Trinuclear CuII complex containing a new pentadentate ligand: Structure, magnetism, physicochemical properties and catecholase activity

Abstract

A new pentadentate ligand, 2-N-((bis(pyridin-2-ylmethyl)amino)methyl)-6-(methoxymethyl)-4-methylphenol (BPM3F), was synthesized and used to obtain a trinuclear copper(II) complex, [Cu3(BPM3F)2(µ-OAc)2](ClO4)2·2H2O (1). The crystal structure, magnetic, redox and spectroscopic properties of the complex were determined. In the molecular structure of the new trinuclear complex, each of the two terminal Cu(II) atoms (Cu1, Cu3) is coordinated by three nitrogen atoms of the tridentate pendant arm and the µ-phenolate oxygen atom of the pentadentate ligand BPM3F together with an oxygen atom of the µ-acetate bridge. The N,O donor ligands around the Cu1 and Cu3 centers and the intramolecular distances Cu1⋯Cu2 and Cu2⋯Cu3 are similar, resulting in a highly distorted square pyramidal geometry. The variable-temperature magnetic data in the temperature range of 2–300 K indicate weak antiferromagnetic coupling (J12 = J23 = J = −12.9 cm−1) for 1 involving the phenolate bridge between Cu1⋯Cu2 and Cu2⋯Cu3 structural units. In addition, kinetic studies on the oxidation of 3,5-di-tert-butylcatechol to 3,5-di-tert-butyl-o-benzoquinone by dioxygen reveal that complex 1 has significant catechol oxidase activity (kcat = 0.149 ± 0.009 s−1, KM = 12.99 ± 1.35 × 10−3molL−1 and kcat/KM = 11.47 ± 1.28 Lmol−1 s−1).