Novel unsymmetrical macrocyclic dicompartmental binuclear copper(II) complexes bearing 4- and 6-coordination sites: Electrochemical, magnetic, catalytic and antimicrobial studies

Abstract

A series of novel unsymmetrical dicompartmental binuclear copper(II) complexes have been prepared by the simple Schiff-base condensation of the compound 1,8-[bis(3-formyl-2-hydroxy-5-methyl)benzyl]-l,4,8,11-tetraazacyclotetradecane (L) with the appropriate aliphatic or aromatic diamines, copper(II) perchlorate and triethylamine. All the complexes were characterized by elemental and spectral analysis. The electronic spectra of the complexes show the d–d transition in the range 555–672 nm. Electrochemical studies of the complexes show two irreversible one electron reduction processes around E pc 1 = - 0.60 to - 0.91 V and E pc 1 = - 0.94 to - 1.26 V . The reduction potential of the binuclear copper(II) complexes shift anodically upon increasing chain length of the macrocyclic ring. ESR spectra of the binuclear copper(II) complexes show a broad signal at g = 2.10 and μ eff values in the range 1.31–1.55 BM, which convey the presence of antiferromagnetic coupling. Cryomagnetic investigation of the binuclear complexes shows that the observed −2 J values are in the range 154–236 cm −1. The observed rate constant values for hydrolysis of 4-nitrophenylphosphate are in the range 2.18 × 10 −2–10.09 × 10 −2 min −1 and for catecholase activity they are in the range 2.09 × 10 −2–7.19 × 10 −2 min −1. All the complexes were screened for antifungal and antibacterial activity.