Copper(II) pyridinecarboxylate adducts with chelating ligands as potential antimicrobial agents

Abstract

The synthesis and characterization of seven new solid complexes, [Cu(2-MeSnic) 2 (phen)] (2-MeSnic = 2-methylthionicotinate, phen = 1,10-phenanthroline), [CuX 2(bipy)(H 2O)] (X = 2-MeSnic or nic (nicotinate), bipy = 2,2′-bipyridine), [Cu(isonic) 2(bipy)(H 2O)] · H 2O (isonic = isonicotinate), [Cu(bipy) 2(H 2O)](2-MeSnic) 2 · 3H 2O, [Cu(phen) 2(H 2O)](isonic) 2 · 2H 2O and [Cu(phen) 2(H 2O)](nic) 2 · 3H 2O, are reported. The composition and stereochemistry as well as the mode of ligand coordination have been determined by elemental analysis, IR, electronic and EPR spectra. The carboxyl group of the pyridinecarboxylate anions coordinates to the Cu(II) atom as an unidentate or as a chelating ligand. The EPR spectra of studied complexes are monomeric except for the spectrum of [Cu(2-MeSnic) 2(bipy)(H 2O)], which shows triplet state feature. Half-field transition, observed for [Cu(2-MeSnic) 2(bipy)(H 2O)], [Cu(bipy) 2(H 2O)](2-MeSnic) 2 · 3H 2O and [Cu(phen) 2(H 2O)](nic) 2 · 3H 2O, was used to estimate the interspin copper–copper distances. In all cases, the available evidence supports square-pyramidal environment about the copper(II) atom, which is confirmed by crystal and molecular structure of one of the products, namely [Cu(2-MeSnic) 2(bipy)(H 2O)]. The antimicrobial effects have been tested on various strains of bacteria, yeasts and filamentous fungi.