence of Cu(2+) and Zn(2+) reveal the formation of stable [ML1](2+), [MHL1](3+), and [ML1(OH)](+) complexes. Kinetic studies on the acid-promoted decomposition of the metal complexes were carried out usi…

Tritopic phenanthroline and pyridine tail-tied aza-scorpiands

The synthesis of two new tritopic double-scorpiand receptors in which two equivalent 5-(2-aminoethyl)-2,5,8-triaza[9]-(2,6)-pyridinophane moieties have been linked with 2,6-dimethylpyridine (L1) or 2,9-dimethylphenanthroline (L2) units is reported for the first time. Their acid-base behaviour and Zn(2+) coordination chemistry have been studied by pH-metric titrations, molecular dynamic calculations, NMR, UV-Vis and steady-state fluorescence techniques. L1 and L2 behave, respectively, as hexaprotic and heptaprotic bases in the experimental conditions used (298.1 +/- 0.1 K, 0.15 mol dm(-3) NaCl, pH range under study 2.0-11.0). These ligands are able to form mono-, bi- and trinuclear Zn(2+) co…

Hydrophobic effects in the stabilisation of copper(I) by the macrocyclic ligands 16,17,19,20-tetramethyl-2,6,9,13-tetraaza[14]paracyclophane and 14,15,17,18-tetramethyl-2,5,8,11-tetraaza[12]paracyclophane

Abstract The interaction of Cu 2+ with the para -azacychlophanes 16,17,19,20-tetramethyl-2,6,9,13-tetraazal[14]paracyclophane (L1) and 14,15,17,18-tetramethyl-2,5,8,11-tetraaza[12]paracyclophane (L2) has been studied by potentiometry, and direct microcalorimetry at 298.1±0.1 K in 0.15 mol dm −3 NaClO 4 . The stability constants (log K CuLi = 13.35(3), log K CuL2 = 9.32(4)) and the thermodynamic parameters ( ΔH ° CuL1 = −47.3(8) kJ mol −1 , ΔH ° CuL2 = 20.9(8) kJ mol −1 ) evidence that not all four nitrogen atoms in the ligands are involved in the coordination to the metal centre. These results, particulary in the case of L1, are similar to those reported for the analogous cyclophanes contai…

Structural characterization in solution of multifunctional nucleotide coordination systems

The interaction in aqueous solution of the cyclophane receptors 2,6,10,13,17,21-hexaaza[22]orthocyclophane (L11) and 2,6,10,13,17,21-hexaaza[22]paracyclophane (L22) with the nucleotides ATP, ADP and AMP has been studied by pH titration and NMR. The obtained results are compared with those previously reported for the analogous meta-substituted receptor 2,6,10,13,17,21-hexaaza[22]metacyclophane (L). All the experimental data support the actuation of these cyclophane molecules as multi-point binders of nucleotides through electrostatic, hydrogen bonding and π-stacking interactions. The combined use of NMR and molecular dynamics permits us to get a rather reliable picture of the way in which th…

Cascade complex formation by phosphate in the cobalt(II)/[30]aneN10 anaerobic system

Abstract The interaction of phosphate with the mono- and binuclear cobalt(II) complexes of [30]aneN 10 (1,4,7,10,13,16,19,22,25,28-decaazacyclotriacontane) has been studied by potentiometry in 0.15 mol dm −3 NaClO 4 solution at 298.15 K under anaerobic conditions. The stable species [CoH 2 ([30]aneN 10 )PO 4 ] + , [CoH 4 ([30]aneN 10 )PO 4 ] 3+ , [Co 2 H([30]aneN 10 )PO 4 ] 2+ , [Co 2 H 2 ([30]aneN 10 )PO 4 ] 3+ and [Co 2 H 3 ([30]aneN 10 )PO 4 ] 4+ , where the phosphate anion is directly bound to the metal ions or acts as a second sphere ligand, are formed and their stability constants have been determined. The results obtained allowed for the selection of suitable conditions for the study…

A New Heterogeneous Catalyst Obtained via Supramolecular Decoration of Graphene with a Pd2+ Azamacrocyclic Complex

A new G-(H2L)-Pd heterogeneous catalyst has been prepared via a self-assembly process consisting in the spontaneous adsorption, in water at room temperature, of a macrocyclic H2L ligand on graphene (G) (G + H2L = G-(H2L)), followed by decoration of the macrocycle with Pd2+ ions (G-(H2L) + Pd2+ = G-(H2L)-Pd) under the same mild conditions. This supramolecular approach is a sustainable (green) procedure that preserves the special characteristics of graphene and furnishes an efficient catalyst for the Cu-free Sonogashira cross coupling reaction between iodobenzene and phenylacetylene. Indeed, G-(H2L)-Pd shows an excellent conversion (90%) of reactants into diphenylacetylene under mild conditio…

1,4,8,11-Tetrakis(4-ferrocenyl-3-azabutyl)-1,4,8,11-tetraazacyclotetradecane as a ferrocene-functionalised polyammonium receptor for electrochemical anion sensing

The interaction of the ferrocene-functionalised polyaza receptor 1,4,8,11-tetrakis(4-ferrocenyl-3-azabutyl)-1,4,8,11-tetraazacyclotetradecane (L1) with sulfate, phosphate and ATP has been studied potentiometrically in THF–water 70∶30 v/v (0.1 mol dm–3 tetrabutylammonium perchlorate, 25 °C). The molecular structure of the free receptor has been determined by single-crystal X-ray procedures. An electrochemical study on L1 as a function of the pH has been carried out in THF–water 70∶30 v/v in the presence of the sulfate, phosphate and ATP anions. The potential use of L1 as an anion sensing receptor is discussed in terms of the electrochemical and potentiometric data and its behaviour is compar…

From isolated 1H-pyrazole cryptand anion receptors to hybrid inorganic-organic 1D helical polymeric anion receptors

We report a novel 1-D helical coordination polymer formed by protonated polyamine 1H-pyrazole cryptands interconnected by Cu2+ metal ions that are able to encapsulate anionic species behaving as a multianion receptor. Switching from a monomeric receptor to a polymeric receptor is activated by metal ions and pH.

Aza-macrocyclic triphenylamine ligands for G-quadruplex recognition

A new series of triphenylamine-based ligands with one (TPA1PY), two (TPA2PY) or three pendant aza-macrocycle(s) (TPA3PY) has been synthesised and studied by means of pH-metric titrations, UV/Vis spectroscopy and fluorescence experiments. The affinity of these ligands for G-quadruplex (G4) DNA and the selectivity they show for G4s over duplex DNA were investigated by Forster resonance energy transfer (FRET) melting assays, fluorimetric titrations and circular dichroism spectroscopy. Interestingly, the interactions of the bi- and especially the tri-branched ligands with G4s lead to a very intense redshifted fluorescence emission band that may be associated with intermolecular aggregation betw…

Dual role of silver in a fluorogenic N-squaraine probe based on Ag(i)–π interactions

In the presence of Ag(I), the monoanion of cyano-N-squaraine (I) generates an intense fluorescence turn-on response. Experimental evidence and DFT calculations reveal a sequence of deprotonation-coordination events in which the Ag(I) ions play a dual role as a Lewis acid and coordinating metal. The observed effect is highly selective for Ag(I) compared to other metals.

Interaction of Zn(II) and Cd(II) with Large Polyazacycloalkanes in dmso/H2O (80:20 vol./vol.). A potentiometric Study.

