Synthesis, electrochemical, magnetic, catalytic and antimicrobial studies of N-functionalized cyclam based trinuclear copper(II) and nickel(II) complexes

Abstract

Trinuclear copper(II) and nickel(II) complexes have been prepared by using Schiff base ligands derived from 1,8-[bis(3-formyl-2-hydroxy-5-methyl) benzyl]-4,11-dimethyl-l,4,8,11-tetraazacyclotetradecane, and 1,8-[bis(3-formyl-2-hydroxy-5-bromo)benzyl]-4,11-dimethyl-l,4,8,11-tetraazacyclotetradecane with aliphatic and aromatic diamines. All the complexes were characterized by elemental and spectroscopic analysis. Electrochemical studies of the copper(II) complexes in DMF solution show three irreversible one electron reduction process around E pc 1 = −0.59 to −0.80 V, E pc 2 = −0.89 to −1.14 V and E pc 3 = −1.17 to −1.29 V, and for nickel(II) complexes it is around E pc 1 = −0.63 to −0.77 V, E pc 2 = −1.20 to −1.35 V and E pc 3 = −1.60 to −1.74 V. ESR spectra and magnetic moments of the trinuclear Cu(II) complexes show the presence of antiferromagnetic coupling. Cryomagnetic investigation of the trinuclear copper(II) complexes show that the observed −2J values are in the range of 116–178 cm−1. The rate constants for hydrolysis of 4-nitrophenylphosphate by the complexes are in the range of 2.68 × 10−2 to 9.81 × 10−2 min−1. The rate constants values for the catecholase activity of the copper(II) complexes fall in the range of 3.03 × 10−2 to 9.32 × 10−2 min−1. All the complexes.