Synthesis and antimicrobial activities of copper(II) complexes of N(4),N(11)-dimethyl (LBZ & LCZ) and N(4)-monomethyl (LCZ1)-3,5,7,7,10,12,14,14-octamethyl-1,4,8,11-tetraazacyclotetradecane. Crystal and molecular structure of [CuLCZ1](ClO4)2

Abstract

Naturally occurring azamacrocyclic metal complexes such as haems, chlorophyll, vitamin B12, and the factor F430 carry pendent ring substituemts and axial co-ligands that act as functional components in these important biological systems. Design of related systems with structural features related to their natural counterparts is thus a multifarious challenge. With this in mind, we have recently reported on the characterization and antimicrobial activities of tetraazacyclotetradecanes and their Ni2+ complexes. Here, we present results on modified N-pendent ligands and their Cu2+ complexes: The interaction of two isomers of 3,5,7,7,10,12,14,14-octamethyl-1,4,8,11-tetraazacyclotetradecane, LB and LC (differing in the orientation of the CH3 groups on the chiral C atoms), with CH3I resulted in the substitution of the N(4) and N(11) protons by CH3, forming the dimethyl derivatives LBZ and LCZ, when reacted with CH3I in the ratio 1:2, yielded the N(4) monomethyl derivative LCZ1. On reaction with Cu(ClO4)2·6H2O, the square-planar complexes [CuL](ClO4)2 (L=LBZ, LCZ, or LCZ1).) were obtained. The complex cations [CuLBZ]+ and [CuLCZ]+ undergo axial ligand addition with the anions X=NCS−, NO2−, NO3− Cl−, Br− and I− to form six-coordinate trans-[CuL′X2] (L′=LBZ or LCZ). The compounds have been characterized on the basis of analytical, spectroscopic, conductometric and magnetochemical data. The structure of [CuLCZ1](ClO4)2 {space group Pn, No. 2, a=10.3581(12), b=8.8335(10), c=14.2584(16)Å; β=99.917(3) (2)°} has been determined by X-ray crystallography. The copper centre is coordinated to an N4 donor set of LCZ1 in a square planar geometry. The antifungal and antibacterial activities of the compounds have been studied against some phyto-pathogenic fungi and bacteria. Generally, the complexes exhibit a more pronounced antimicrobial activity than the parent ligands.