Abstract A potentiometric study on the interaction at 25 °C and 0.15 mol dm −3 between large polyazacycloalkanes of the series [3 k ]aneN k and Zn(II) and Cd(II) ions in dmso:H 2 O (80:20 vol./vol.) is reported. The protonation behavior of the free macrocycles and coordination trends are compared with those previously observed in aqueous solution. The main features observed in the mixed solvent are: similar protonation behavior of the free polyamines, greater tendency to form binuclear and protonated complexes and a lower tendency to bear hydrolytic reactions.

Specific and highly efficient condensation of GC and IC DNA by polyaza pyridinophane derivatives

Abstract Two bis-polyaza pyridinophane derivatives and their monomeric reference compounds revealed strong interactions with ds-DNA and RNA. The bis-derivatives show a specific condensation of GC- and IC-DNA, which is almost two orders of magnitude more efficient than the well-known condensation agent spermine. The type of condensed DNA was identified as ψ-DNA, characterized by the exceptionally strong CD signals. At variance to the almost silent AT(U) polynucleotides, these strong CD signals allow the determination of GC-condensates at nanomolar nucleobase concentrations. Detailed thermodynamic characterisation by ITC reveals significant differences between the DNA binding of the bis-deriv…

Oxidative stress protection by manganese complexes of tail-tied aza-scorpiand ligands.

The Mn2+ coordination chemistry of double scorpiand ligands in which two polyazacyclophane macrocycles have been connected by pyridine, phenanthroline and bipyridine spacers has been studied by potentiometry, paramagnetic NMR and electrochemistry. All ligands show high stability with Mn2+ and the complexes were formed in a wide pH range. DFT calculations support the structures and coordination geometries derived from the study. A remarkable antioxidant activity was evidenced for these systems by the McCord-Fridovich assay and in Escherichiacoli sodAsodB deficient bacterial cells. The three systems were tested as anti-inflammatory drugs in human macrophages measuring the accumulation of cyto…

Assembly of Polyiodide Networks with Cu(II) Complexes of Pyridinol-Based Tetraaza Macrocycles

Polyiodide networks are currently of great practical interest for the preparation of new electronic materials. The participation of metals in the formation of these networks is believed to improve their mechanical performance and thermal stability. Here we report the results on the construction of polyiodide networks obtained using Cu(II) complexes of a series of pyridinol-based tetraazacyclophanes as countercations. The assembly of these crystalline polyiodides takes place from aqueous solutions on the basis of similar structural elements, the [CuL]2+ and [Cu(H–1L)]+ (L = L2, L2-Me, L2-Me3) complex cations, so that the peculiarities induced by the increase of N-methylation of ligands, the …

Isotope fractionation of zinc in the paddy rice soil-water environment and the role of 2’deoxymugineic acid (DMA) as zincophore under Zn limiting conditions

Non-traditional stable isotope systems are increasingly used to study micronutrient cycling and acquisition in terrestrial ecosystems. We previously proposed for zinc (Zn) a conceptual model linking observed isotope signatures and fractionations to biogeochemical processes occurring in the rice soil environment and we suggested that 2’deoxymugineic acid (DMA) could play an important role for rice during the acquisition of Zn when grown under Zn limiting conditions. This proposition was sustained by the extent and direction of isotope fractionation observed during the complexation of Zn with DMA synthesised in our laboratory. Here we report a new set of experimental data from field and labor…

About the relevance of anion-π interactions in water.

Anion-π interactions are emerging as exotic features with potential applications in chemistry. In the last years, their relevance in living systems has been outlined, and so far there is no concluding significant evidence recognized about the participation of anion-π interactions in water because anion-π sensors contain large aromatic hydrophobic surfaces with limited solubility. By transforming a neutral heterocycle (for example quinoline) into its corresponding salt (quinolinium), we have been able to overcome these solubility issues, and new cationic water-soluble fluorophores have been prepared. Herein, we used N-alkylated heterocycles as π-acidic surfaces to shed light on the nature of…

Structural reorganisation in polytopic receptors revealed by kinetic studies.

One of the first kinetic studies of metal ion reorganisation between the different sites of a tritopic polyaza ligand reveals well defined pathways for the movement of the metal ion.

New Insight to the Chemistry of Polyaza[n]paracyclophanes. A 15N NMR Study

Synthesis and coordination properties of an azamacrocyclic Zn(II) chemosensor containing pendent methylnaphthyl groups

The synthesis of a polyazamacrocycle constituted by two diethylenetriamine bridges functionalized at their central nitrogen with naphth-2-ylmethyl units and interconnected through 2,6-dimethylpyridine spacers (L1) is reported. The protonation behaviour of the new macrocycle in water and in water-ethanol 70/30 v/v mixed solvent has been examined by means of pH-metric, UV-Vis and steady-state fluorescence techniques. The fluorescence emission is slightly quenched following the deprotonation of the central tertiary amines and more deeply quenched upon deprotonation of the secondary amino groups. pH-Metric titrations show that in water-ethanol 70/30 v/v L1 forms stable mononuclear complexes wit…

Bicyclo[2.2.2]octane-1,4-dicarboxylic acid: towards transparent metal–organic frameworks

The preparation of transparent porous materials can offer a different access towards the study of molecules under solid confined space. Metal-organic frameworks represent a unique opportunity due to their tunable pore size, however aromatic linkers present strong absorption and reduce the transparency. Herein, we report the first example of a MOF with bicyclic organic dicarboxylic linkers and its use as a solid solvent.

Ground and excited state properties of polyamine chains bearing two terminal naphthalene units

A series of compounds bearing two naphthalene units linked through methylene groups to both ends of different open-chain polyamines has been investigated. The fluorescence emission studies show the presence of an excimer species whose formation depends on the protonation state and length of the polyamine chains and implies the existence of a bending movement in the excited state allowing the two naphthalene units to approach and interact. This interpretation was clearly proven by time-resolved fluorescence with the appearance of double exponential decays with a rise time observed at the excimer emission wavelength. For comparison purposes one bis-chromophoric compound containing a rigid cha…

Enhancement of SOD activity in boehmite supported nanoreceptors

The binuclear Cu2+ complex of a pyridinophane polyamine ligand ranking amongst the fastest SOD mimetics so far reported displays a remarkable SOD activity enhancement when grafted to the surface of boehmite (γ-AlO(OH)) nanoparticles (BNPs).

A Ferromagnetic [Cu3(OH)2]4+Cluster Formed inside a Tritopic Nonaazapyridinophane: Crystal Structure and Solution Studies

Copper(ii) and Zn(ii) coordination chemistry of tetraaza[n]cyclophanes

The acid–base behaviour and Zn2+ and Cu2+ metal coordination chemistry of the novel orthocyclophane ligands 2,5,8,11-tetraaza[12]orthocyclophane (L2) and 2,5,9,12-tetraaza[13]orthocyclophane (L3) and metacyclophane 2,5,8,11-tetraaza[12]metacylophane (L1) are studied. Important differences in the chemistry of these compounds are found depending on the substitution of the aromatic ring. The ortho derivatives are much more basic in their first two protonation steps while the metacyclophane presents much larger constants in the third and fourth protonation stages. The crystal structure of the picrate salt of [H2L3]2+ shows an alternate disposition of the protons in the molecule with formation o…

Thermodynamic study of the interaction of long open-chain polyazaalkanes with cobalt(II) and nickel(II) ions

Complexation equilibria between the open-chain terminally methylated polyamines 1,14-bis(methylamino)-3,6,9,12- tetraazatetradecane (L1), 1,17-bis(methylamino)-3,6,9,12,15-pentaazaheptadecane (L2), 1,20-bis(methylamino)- 3,6,9,12,15,18-hexaazaicosane (L3) and 1,23-bis(methylamino)-3,6,9,12,15,18,21-heptaazatricosane (L4) with Co2+ and Ni2+ have been studied by means of potentiometric and spectrophotometric methods in 0.15 mol dm−3 NaClO4 aqueous solution at 298.15 K The stability constants for the complexes formed have been determined from e.m.f, data. All these ligands form mononuclear ML2+ complexes of similar stability with Co2+ and Ni2+. Binuclear Co2L44+, Ni2L34+ and Ni2L44+ are also f…

Energy transfer between polyamine chains bearing naphthalene terminal units and k3[Co(CN)6]: An example of a molecular photoreactor

Molecular photoreactors consisting of polyamine chains (receptors) bearing terminal naphthalene units (antennae) are described. The receptors are used to bind the substrate hexacyanocobaltate(III) and the antennae to transfer energy to the complex and thus promote a photoaquation reaction.

