Magnetic properties and antibacterial activity of tetranuclear copper complexes bridged by oxo group

Abstract

A series of three tetranuclear Cu(II) complexes of general formula [Cu 4OCl6L4], where L is a Lewis Base ligand has been characterized through magnetic measurements and determination of antimicrobial activities. This study include the following species [Cu 4OCl6)Cl(PhIm)3](HPhIm)·H2O (1) where PhIm= 4-phenylimidazole, [(Cu4OCl6)(PyNO) 4]·1/5(H2O) (2) where PyNO= Pyridine-N-oxide and [(Cu4OCl6) (MeIm)4]·3(CH3OH) (3) where MeIm = 2-methylimidazole. The polynuclear cluster in the complexes contains a central oxygen atom tetrahedral coordinated to four copper(II) ions, each of which coordinates a monodentate L ligand. Each pair of copper atoms is bridged by on a chlorine ion, resulting a trigonal bipiramidal environment. The variable temperature magnetic susceptibilities of these complexes were investigated in the temperature range 5-300K. Satisfactory fits to the observed susceptibility data were obtained only for the complexes (1) and (3), by assuming Isotropic magnetic exchange interactions and using the appropriate spin Hamiltonian and susceptibility equation giving the coupling constants J 1= 0.148cm-1, J2= -1.707 cm-1 for (1) and J1= 0.522 cm-1, J2= -5.32 cm -1 for (3). The antimicrobial activities of these complexes have been screened in vitro against Gram positive and negative bacteria. © 2006 Sociedad Chilena de Química.