Structure, magnetic properties and catecholase activity study of oxo-bridged dinuclear copper(II) complexes

Six alkoxy-bridged dinuclear copper(II) complexes with catecholase-like sites, [Cu(L1)(NCS)]2 (1), [Cu(L2)(CH3CO2)]2·2H2O (2), [Cu(L3)(NCO)]2 (3), [Cu(L4)(NCS)]2 (4), [Cu(L5)(NCS)]2 (5), and [Cu(L4)(Cl)]2 (6), where HL1=2-(hydroxymethyl)-pyridine, HL2=6-methyl-2-pyridine-methanol, HL3=2-(2-hydroxyethyl)-pyridine, HL4=1-dimethylamino-2-methyl-1-propanol, and HL5=1-dimethylamino-2-propanol, respectively), have been prepared and characterized. The single crystal X-ray analysis show that the structures of complexes 1–6 are dimeric with two adjacent copper(II) atoms bridged by pairs of μ-oxy atoms from the alkoxyl group of the ligands. Magnetic susceptibility measurements in the temperature range 2–300 K for complexes 1–6 indicate significant antiferromagnetic coupling between the copper(II) atoms. The kinetic studies on catecholase activity of complexes for the oxidation of 3,5-di-tert-butylcatechol by O2 was studied and it found that the complexes with the bond distance of Cu(II)⋯Cu(II) located near 2.98 to ∼2.99 Å show high catecholase activity. The reaction rate constant for the catecholase activity was obtained by Michaelis–Menten model.