>3 + 1 = 6 + 2> In Cu(ii) coordination chemistry of 1H-pyrazole aza cryptands

A polyazamacrocycle formed from two tris(2-aminoethyl)amine units connected by 1H-pyrazole units shows unique hexanuclear Cu(ii) complexes by combination of two binuclear Cu(ii) cryptand complexes through pyrazolate moieties belonging to both cryptands. The formation of these dimeric entities has been proven both in solution by potentiometric studies and mass spectroscopy and in the solid state by X-ray diffraction of crystals of three different batches of formulae [Cu6(H-3L)2(H2O)2](TsO)6·22H2O (2), [Cu6(H-3L)2(NO3)2](NO3)4·2H2O (3) and [Cu6(H-3L)2Cl2]Cl4·(C4H5N3O2)2·14.35H2O (4). The hexanuclear unit in 2 and 4 can be viewed like three magnetically independent binuclear complexes with J =…

Kinetics of Zn2+ complexation by a ditopic phenanthroline-azamacrocyclic scorpiand-like receptor.

Coordination of Zn(2+) to a ditopic phenanthroline-macrocycle receptor takes place in three steps, the first one being the coordination to the phenanthroline, followed by the slow movement of the metal to the polyamine macrocycle and a final re-arrangement to coordinate the pendent arm.

Synthesis and cytotoxic activity of a new potential DNA bisintercalator: 1,4-Bis{3-[N-(4-chlorobenzo[g]phthalazin-1-yl)aminopropyl]}piperazine

The synthesis of new 1,4-bisalkylamino (2-4) and 1-alkylamino-4-chloro (5-6) substituted benzo[g]phthalazines is reported. Compounds 2-4 and 6 were prepared both in the free and heteroaromatic ring protonated forms. Bifunctional 6 contains the 1,4-bisaminopropylpiperazine chain as a linker between the two heteroaromatic units, whereas 5 is its monofunctional analogue. The in vitro antitumour activity of the synthesized compounds has been tested against human colon, breast and lung carcinoma cells, and also against human glioblastoma cells. Results obtained show that all of them are active in all cases, but bifunctional 6·2HCl is remarkably effective against the four cell lines tested, exhib…

Geometric Isomerism in Pentacoordinate Cu2+ Complexes: Equilibrium, Kinetic, and Density Functional Theory Studies Reveal the Existence of Equilibrium between Square Pyramidal and Trigonal Bipyramidal Forms for a Tren-Derived Ligand

A ligand (L1) (bis(aminoethyl)[2-(4-quinolylmethyl)aminoethyl]amine) containing a 4-quinolylmethyl group attached to one of the terminal amino groups of tris(2-aminoethyl)amine (tren) has been prepared, and its protonation constants and stability constants for the formation of Cu(2+) complexes have been determined. Kinetic studies on the formation of Cu(2+) complexes in slightly acidic solutions and on the acid-promoted complex decomposition strongly suggest that the Cu(2+)-L1 complex exists in solution as a mixture of two species, one of them showing a trigonal bipyramidal (tbp) coordination environment with an absorption maximum at 890 nm in the electronic spectrum, and the other one bein…

Binding Mode and Selectivity of a Scorpiand-Like Polyamine Ligand to Single- and Double-Stranded DNA and RNA: Metal- and pH-Driven Modulation

The interaction of a polyazacyclophane ligand having an ethylamine pendant arm functionalized with an anthryl group (L), with the single-stranded polynucleotides polyA, polyG, polyU, and polyC as well as with the double-stranded polynucleotides polyA-polyU, poly(dAT)(2), and poly(dGC)(2) has been followed by UV/Vis titration, steady state fluorescence spectroscopy, and thermal denaturation measurements. In the case of the single-stranded polynucleotides, the UV/Vis and fluorescence titrations permit to distinguish between sequences containing purine and pyrimidine bases. For the double-stranded polynucleotides the UV/Vis measurements show for all of them hypochromicity and bathochromic shif…

New strategies in the development of polynuclear complexes. Crystal structure of the tetranuclear copper(II) complex [Cu4(L1)2(OH)4Cl2(H2O)2]2(H3O2)(ClO4)2Cl·2H2O (L1=2,5,8,11-tetraaza[12](1,4)naphthalenecyclophane)

Abstract The preparation and interaction of the new polyaza[n]naphthalenophanes 2,5,8,11-tetraaza[12](1,4)naphthalenophane (L1) and 2,6,9,13-tetraaza[14](1,4)naphthalenophane (L2) with hydrogen ions and Cu2+ is described. The crystal structure of the new tetranuclear copper(II) complex [Cu4(L1)2(OH)4Cl2(H2O)2]2(H3O2)(ClO4)2Cl·2H2O (L1=2,5,8,11-tetraaza[12](1,4)naphthalenophane) is presented and discussed. A variety of intra- and intermolecular forces contribute to the particular organisation of the crystal. The solution studies indicate the formation of similar tetranuclear species for L1 while for L2 just mononuclear 1:1 species are detected.

Small Azaparacyclophanes as Potential Selective Scavengers of Mercury. Crystal Structure of the Complex Hg2(L1)Cl4 (L1 = 16,17,19,20-Tetramethyl-2,6,9,13-tetraaza[14]paracyclophane)

Effective complexation of psychotropic phenethylammonium salts from a disodium dipyrazolate salt of macrocyclic structure

The equilibrium stability constants (Ks) of ammonium pyrazolate complexes [L2−]2RN(R′)H2+ (3, R′ = H and 4, R′ = Me) formed from a macrocyclic disodium dipyrazolate salt 2[L2−] 2Na+ and ammonium salts (RNH3+X− or RN(Me)H2+X−) of psychotropic drugs and neurotransmitter catecholamines have been evaluated by electrochemical methods in DMSO solution. The resulting Ks values demonstrate that, except for (±)-amphetamine, the complexes formed by lipophilic primary [mescaline, (+)-amphetamine, (±)-p-methoxyamphetamine (PMA), (±)-3,4-methylenedioxyamphetamine (MDA)] and secondary [(±)-methamphetamine, (+)-methamphetamine and (±)-3,4-methylenedioxymethamphetamine (MDMA ‘ecstasy’)] phenethylamines are…

CO2fixation and activation by metal complexes of small polyazacyclophanes

The interaction of the cyclophanes 2,6,9,13-tetraaza[14]paracyclophane (L1) and 2,6,9,13-tetraaza[14]metacyclophane (L2) and of their Zn2+ and Cu2+ complexes with CO32− and its protonated forms is described. The actuation of the Cu2+–L2 system as an electrocatalyst for the reduction of CO2 to CO in water is advanced. Copyright © 2001 John Wiley & Sons, Ltd.

