Synthesis, spectral properties, crystal structures and biological activity of copper(II) pyridinecarboxylates with N -heterocyclic ligands

Abstract

Synthesis and characterization of four new 2,6-dimethoxynicotinate (2,6-(MeO)2nic) copper(II) monomeric complexes [Cu(2,6-(MeO)2nic)2(py)2] (py is pyridine), [Cu{2,6-(MeO)2nic}2(Etnic)2(H2O)] (Etnic is ethylnicotinate), [Cu{2,6-(MeO)2nic}2(Et2nia)2(H2O)2] (Et2nia is N,N-diethylnicotinamide) as well as of the polymeric complex [Cu{2,6-(MeO)2nic}2(ron)2] n (ron is ronicol) are reported. The characterizations were based on elemental analysis, infrared, electronic and EPR spectra. Crystal structures of two of the complexes have been determined. The copper(II) of [Cu{2,6-(MeO)2nic}2(py)2] has a distorted tetragonal-bipyramidal (4 + 2) coordination environment. Both 2,6-(MeO)2nic anions are asymmetrically chelating. The Cu(II) of [Cu{2,6-(MeO)2nic}2(Etnic)2(H2O)] is pentacoordinate in a slightly distorted tetragonal-pyramidal arrangement by two trans nitrogens, each of one Etnic, by two oxygens, each of the carboxyl group of one unidentate 2,6-(MeO)2nic and the axial position occupied by water at a longer distance. Antimicrobial effects of the complexes have been tested on various strains of bacteria, yeasts and filamentous fungi. While the 2,6-(MeO)2nicH alone did not influence the model bacteria growth, dimeric [Cu{2,6-(MeO)2nic}2(H2O)]2 and polymeric [Cu{2,6-(MeO)2nic}2(ron)2] n have pronounced influence on the growth of Staphylococcus aureus, Escherichia coli and Candida parapsilosis.