Search results for "Macrocyclic ligand"
showing 10 items of 21 documents
Ligand Noninnocence in Cobalt Dipyrrin–Bisphenols: Spectroscopic, Electrochemical, and Theoretical Insights Indicating an Emerging Analogy with Corro…
2019
Three cobalt dipyrrin-bisphenol (DPPCo) complexes with different meso-aryl groups (pentafluorophenyl, phenyl, and mesityl) were synthesized and characterized based on their electrochemistry and spectroscopic properties in nonaqueous media. Each DPPCo undergoes multiple oxidations and reductions with the potentials, reversibility, and number of processes depending on the specific solution conditions, the specific macrocyclic substituents, and the type and number of axially coordinated ligands on the central cobalt ion. Theoretical calculations of the compounds with different coordination numbers are given in the current study in order to elucidate the cobalt-ion oxidation state and the innoc…
Aza-macrocyclic triphenylamine ligands for G-quadruplex recognition
2018
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…
Cyclam-functionalized silica-modified electrodes for selective determination of Cu(II)
2009
Cyclam derivatives have been grafted via 1, 2 or 4 silylated arms to the surface of mesoporous silica and the resulting materials have been incorporated into carbon paste electrodes and applied to the preconcentration electroanalysis of Cu(II). Sensitive and selective detection of the target analyte was achieved owing to the attractive binding properties of this macrocyclic ligand towards Cu(II) species. Various parameters likely to affect the preconcentration and detection steps have been studied, including pH of the accumulation medium, composition of the detection solution, structure and composition of the adsorbent, accumulation time, or presence of potentially interfering species. In p…
Syntheses, Structures, Magnetic Properties, and Density Functional Theory Magneto-Structural Correlations of Bis(μ-phenoxo) and Bis(μ-phenoxo)-μ-acet…
2013
The bis(mu-phenoxo) (FeNiIII)-Ni-II compound [Fe-III(N-3)(2)LNiII(H2O)(CH3CN)](ClO4) (1) and the bis(mu-phenoxo)-mu-acetate/bis(mu-phenoxo)-bis(mu-acetate) (FeNiII)-Ni-III compound {[Fe-III(OAc)LNiII(H2O)(mu-OAc)](0.6)center dot[(FeLNiII)-L-III(mu-OAc)(2)](0.4)}(ClO4)center dot 1.1H(2)O (2) have been synthesized from the Robson type tetraiminodiphenol macrocyclic ligand H2L, which is the [2 + 2] condensation product of 4-methyl-2,6-diformylphenol and 2,2'-dimethy1-1,3-diaminopropane. Single-crystal X-ray structures of both compounds have been determined. The cationic part of the dinuclear compound 2 is a cocrystal of the two species [Fe-III(OAc)LNiII(H2O)(mu-OAc)](+) (2A) and [(FeLNiII)-L-I…
Inverted molecular cups: 1-D and 2-D Ag(I) coordination polymers from resorcinarene bis-thiacrowns
2016
Resorcinarene bis-thiacrown hosts 1–3 were prepared and crystallized with silver trifluoroacetate yielding one and two dimensional Ag coordination polymers. The complexation of silver in exo-cavity fashion folds the thiacrown bridges inwards transforming the resorcinarene hosts into inverted molecular cups. The silver cations were coordinated to the resorcinarene ligands and trifluoroacetate anions, which act as monodentate or bidendate bridging ligands between the metal ions. Argentophilic Ag⋯Ag (2.93–3.38 A) interactions supported by two bridging carboxylate anions were found in two of the structures, whereas longer Ag⋯Ag distances were observed if only one anion connected the silver cati…
Cyano-bridged structures based on [MnIIN3O2-macrocycle)]2+: a synthetic, structural, and magnetic study.
2005
Reactions between the complex [MnII(L)]2+, where L is a N3O2 macrocyclic ligand, and different cyanometalate precursors such as [M(CN)n]m- (M(III) = Cr, Fe; M(II) = Fe, Ni, Pd, Pt) lead to cyano-bridged molecular assemblies exhibiting a variety of structural topologies. The reaction between [MnII(L)]2+ and [FeII(CN)6]4- forms a trinuclear complex with formula [(MnII(L)(H2O))2(FeII(micro-CN)2(CN)4)] x 2MeOH x 10H2O (1) which crystallizes in the triclinic space group P1. The reaction between [MnII(L)]2+ and [M(II)(CN)4]2-, where M(II) = Ni (2), Pd (3), Pt (4), gives rise to three isostructural linear chain compounds with stoichiometry [(MnII(L))(M(II)(micro-CN)2(CN)2)]n and which crystallize …
Macrocyclic Pyclen-Based Gd3+ Complex with High Relaxivity and pH Response
2020
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+ …
Guidelines to design new spin crossover materials
2010
International audience; This review focuses on new families of spin crossover (SCO) complexes based on polynitrile anions as new anionic ligands or on polyazamacrocycles as neutral macrocyclic ligands. We have shown that the structural and electronic characteristics (original coordination modes and high electronic delocalization) of the polynitrile anions can be tuned by slight chemical modifications such as substitution of functional groups or variation of the negative charge to design new discrete or polymeric SCO systems.In our ongoing work on the design of new molecular systems based on new ligands that can be fine-tuned via chemical modifications, another promising way which has been r…
A novel 2,6-bis(benzoxazolyl)phenol macrocyclic chemosensor with enhanced fluorophore properties by photoinduced intramolecular proton transfer
2023
Macrocyclic ligand L, in which a 2,6-bis(2-benzoxazolyl)phenol (bis-HBO) group is incorporated in triethylenetetramine, was designed and synthesized with the aim of creating a chemosensor with high selectivity and specificity for metal cations in an aqueous environment. The availability of several proton acceptors and donors, and amine and phenol hydroxy groups, respectively, affects the keto-enol equilibrium in both the ground and excited states, and the ligand properties show dependence on the pH of the solution. L is fluorescent in the visible range, through an excited-state intramolecular proton transfer (ESIPT) mechanism. The results of an exhaustive characterization of L by spectrosco…
One-dimensional metal-organic framework with unprecedented heptanuclear copper units.
2007
The reaction of copper(II) sulfate, copper(II) chloride, 3,5-diacetylamino-1,2,4-triazole, and 3-acetylamino-5-amino-1,2,4-triazole in water yields green, plate-shaped crystals of [[{Cu3(mu3-OH(1/2))L(H2O)2Cl}2{mu-Cu(H2O)2Cl2}].12H2O]n (1), where L is a new triazole-derived macrocyclic ligand. The structure of 1 consists of heptanuclear (H)OCuII(3)-CuII-CuII(3)O(H) entities linked in pairs through symmetric mu3-O...H...O-mu3 hydrogen bonds to form a double-stranded one-dimensional network. A significant overall antiferromagnetic behavior has been observed for 1.