Cation and Anion Coordination Chemistry of Palladium(II) with Polyazacycloalkanes. Thermodynamic and Structural Studies

The interaction of PdCI2 4 - with the macrocyclic ligands of the series [3k]aneNk has been studied both in solution and in the solid state. [18]aneN6 and [21]aneN7 form both mono- and binuclear Pd2+ complexes, whose stability constants have been determined in 0.5 mol dm-3 NaCI at 298.15 K. [21]aneN7 also forms, in solution, a trinuclear species in which an amino group deprotonates to bridge two Pd2+ ions, as observed in the solid state. The crystal structure of the complexes [Pd2([18]aneN6)Cl2][CIO4]2 and [Pd3[21]aneN7)CI3][CIO4]2 ⋅ H2O have been solved by single crystal X-ray analysis. C12H30N6CI4O8Pd2: monoclinic, space group C2/m, a = 10.876(2), b = 18.117(2), c = 7.043(2) A, s = 113.78(…

In vitro leishmanicidal activity of pyrazole-containing polyamine macrocycles which inhibit the Fe-SOD enzyme of Leishmania infantum and Leishmania braziliensis species

The in vitro leishmanicidal activity and cytotoxicity of pyrazole-containing macrocyclic polyamines 1-4 was assayed on Leishmania infantum and Leishmania braziliensis species. Compounds 1-4 were more active and less toxic than glucantime and both infection rates and ultrastructural alterations confirmed that 1 and 2 were highly leishmanicidal and induced extensive parasite cell damage. Modifications in the excretion products of parasites treated with 1-3 were also consistent with substantial cytoplasm alterations. Compound 2 was highlighted as a potent inhibitor of Fe-SOD in both species, whereas its effect on human CuZn-SOD was poor. Molecular modelling suggested that 2 could deactivate Fe…

Selective electrochemical discrimination between dopamine and phenethylamine-derived psychotropic drugs using electrodes modified with an acyclic receptor containing two terminal 3-alkoxy-5-nitroindazole rings.

Electrochemical discrimination between dopamine and psychotropic drugs which have in common a skeletal structure of phenethylamine, can be obtained using acyclic receptors L(1) and L(2), containing two terminal 3-alkoxy-5-nitroindazole rings. Upon attachment to graphite electrodes, L(1) and L(2) exhibit a well-defined, essentially reversible solid state electrochemistry in contact with aqueous media, based on electrolyte-assisted reduction processes involving successive cation and anion insertion/binding. As a result, a distinctive, essentially Nernstian electrochemical response is obtained for phenethylammonium ions of methamphetamine (METH), p-methoxyamphetamine (PMA), amphetamine (AMPH),…

In vitro and in vivo antileishmanial and trypanocidal studies of new N-benzene- and N-naphthalenesulfonamide derivatives.

We report in vivo and in vitro antileishmanial and trypanocidal activities of a new series of N-substituted benzene and naphthalenesulfonamides 1-15. Compounds 1-15 were screened in vitro against Leishmania infantum , Leishmania braziliensis , Leishmania guyanensis , Leishmania amazonensis , and Trypanosoma cruzi . Sulfonamides 6e, 10b, and 10d displayed remarkable activity and selectivity toward T. cruzi epimastigotes and amastigotes. 6e showed significant trypanocidal activity on parasitemia in a murine model of acute Chagas disease. Moreover, 6e, 8c, 9c, 12c, and 14d displayed interesting IC50 values against Leishmania spp promastigotes as well as L. amazonensis and L. infantum amastigot…

Construction of green nanostructured heterogeneous catalysts via non-covalent surface decoration of multi-walled carbon nanotubes with Pd(II) complexes of azamacrocycles

Abstract Green nanostructured heterogeneous catalysts were prepared via a bottom-up strategy. Designed ligands were synthesized joining covalently an electrondeficient pyrimidine residue and a scorpiand azamacrocycle. The desired molecular properties were easily transferred to nanostructured materials in two steps: first, exploiting their spontaneous chemisorption onto multi-walled carbon nanotubes (MWCNTs) via the pyrimidinic moiety in water at room temperature, then, taking advantage of the easy coordination of Pd(II) to the azamacrocycle in the same conditions. An evenly distribution of catalytic centres was obtained on the MWCNTs surface. Catalytic properties of these materials were ass…

Manganese(II) complexes of scorpiand-like azamacrocycles as MnSOD mimics.

Mn(II) complexes of scorpiand-type azamacrocycles constituted by a tretrazapyridinophane core appended with an ethylamino tail including 2- or 4-quinoline functionalities show very appealing in vitro SOD activity. The observed behaviour is related to structural and electrochemical parameters.

[1,2,3]Triazolo[1,5-a]pyridine derivatives as molecular chemosensors for zinc(ii), nitrite and cyanide anions

Three recently prepared tridentate ligands TPF, TPS and TPT, based on the triazolopyridine–pyridine nucleus possessing fluorescent properties, have been tested as chemosensors for metal ions. A particular response is obtained in the case of ZnTPT+2. The Zn2+ TPT 1 : 1 complex has proved to be an efficient chemosensor for anions especially nitrite and cyanide.

A New ZnIITweezer Pyridine-Naphthalene System - An Off-On-Off System Working in a Biological pH Window

Their basic idea consisted of the connec-tion of an amine to a fluorophoric anthracene unit on oneside and to a pyridine moiety on the other. At acidic pHvalues the amino and the pyridine groups are protonatedand a photoinduced electron transfer (PET) occurs fromthe π-π* excited state of the anthracene to the protonatedpyridinium unit, leading to quenching of the fluorescence.However, at high pH values, where the amino group is notprotonated, PET alternatively takes place from the aminelone pair to the same excited state of the fluorophore, yield-ing the same inhibitory effect on the fluorescence. Betweenthese two pH values, there is a pH window where PET doesnot take place and fluorescence…

Stability and kinetics of the acid-promoted decomposition of Cu(II) complexes with hexaazacyclophanes: kinetic studies as a probe to detect changes in the coordination mode of the macrocycles.

The synthesis, protonation and Cu(II) coordination features of the novel azacyclophane type receptors 2,6,10,13,17,21-hexaza[22]-(2,6)-pyridinophane (L2), 2,6,9,12,15,19-hexaza[20]-(2,6)-pyridinophane (L5) and 2,6,9,12,15,19-hexaza[20]metacyclophane (L6) are presented. The protonation and Cu(II) constants are analysed and compared with the previously reported open-chain polyamines 4,8,11,15-tetrazaoctadecane-1,18-diamine (L1) and 4,7,10,13-tetraazahexadecane-1,16-diamine (L4) and of the cyclophane 2,6,10,13,17,21-hexaaza[22]paracyclophane (L3). All the systems form mono- and dinuclear complexes whose stability and pH range of existence depend on the type of hydrocarbon chains and molecular …

Stabilisation of Exotic Tribromide (Br3−) Anions via Supramolecular Interaction with A Tosylated Macrocyclic Pyridinophane. A Serendipitous Case.

Tetraaza-macrocyclic pyridinophane L-Ts, decorated with a p-toluenesulfonyl (tosyl

Stabilization of polyiodide networks with Cu(ii) complexes of small methylated polyazacyclophanes: shifting directional control from H-bonds to I⋯I interactions

Ordered polyiodide networks have recently gathered considerable attention as electronic materials, a topic historically dominated by metals. Could we incorporate metal cations into polyiodide frameworks in a controlled manner to simultaneously boost electronic properties and robustness of these materials? Herein we present a first principles study featuring three analogous polyazacyclophanes (L, L-Me, L-Me3), differing only in the extent of N-methylation. We demonstrate (potentiometry, ITC) how they all form the same CuL2+ (L = L, L-Me, L-Me3) complex as prevalent species in solution, so that a level playing field exists where only N-methylation distinguishes them. Then we use them as count…

Cluster dirhenium(III) cis-dicarboxylates with α-amino acids ligands as mighty selective G4s binders.

