Syntheses electronic structures and EPR/UV–vis–NIR spectroelectrochemistry of nickel(II) copper(II) and zinc(II) complexes with a tetradentate ligand based on S-methylisothiosemicarbazide

摘要

Template condensation of 3,5-di-tert-butyl-2-hydroxybenzaldehyde S-methylisothiosemicarbazone with pentane-2,4-dione and triethyl orthoformate at elevated temperature resulted in metal complexes of the type M^IIL, where M = Ni, Cu and H2L = novel tetradentate organic ligand. These complexes are relevant to the active site of the copper enzymes galactose oxidase and glyoxal oxidase. Demetallation of Ni^IIL with gaseous hydrogen chloride in chloroform afforded the metal-free ligand H2L. Then by the reaction of H2L with Zn(CH3COO)2·2H2O in 1:1 molar ratio in chloroform/methanol 1:2 the complex Zn^IIL(CH3OH) was prepared. The three metal complexes and the prepared ligand were characterized by spectroscopic methods (IR, UV–vis and NMR spectroscopy), X-ray crystallography and DFT calculations. Electrochemically generated one-electron oxidized metal complexes [NiL]⁺, [CuL]⁺ and [ZnL(CH3OH)]⁺ and the metal-free ligand cation radical [H2L]^+• were studied by EPR/UV–vis–NIR and DFT calculations. These studies demonstrated the interaction between the metal ion and the phenoxyl radical.