Search

Abstract: A binuclear acylhydrazine bridged Cu(II) complex, [Cu2(L)(NO3)3(H2O)] (1), and an anti-orthogonal binuclear oxovanadium(V) complex, [V2O4(L)2] (2), have been synthesized and characterized spectroscopically and crystallographically. The ligand HL has two potentially bridging functional groups (μ-O, μ-N–N) and consequently can exist in the following coordination conformers: (a) metal centers bridged by μ-O, (b) metal centers bridged by μ-N–N. A rare acylhydrazine bridged (a) type configuration exists in the dinuclear Cu(II) complex 1. The bridging ligand mediates a strong antiferromagnetic coupling (J =−99cm−1). The exchange pathway parameters have also been evaluated from density functional theoretical calculations to corroborate the bridging signatures with experimental findings (J =−93.96cm−1). Molecule 2 has a centrosymmetric structure with each vanadium center having a distorted octahedral geometry. It shows a one step irreversible reduction at +0.43V. The bond angles, bond lengths and torsion angles in 2 are correlated with DFT. [Copyright &y& Elsevier]

The exchange coupled site behaves as a good structural and functional model for type 3 active site in copper oxidases and is both efficient and selective catalyst for oxidation of diphenols. [Display omitted] A new copper(II) complex, [Cu 2 (L1)(µ-Cl) 2 ] 2 (C1), of the binucleating 2,6-bis((2-(4′-imidazolyl)ethyl)aminomethylidene)-4-methylphenol (HL1) with N 4 O binding sites, has been synthesized to investigate as potential structural and functional model for catecholase activity of the dicopper(II) site. It has been characterized by spectroscopic techniques and X-ray crystallography. The complex C1 exists as chlorido bridged dimer of binuclear copper(II) units, each possessing one end-off compartmental ligand (L1) with endogenous µ-phenoxido and exogenous µ-chlorido groups leading to intermetallic distance Cu1···Cu2 of 3.129 Å and Cu1-O1(phenoxo)-Cu2 angle of 107.67(10)o. Each copper(II) center has distorted octahedral geometry with bridging by chlorides in the tetranuclear dimer. The crystal system is monoclinc with space group P 2 1 / c. Magnetic measurements reveal that C1 is strongly antiferromagnetically coupled with J = − 115.663 ± 0.82547 cm−1. The catecholase activity of the complex has been evaluated by oxidation of 3,5-di(tert -butyl)catechol and 4-methyl catechol to the corresponding quinones under aerobic conditions. A kinetic treatment on the basis of the Michaelis-Menten model has been applied for the kinetic study. The complex is found to be selective for the substrates with higher V max = 8.2726x10−8 M s−1 and K m = 0.0107 M for 3,5-DTBC at 30 °C as compared to V max = 5.0371x10−8 M s−1 and K m = 0.027 M for 4-methyl catechol at 50 °C while it is found to be practically inactive for dopamine, 2,3-dihydroxy naphthalene and pyrocatechol oxidation. [ABSTRACT FROM AUTHOR]

Abstract: The search for efficient artificial nucleases is a consequence of the huge efforts towards DNA sequencing by genome projects around the world. In the present study, we describe the activity of the Cu(II)–BMXD complex (BMXD=3,6,9,17,20,23-hexaazatricyclo[23.3.1.111,15]triaconta-1(29),11(30),12,14,25,27-hexaene) as a DNA cleavage agent. The rate constant for the DNA backbone cleavage reaction at room temperature (25°C) and pH 7.0 was estimated to be 1.1×10−6 s−1, which corresponds, approximately, to a half-life (t 1/2) of one week. We demonstrated that the DNA cleavage reaction promoted by the Cu2BMXD complex may occur via an oxidative pathway through performing reactions in the presence of free-radical acceptors and comparing the activity under aerobic and anaerobic conditions. The Cu2BMXD complex reported here is established as a novel artificial nuclease. [Copyright &y& Elsevier]

A dicopper complex of a Schiff's base, 2-[(4-methyl-pyridin-2-ylimino)-methyl]-phenol, with a bridging acetato ligand has been synthesized and characterized by single crystal XRD, EPR, magnetic susceptibility, IR, UV–Vis, CV and elemental analysis. The X-ray analysis indicates that the system belongs to the triclinic space group P1¯. One of the copper atoms in the binuclear complex adopts a square-pyramidal geometry consisting of the tridentate N-salicylidimine dianions, the neutral monodentate pyridine ligand in the basal plane and the solvent molecule in the apical position, while the other copper assumes a square-planar geometry. A seven line pattern observed at half-field in the frozen solution EPR spectrum confirms the interaction between the two copper ions. The cyclic voltametric studies point to a two-step electron transfer indicating the reduction of the two copper ions to copper(I), i.e., Cu(II)Cu(II) ↔ Cu(II)Cu(I) ↔ Cu(I)Cu(I). The molar conductance for the complex measured in methanol solvent indicates that the complex is a 1:1 electrolyte. [Copyright &y& Elsevier]