The synthesis of four dirhenium(III) cis-dicarboxylates with the α-amino acids residues Asp (I), Glu (II), Phe (III) and Tyr (IV) is presented. The G-quadruplex stabilization potential was evaluated by fluorescence resonance energy transfer - melting analysis. All derivatives show specific binding to c-kit1 quadruplex, while II and IV have also strong stabilization activity to HTelo21 quadruplex. At the same time, the compounds do not show any stabilization activity for ds26 DNA, which suggests unique mechanisms of molecular DNA recognition for these complexes.

Polyamines containing naphthyl groups as pH-regulated molecular machines driven by light

A series of compounds made up by linking methylnaphthalene fragments at both ends of different polyamine chains have shown to behave as pH-regulated molecular machines driven by light and fluorescence emission studies have proved the formation of an excimer between the two naphthalene units whose appearance, fluorescence intensity and decay times depend on the pH value of the media. Albelda Gimeno, Maria Teresa, Teresa.Albelda@uv.es ; Garcia-España Monsonis, Enrique, Enrique.Garcia-Es@uv.es ; Soriano Soto, Concepción, Concepcion.Soriano@uv.es

Polyfunctional recognition of pyridinedicarboxylate anions with macrocyclic polyamine receptors containing heteroaromatic groups.

The interaction of the biologically relevant anions deriving from the six pyridinedicarboxylic acids (H2PDC) with two macrocyclic receptors containing a pentamine chain and a bipyridine (1) or a phenanthroline (2) moiety, as well as with the aliphatic analogue [21]aneN7 (3), was studied by means of spectroscopic methods (UV-vis, NMR) and potentiometric titrations affording the stability constants of the adducts formed. All three receptors form stable complexes with the substrates thanks to the formation of several salt bridges and hydrogen bond contacts, as observed in the crystal structure of the H8[3(2,6-PDC)4] x H2O x 0.5 EtOH solid compound. Additional pi-stacking interactions between t…

On the Antibacterial Activity of Azacarboxylate Ligands: Lowered Metal Ion Affinities for Bis-amide Derivatives of EDTA do not mean Reduced Activity.

EDTA is widely used as an inhibitor of bacterial growth, affecting the uptake and control of metal ions by microorganisms. We describe the synthesis and characterisation of two symmetrical bis-amide derivatives of EDTA, featuring glycyl or pyridyl substituents: AmGly2 and AmPy2 . Metal ion affinities (logK) have been evaluated for a range of metals (Mg2+ , Ca2+ , Fe3+ , Mn2+ , Zn2+ ), revealing less avid binding compared to EDTA. The solid-state structures of AmGly2 and of its Mg2+ complex have been determined crystallographically. The latter shows an unusual 7-coordinate, capped octahedral Mg2+ centre. The antibacterial activities of the two ligands and of EDTA have been evaluated against …

Squaramide-based reagent for selective chromogenic sensing of Cu(II) through a zwitterion radical.

A minimalist squaramide-based chemodosimeter for Cu(2+) is described. Upon selective chelation to 2, Cu(2+) induces the formation of a highly colored zwitterionic radical, which is kinetically stable for hours. The presence of a radical is confirmed by EPR and ESI-MS. It is then possible to use reagent 2 for visual and selective sensing of Cu(2+) at neutral pH.

Specific interaction of citrate with bis(fluorophoric) bibrachial lariat aza-crown in comparison with the other components of the Krebs cycle

Clares Garcia, M. Paz, M.Paz.Clares@uv.es ; Garcia-España Monsonis, Enrique, Enrique.Garcia-Es@uv.es ; Soriano Soto, Concepcion, Concepcion.Soriano@uv.es ; Tejero Toquero, Roberto, Roberto.Tejero@uv.es

Copper complexes of polyaza[n]cyclophanes and their interaction with DNA and RNA

Abstract The complexation properties of Cu 2+ ions with the cyclophane receptors 2,6,9,13-tetraaza[14]metacyclophane ( L1 ), 2,6,10,13,17,21-hexaaza[22]metacyclophane ( L2 ) and 2,6,10,13,17,21-hexaaza[22]paracyclophane ( L3 ) are presented. Formation of mononuclear complexes in the case of L1 and of mono- and binuclear complexes in the case of the hexaaazcyclophane ligands L2 and L3 is observed. The coordination numbers around each Cu 2+ in the binuclear complexes involve at most three nitrogen donors for each metal ion. Cyclophanes L1 – L3 and several acyclic polyamine ligands are tested for their affinity towards double-stranded nucleic acid models of RNA and DNA. The binding affinity of…

Imidazolate bridged Cu(II)-Cu(II) and Cu(II)-Zn(II) complexes of a terpyridinophane azamacrocycle: a solution and solid state study.

The dinuclear Cu2+ and Zn2+ as well as the mixed Cu2+-Zn2+ complexes of a 5,5''-pentaazaterpyridinophane ligand (L) are able to incorporate imidazolate (Im-) as a bridging ligand. The crystal structure of [Cu(2)L(Im)(Br)(H2O)](CF(3)SO(3))(2).3H2O (1) shows one copper coordinated by the three pyridine nitrogens of the terpyridine unit, one nitrogen of the imidazolate bridge (Im-) and one bromide anion occupying the axial position of a distorted square pyramid. The second copper atom is coordinated by the remaining imidazolate nitrogen, the three secondary nitrogens at the centre of the polyamine bridge and one water molecule that occupies the axial position. Magnetic measurements have been p…

Hydrogen-bond-mediated self-assembly of 26-membered diaza tetraester crowns of 3,5-disubstituted 1 h -pyrazole. Dimerization study in the solid state and in CDCl3 solution

By using an improved synthetic method reported earlier, the cyclic stannoxanes obtained from RN-diethanolamine (R = Me, Bu) and dibutyltin oxide have been reacted with 1H-pyrazole-3,5-dicarbonyl dichloride to afford 26-membered diaza tetraester crowns (1, R = Me; 3, R = Bu) and 39-membered triaza hexaester crowns (2, R = Me; 4, R = Bu). The new structures were identified from their analytical and spectroscopic (1H and 13C NMR, FAB-MS, and/or ESI-MS) data. Both diaza tetraester crowns (1 and 3), containing two 1H-pyrazole units, self-assemble into dimeric species through the formation of four hydrogen bonds involving the two NH pyrazole groups and the two tertiary amine groups of both crowns…

Molecular recognition of nucleotides in water by scorpiand-type receptors based on nucleobase discrimination.

Abstract: The detection of nucleotides is of crucial impor-tance because they are the basic building blocks of nucleicacids. Scorpiand-based polyamine receptors functionalizedwith pyridine or anthracene units are able to form stablecomplexes with nucleotides in water, based on coulombic,p–p stacking, and hydrogen-bonding interactions. This be-havior has been rationalized by means of an explorationwith NMR spectroscopy and DFT calculations. Binding con-stants were determined by potentiometry. Fluorescencespectroscopy studies have revealed the potential of these re-ceptors as sensors to effectively and selectively distinguishguanosine-5’-triphosphate (GTP) from adenosine-5’-triphos-phate (ATP…

Mechanochemical synthesis of an Eu(III) complex. Preparation and Luminescence Properties of PMMA:[C42H38N5O19Eu] Hybrid Films

Abstract Photoluminescent films of poly(methyl methacrylate), PMMA, doped with the complex [EuL2(H2O)2(NO3)3] were prepared, where L is the neutral ligand 2,6-bis[2-formylphenoxymethyl]pyridine (C21H17NO4). The Eu(III) complex was synthesized by classic chemosynthesis, and also through a solvent-free mechanochemical synthesis, and characterized by spectroscopy, thermal analysis (TGA and DTA), and single crystal X-ray diffraction. The mechanochemical route improves the yield for the complex, which is synthesized over times considerably shorter compared to the traditional synthesis, and through a solvent-free procedure. The photoluminescent properties of the Eu(III) complex and hybrid films P…

ChemInform Abstract: Proton Coordination by Polyamine Compounds in Aqueous Solution

Abstract The present article is concerned with proton transfer reactions in aqueous solution of open-chain, macrocyclic and macropolycyclic or cage compounds having nitrogen atoms as protonation sites in the molecular framework, although several compounds with additional different donors will be considered. The main purpose of this review is to collect some significant examples of proton transfer processes in order to show how the electronic properties and molecular topology of polyamines affect the thermodynamic parameters of their protonation equilibria.

