New copper(II) μ-alkoxo-μ-carboxylato double-bridged complexes as models for the active site of catechol oxidase: synthesis, spectral characterization and DFT calculations()

A series of four copper(II) μ-Alkoxo-μ-carboxylato double bridged complexes, [{Cu(2)(L)}(2)][(μ–O(2)C–CO(2)] 1, [{Cu(2)(L)}(2)(μ–O(2)C–(CH(2))CO(2)] 2, [{Cu(2)(L)}(2)(μ–O(2)C–CH(2)–CO(2)] 3 and [{Cu(2)(L)}(2)(μ–O(2)C–C(6)H(4)–CO(2)] 4 (H(3)L = 4-bromo-2-((E)-((3-(((E)-5-chloro-2-hydroxybenzylidene) amino)-2-hydroxypropyl) imino) methyl)-6-methoxyphenol and μ-dicarboxylate ions = oxalate, malonate, succinate and terephthalate) have been synthesized and characterized using several physicochemical techniques. The tridentate nature of H(3)L is interpreted from IR spectra. The Epr spectra of these complexes are characteristic of the quintet state (S = 2) in central features and the triplet state (S = 1) of these tetranuclear complexes. The electrochemical potential of these complexes was investigated using CV (cyclic voltammetry) and DPV (differential pulse voltammetry). All complexes showed quasi reversible reduction peaks in the cathodic region. To explore the stability of these complexes, quantum chemical parameters like electronegativity, ionization potential, electron affinity, global hardness and softness, and electrophilicity were estimated and discussed. The synthesized complexes have been designed as structural and functional models of the catechol oxidase enzymes to investigate the catecholase activity. Additionally, superoxide dismutase activity data of all complexes have also been evaluated and compared with known SOD mimics.