0000000000033464
AUTHOR
Juan F. Miravet
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, …
Synthesis, spectroscopic studies and biological evaluation of acridine derivatives: The role of aggregation on the photodynamic efficiency.
Two new photoactive compounds (1 and 2) derived from the 9-amidoacridine chromophore have been synthesized and fully characterized. Their abilities to produce singlet oxygen upon irradiation have been compared. The synthesized compounds show very different self-aggregating properties since only 1 present a strong tendency to aggregate in water. Biological assays were conducted with two cell types: hepatoma cells (Hep3B) and human umbilical vein endothelial cells (HUVEC). Photodynamic therapy (PDT) studies carried out with Hep3B cells showed that non-aggregating compound 2 showed photoxicity, ascribed to the production of singlet oxygen, being aggregating compound 1 photochemically inactive.…
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.
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.
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.
High Optical Performance of Cyan‐Emissive CsPbBr3 Perovskite Quantum Dots Embedded in Molecular Organogels
This is the pre-peer reviewed version of the following article: High Optical Performance of Cyan‐Emissive CsPbBr3 Perovskite Quantum Dots Embedded in Molecular Organogels, which has been published in final form at https://doi.org/10.1002/adom.202001786. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions." Perovskite quantum dots (PQDs) have fascinating optoelectronic properties, such as high photoluminescence quantum yield (PLQY) for a broad range of materials, and the possibility to obtain different bandgaps with the same material or halide combinations. Nevertheless, blue‐emissive materials generally present…
Structural Studies on Polyaza[n]paracyclophanes. A Molecular Mechanics and Crystallographic Study
Abstract Structural analysis of polyaza[n]paracyclophanes 1-5 has been carried out by the use of molecular mechanics and other techniques. NMR data and molecular mechanics calculations show that conformations in which the polyamine chain is arching above the aromatic ring are prevalent in solution. The crystal structure of triprotonated durene derivative 2b agrees with those studies. Crystals of 3H+.2b are triclinic, space group P1, with a = 11.758(4) A, b = 13.870(5) A, c = 17.181(3) A, α = 96.66(2)°, β = 106.02(2)°, γ = 104.87(3)°, Z = 4, R1 = 0.072, wR2 = 0.18. Three different conformations are present in the crystal. Good agreement between the crystal structures and calculated conformat…
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.
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.
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…
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.
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.
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…
Self-assembled multivalent (SAMul) ligand systems with enhanced stability in the presence of human serum
Self-assembled cationic micelles are an attractive platform for binding biologically-relevant polyanions such as heparin. This has potential applications in coagulation control, where a synthetic heparin rescue agent could be a useful replacement for protamine, which is in current clinical use. However, micelles can have low stability in human serum and unacceptable toxicity profiles. This paper reports the optimi- sation of self-assembled multivalent (SAMul) arrays of amphiphilic ligands to bind heparin in competitive conditions. Specifically, modification of the hydrophobic unit kinetically stabilises the self-assembled nanostructures, preventing loss of binding ability in the presence of…
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…
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.