A bibracchial lariat aza-crown ether as an abiotic catalyst of malonic acid enolization

A bibracchial lariat aza-crown ether (L) consisting of 2-aminoethylnaphthyl moieties appended to a 2 : 2 azapyridinophane structure displays significant activation of H–D exchange in malonic acid. The compound forms very stable adducts with malonate anions (MA) in the 2–10 pH range. Molecular dynamics studies performed for the species resulting from the interaction of the hexaprotonated macrocycle and the dianion show that malonate is encapsulated by L with distances between the CH2 group of malonate and the pyridine nitrogens of ca. 3.5 A. The pendant arms of L cap above and below the anion, defining a pseudo-cage structure. Quantum chemical calculations for α-proton abstraction from malon…

Extended structures of copper(II) complexes with 2-di1H-2-imidazolylmethylmalonate (DIMMAL), a versatile bis(imidazole)–bis(carboxylate) ligand: Solution studies, crystal structures and spectroscopic characterization

Abstract Copper(II) complexes of 2-di1H-2-imidazolylmethylmalonate (DIMMAL) have been studied by potentiometric methods. The data revealed that the CuHL 2 - and CuL 2 2 - species are prevalent in the studied pH range. Moreover, this paper reports the synthesis, structure solution and spectroscopic characterization of two new DIMMAL containing complexes, (NH4)2[Cu(DIMMAL)2] · 4H2O (1) and [Cu(DIMMAL)(en)(H2O)] · 5H2O (2). The structure of compound 1 consists of centrosymmetric mononuclear anionic [Cu(DIMMAL)2]2− units, NH 4 + cations and lattice water molecules, in which DIMMAL2− acts as a tridentate ligand through two imidazole nitrogen atoms and one oxygen atom from a carboxylate group. Th…

Hybrid GMP–polyamine hydrogels as new biocompatible materials for drug encapsulation

Here we present the preparation and characterization of new biocompatible materials for drug encapsulation. These new gels are based on positively charged [1+1] 1H-pyrazole-based azamacrocycles which minimise the electrostatic repulsions between the negatively charged GMP molecules. Rheological measurements confirm the electroneutral hydrogel structure as the most stable for all the GMP-polyamine systems. Nuclear magnetic resonance (NMR) was employed to investigate the kinetics of the hydrogel formation and cryo-scanning electron microscopy (cryo-SEM) was used to obtain information about the hydrogel morphology, which exhibited a non-homogeneous structure with a high degree of cross-linking…

A remarkable selectivity in the N-functionalization of polyaza[n]paracyclophanes. Synthesis of N-(4-picolyl)-substituted 2,6,9,13-tetraaza[14]paracyclophanes

Abstract Interaction of cationic host species, in particular Zn 2+ salts, with polyaza[n]paracyclophanes (i.e. 2,6,9,13-Tetraaza[14]paracyclophane, B323 (1a) ) directs their selective N-functionalization. In this way compounds mono- or difunctionalized with ArCH 2− groups at the benzylic nitrogen atoms can be easily obtained. Direct reaction with the alkylating agent, in the absence of the Zn 2+ species, produces, in general, very complex mixtures of mono- and polyalkylated compounds except when 4-picolyl chloride is used. In this case, mono-, di-, tri- and tetra N-substituted derivatives of D323 can be isolated depending on the amount of the alkylating agent used. In this case, the mono- a…

Homo- and Heterobinuclear Cu2+ and Zn2+ Complexes of Ditopic Aza Scorpiand Ligands as Superoxide Dismutase Mimics

Two polytopic aza-scorpiand-like ligands, 6-[7-(diaminoethyl)-3,7-diazaheptyl]-3,6,9-triaza-1-(2,6-pyridina)cyclodecaphane (L1) and 6-[6′-[3,6,9-triaza-1-(2,6-pyridina)cyclodecaphan-6-yl]-3-azahexyl]-3,6,9-triaza-1-(2,6-pyridina)cyclodecaphane (L2), have been synthesized. The acid–base behavior and Cu2+, Zn2+, and Cu2+/Zn2+ mixed coordination have been analyzed by potentiometry, cyclic voltammetry, and UV–vis spectroscopy. The resolution of the crystal structures of [Cu2L2Cl2](ClO4)2·1.67H2O (1), [Cu2HL2Br2](ClO4)3·1.5H2O (2), and [CuZnL2Cl2](ClO4)2·1.64H2O (3) shows, in agreement with the solution data, the formation of homobinuclear Cu2+/Cu2+ and heterobinuclear Cu2+/Zn2+ complexes. The m…

Cu2+and AMP complexation of enlarged tripodal polyamines

The synthesis, characterization, Cu2+ coordination and interaction with AMP of three tripodal polyamines are reported. The polyamines are based on the structure of the tetraamine (tren) which has been enlarged with three propylamino functionalities (TAL), with a further anthrylmethyl fragment at one of its terminal primary nitrogens (ATAL) or with naphthylmethyl fragments at its three ends (N3TAL). The protonation constants of all three polyamines show that at pH 6, all six primary and secondary nitrogen atoms in the arms are protonated. The interaction with Cu2+ and AMP (adenosine-5′-monophosphate) has been studied by potentiometric, UV-Vis, ESI-MS spectroscopy and NMR techniques. pH-Metri…

Oxaaza cyclophanes in the recognition of nucleotides. The role of oxygen and electron-rich aromatic rings

Dioxapolyaza cyclophanes derived from resorcinol and different polyamine chains have been studied in aqueous solution as abiotic receptors for nucleotides. The presence of the additional ethyleneoxy subunits is reflected in a higher basicity and in a significant increase in the log K values for the interaction with nucleotides relative to that of related polyazacyclophanes.

CCDC 1912383: Experimental Crystal Structure Determination

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CCDC 1431346: Experimental Crystal Structure Determination

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CCDC 973978: Experimental Crystal Structure Determination

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CCDC 1964484: Experimental Crystal Structure Determination

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CCDC 1559249: Experimental Crystal Structure Determination

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CCDC 953139: Experimental Crystal Structure Determination

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CCDC 1009322: Experimental Crystal Structure Determination

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CCDC 953539: Experimental Crystal Structure Determination

Related Article: Sandra Gago, Jorge González, Salvador Blasco, A. Jorge Parola, M. T. Albelda, Enrique García-España, Fernando Pina|2014|Dalton Trans.|43|2437|doi:10.1039/C3DT52061G

CCDC 973974: Experimental Crystal Structure Determination

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CCDC 1468808: Experimental Crystal Structure Determination

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CCDC 1559236: Experimental Crystal Structure Determination

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CCDC 1884191: Experimental Crystal Structure Determination

Related Article: Juan C. Frías, José Soriano, Salvador Blasco, Enrique García-España, Aurora Rodríguez-Rodríguez, David Esteban-Gómez, Fabio Carniato, Mauro Botta, Carlos Platas-Iglesias, M. Teresa Albelda|2020|Inorg.Chem.|59|7306|doi:10.1021/acs.inorgchem.0c00690

