The synthesis, crystal structures and antimicrobial studies of C-methyl-substituted hexaaza macrocycle of Cu(II) having aromatic pendant arm

Abstract

Cu(II) complexes of 14-membered hexaaza macrocyclic ligand with C-methyl substituent of the type [CuL](X)2 (where L = 3,10-bisbenzyl-6,13- dimethyl-1,3,5,8,10,12-hexaazacyclotetradecane, and X = ClO4-, PF6-) were synthesized by tandem reaction. They were characterized by spectral and single-crystal X-ray diffraction techniques. The complexes show distorted octahedral geometry and the counter ions are weakly coordinated to the metal ion at the axial positions. The macrocyclic ring adopts the trans-III configuration with six- and five-membered chelate rings in chair and gauche conformation, respectively. It was observed that in the solid state the arrangement of the coordination sphere is distorted octahedral whereas, in solution, a square-planar structure is predominant. The molar conductance of the complexes indicates that the axially bonded anions are almost dissociated in acetonitrile solution. The Electron Paramagnetic Resonance (EPR) spectrum of complex 1 is axial and consistent with a dx2 - y2 ground state. The [CuL](ClO 4)2 was found to be active against the tested microorganism. © 2011 John Wiley & Sons, Ltd.