CCDC 1952561: Experimental Crystal Structure Determination

Related Article: Gianluca Ambrosi, M. Paz Clares, Isabel Pont, Mauro Formica, Vieri Fusi, Angela Ricci, Paola Paoli, Patrizia Rossi, Enrique García-España, Mario Inclán|2020|Dalton Trans.|49|1897|doi:10.1039/C9DT04764F

CCDC 2071315: Experimental Crystal Structure Determination

Related Article: Manel Vega, Salvador Blasco, Enrique García-España, Bartolomé Soberats, Antonio Frontera, Carmen Rotger, Antonio Costa|2021|Dalton Trans.|50|9367|doi:10.1039/D1DT01408K

CCDC 973976: Experimental Crystal Structure Determination

Related Article: Raquel Belda, Javier Pitarch-Jarque, Conxa Soriano, José M. Llinares, Salvador Blasco, Jesús Ferrando-Soria, and Enrique García-España|2013|Inorg.Chem.|52|10795|doi:10.1021/ic400645t

CCDC 1953932: Experimental Crystal Structure Determination

Related Article: Alberto Lopera, Ariadna Gil-Martínez, Javier Pitarch-Jarque, Begoña Verdejo, Salvador Blasco, M. Paz Clares, Hermas R. Jiménez, Enrique García-España|2020|Dalton Trans.|49|8614|doi:10.1039/D0DT01056A

CCDC 1814073: Experimental Crystal Structure Determination

Related Article: Marta Ximenis, Javier Pitarch-Jarque, Salvador Blasco, Carmen Rotger, Enrique García-España, Antonio Costa|2018|Cryst.Growth Des.|18|4420|doi:10.1021/acs.cgd.8b00401

CCDC 1521794: Experimental Crystal Structure Determination

Related Article: M. Paz Clares, Laura Acosta-Rueda, Carmen E. Castillo, Salvador Blasco, Hermas R. Jiménez, Enrique García-España, and Manuel G. Basallote|2017|Inorg.Chem.|56|4400|doi:10.1021/acs.inorgchem.6b03070

CCDC 1009323: Experimental Crystal Structure Determination

Related Article: Laura Acosta-Rueda, Estefanía Delgado-Pinar, Javier Pitarch-Jarque, Alexis Rodríguez, Salvador Blasco, Jorge González, Manuel G. Basallote, Enrique García-España|2015|Dalton Trans.|44|8255|doi:10.1039/C5DT00408J

CCDC 1009325: Experimental Crystal Structure Determination

Related Article: Laura Acosta-Rueda, Estefanía Delgado-Pinar, Javier Pitarch-Jarque, Alexis Rodríguez, Salvador Blasco, Jorge González, Manuel G. Basallote, Enrique García-España|2015|Dalton Trans.|44|8255|doi:10.1039/C5DT00408J

CCDC 1814074: Experimental Crystal Structure Determination

Related Article: Marta Ximenis, Javier Pitarch-Jarque, Salvador Blasco, Carmen Rotger, Enrique García-España, Antonio Costa|2018|Cryst.Growth Des.|18|4420|doi:10.1021/acs.cgd.8b00401

CCDC 892312: Experimental Crystal Structure Determination

Related Article: Javier Pitarch-Jarque, Raquel Belda, Salvador Blasco, Pilar Navarro, Roberto Tejero, José Miguel Junquera-Hernández, Vicente Pérez-Mondéjar, Enrique García-España|2016|New J.Chem.|40|5670|doi:10.1039/C5NJ03234B

CCDC 1827335: Experimental Crystal Structure Determination

Related Article: Álvaro Martínez-Camarena, Andrea Liberato, Estefanía Delgado-Pinar, Andrés G. Algarra, Javier Pitarch-Jarque, José M. Llinares, M. Ángeles Mañez, Antonio Domenech-Carbó, Manuel G. Basallote, Enrique García-España|2018|Inorg.Chem.|57|10961|doi:10.1021/acs.inorgchem.8b01492

CCDC 1982975: Experimental Crystal Structure Determination

Related Article: Álvaro Martínez-Camarena, Pedro A. Sánchez-Murcia, Salvador Blasco, Leticia González, Enrique García-España|2020|Chem.Commun.|56|7511|doi:10.1039/D0CC01926G

CCDC 1020483: Experimental Crystal Structure Determination

Related Article: M. Paz Claresa, Carolina Serena, Salvador Blasco, Aida Nebot, Lucas del Castillo, Conxa Soriano, Antonio Domènech, Ana Virginia Sánchez-Sánchez, Laura Soler-Calero, José Luis Mullor, Antonio García-España, Enrique García-España|2015|J.Inorg.Biochem.|143|1|doi:10.1016/j.jinorgbio.2014.11.001

CCDC 1814075: Experimental Crystal Structure Determination

Related Article: Marta Ximenis, Javier Pitarch-Jarque, Salvador Blasco, Carmen Rotger, Enrique García-España, Antonio Costa|2018|Cryst.Growth Des.|18|4420|doi:10.1021/acs.cgd.8b00401

CCDC 983275: Experimental Crystal Structure Determination

Related Article: Javier Pitarch-Jarque, Raquel Belda, Laura García-España, José M. Llinares, FangFang Pan, Kari Rissanen, Pilar Navarro, Enrique García-España|2015|Dalton Trans.|44|7761|doi:10.1039/C5DT00763A

CCDC 1429442: Experimental Crystal Structure Determination

Related Article: Alexander Ganß, Raquel Belda, Javier Pitarch, Richard Goddard, Enrique García-España, and Stefan Kubik|2015|Org.Lett.|17|5850|doi:10.1021/acs.orglett.5b03027

CCDC 1953930: Experimental Crystal Structure Determination

Related Article: Alberto Lopera, Ariadna Gil-Martínez, Javier Pitarch-Jarque, Begoña Verdejo, Salvador Blasco, M. Paz Clares, Hermas R. Jiménez, Enrique García-España|2020|Dalton Trans.|49|8614|doi:10.1039/D0DT01056A

CCDC 1990725: Experimental Crystal Structure Determination

Related Article: Alberto Lopera, Ariadna Gil-Martínez, Javier Pitarch-Jarque, Begoña Verdejo, Salvador Blasco, M. Paz Clares, Hermas R. Jiménez, Enrique García-España|2020|Dalton Trans.|49|8614|doi:10.1039/D0DT01056A

CCDC 1030676: Experimental Crystal Structure Determination

Related Article: Javier Pitarch-Jarque, Raquel Belda, Laura García-España, José M. Llinares, FangFang Pan, Kari Rissanen, Pilar Navarro, Enrique García-España|2015|Dalton Trans.|44|7761|doi:10.1039/C5DT00763A

CCDC 1507631: Experimental Crystal Structure Determination

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CCDC 946980: Experimental Crystal Structure Determination

Related Article: Francisco R. Fortea-Pérez, Julia Vallejo, Mario Inclán, Mariadel Déniz, Jorge Pasán, Enrique García-España and Miguel Julve|2013|J.Coord.Chem.|66|3349|doi:10.1080/00958972.2013.837460

CCDC 999624: Experimental Crystal Structure Determination

Related Article: M. Paz Claresa, Carolina Serena, Salvador Blasco, Aida Nebot, Lucas del Castillo, Conxa Soriano, Antonio Domènech, Ana Virginia Sánchez-Sánchez, Laura Soler-Calero, José Luis Mullor, Antonio García-España, Enrique García-España|2015|J.Inorg.Biochem.|143|1|doi:10.1016/j.jinorgbio.2014.11.001

CCDC 2017310: Experimental Crystal Structure Determination

Related Article: Álvaro Martínez-Camarena, Matteo Savastano, José M. Llinares, Begoña Verdejo, Antonio Bianchi, Enrique García-España, Carla Bazzicalupi|2020|Inorg.Chem.Front.|7|4239|doi:10.1039/D0QI00912A

CCDC 2192965: Experimental Crystal Structure Determination

Related Article: Valeria Dantignana, M. Carmen Pérez-Segura, Pau Besalú-Sala, Estefanía Delgado-Pinar, Álvaro Martínez-Camarena, Joan Serrano-Plana, Andrea Álvarez-Núñez, Carmen E. Castillo, Enrique García-España, Josep M. Luis, Manuel G. Basallote, Miquel Costas, Anna Company|2023|Angew.Chem.,Int.Ed.|62||doi:10.1002/anie.202211361

CCDC 1468807: Experimental Crystal Structure Determination

Related Article: Javier Pitarch-Jarque, Raquel Belda, Salvador Blasco, Pilar Navarro, Roberto Tejero, José Miguel Junquera-Hernández, Vicente Pérez-Mondéjar, Enrique García-España|2016|New J.Chem.|40|5670|doi:10.1039/C5NJ03234B

CCDC 983272: Experimental Crystal Structure Determination

Related Article: Javier Pitarch-Jarque, Raquel Belda, Francesc Lloret, Jesús Ferrando-Soria, Pilar Navarro, Alberto Lopera, Enrique García-España|2015|Dalton Trans.|44|3378|doi:10.1039/C4DT03650F

CCDC 1472832: Experimental Crystal Structure Determination

Related Article: Luis M. López-Martínez, Javier Pitarch-Jarque, Àlvar Martínez-Camarena, Enrique García-España, Roberto Tejero, Hisila Santacruz-Ortega, Rosa-Elena Navarro, Rogerio R. Sotelo-Mundo, Mario Alberto Leyva-Peralta, Antonio Doménech-Carbó, and Begoña Verdejo|2016|Inorg.Chem.|55|7564|doi:10.1021/acs.inorgchem.6b01006

CCDC 983271: Experimental Crystal Structure Determination

Related Article: Javier Pitarch-Jarque, Raquel Belda, Francesc Lloret, Jesús Ferrando-Soria, Pilar Navarro, Alberto Lopera, Enrique García-España|2015|Dalton Trans.|44|3378|doi:10.1039/C4DT03650F

CCDC 2192964: Experimental Crystal Structure Determination

Related Article: Valeria Dantignana, M. Carmen Pérez-Segura, Pau Besalú-Sala, Estefanía Delgado-Pinar, Álvaro Martínez-Camarena, Joan Serrano-Plana, Andrea Álvarez-Núñez, Carmen E. Castillo, Enrique García-España, Josep M. Luis, Manuel G. Basallote, Miquel Costas, Anna Company|2023|Angew.Chem.,Int.Ed.|62||doi:10.1002/anie.202211361

CCDC 892315: Experimental Crystal Structure Determination

Related Article: Javier Pitarch-Jarque, Raquel Belda, Salvador Blasco, Pilar Navarro, Roberto Tejero, José Miguel Junquera-Hernández, Vicente Pérez-Mondéjar, Enrique García-España|2016|New J.Chem.|40|5670|doi:10.1039/C5NJ03234B

CCDC 1431345: Experimental Crystal Structure Determination

Related Article: Alexander Ganß, Raquel Belda, Javier Pitarch, Richard Goddard, Enrique García-España, and Stefan Kubik|2015|Org.Lett.|17|5850|doi:10.1021/acs.orglett.5b03027

CCDC 983274: Experimental Crystal Structure Determination

Related Article: Javier Pitarch-Jarque, Raquel Belda, Francesc Lloret, Jesús Ferrando-Soria, Pilar Navarro, Alberto Lopera, Enrique García-España|2015|Dalton Trans.|44|3378|doi:10.1039/C4DT03650F

CCDC 1053439: Experimental Crystal Structure Determination

Related Article: Tamires S. Fernandes, Ramon S. Vilela, Ana K. Valdo, Felipe T. Martins, Enrique García-España, Mario Inclán, Joan Cano, Francesc Lloret, Miguel Julve, Humberto O. Stumpf, and Danielle Cangussu|2016|Inorg.Chem.|55|2390|doi:10.1021/acs.inorgchem.5b02786

CCDC 1994847: Experimental Crystal Structure Determination

Related Article: Javier Pitarch-Jarque, Hermas R. Jiménez, Elina Kalenius, Salvador Blasco, Alberto Lopera, M. Paz Clares, Kari Rissanen, Enrique García-España|2021|Dalton Trans.|50|9010|doi:10.1039/D1DT01302E

CCDC 1529591: Experimental Crystal Structure Determination

Related Article: Gianluca Ambrosi, M. Paz Clares, Isabel Pont, Mauro Formica, Vieri Fusi, Angela Ricci, Paola Paoli, Patrizia Rossi, Enrique García-España, Mario Inclán|2020|Dalton Trans.|49|1897|doi:10.1039/C9DT04764F

CCDC 1827337: Experimental Crystal Structure Determination

Related Article: Álvaro Martínez-Camarena, Andrea Liberato, Estefanía Delgado-Pinar, Andrés G. Algarra, Javier Pitarch-Jarque, José M. Llinares, M. Ángeles Mañez, Antonio Domenech-Carbó, Manuel G. Basallote, Enrique García-España|2018|Inorg.Chem.|57|10961|doi:10.1021/acs.inorgchem.8b01492

CCDC 1840192: Experimental Crystal Structure Determination

Related Article: Ruixi Fan, Joan Serrano-Plana, Williamson N. Oloo, Apparao Draksharapu, Estefanía Delgado-Pinar, Anna Company, Vlad Martin-Diaconescu, Margarida Borrell, Julio Lloret-Fillol, Enrique García-España, Yisong Guo, Emile L. Bominaar, Lawrence Que Junior, Miquel Costas, Eckard Münck|2018|J.Am.Chem.Soc.|140|3916|doi:10.1021/jacs.7b11400

CCDC 1036385: Experimental Crystal Structure Determination

Related Article: Joan Serrano-Plana, Williamson N. Oloo, Laura Acosta-Rueda, Katlyn K. Meier, Begoña Verdejo, Enrique García-España, Manuel G. Basallote, Eckard Münck, Lawrence Que Junior, Anna Company, and Miquel Costas|2015|J.Am.Chem.Soc.|137|15833|doi:10.1021/jacs.5b09904

CCDC 1912382: Experimental Crystal Structure Determination

Related Article: Javier Pitarch-Jarque, Kari Rissanen, Santiago García-Granda, Alberto Lopera, M. Paz Clares, Enrique García-España, Salvador Blasco|2019|New J.Chem.|43|18915|doi:10.1039/C9NJ05231C

CCDC 1953929: Experimental Crystal Structure Determination

Related Article: Alberto Lopera, Ariadna Gil-Martínez, Javier Pitarch-Jarque, Begoña Verdejo, Salvador Blasco, M. Paz Clares, Hermas R. Jiménez, Enrique García-España|2020|Dalton Trans.|49|8614|doi:10.1039/D0DT01056A

CCDC 953540: Experimental Crystal Structure Determination

Related Article: Sandra Gago, Jorge González, Salvador Blasco, A. Jorge Parola, M. T. Albelda, Enrique García-España, Fernando Pina|2014|Dalton Trans.|43|2437|doi:10.1039/C3DT52061G

CCDC 1053438: Experimental Crystal Structure Determination

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CCDC 983273: Experimental Crystal Structure Determination

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CCDC 892316: Experimental Crystal Structure Determination

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CCDC 1827336: Experimental Crystal Structure Determination

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