Synthesis, spectroscopic properties, crystal structure and biological activities of copper(II) 2-methylthionicotinate complexes with furopyridines

Abstract

The synthesis and characterization of six new 2-methylthionicotinate (2-MeSnic) copper(II) monomeric complexes [Cu(2-MeSnic)2L2] (L is furo[3,2-c]pyridine—fpy, 2-methylfuro[3,2-c]pyridine—Mefpy, 2,3-dimethylfuro[3,2-c]pyridine—Me2fpy or benzo[4,5]furo[3,2-c]pyridine—Bfp), [Cu(2-MeSnic)2(fpy)2(H2O)], as well as [Cu(2-MeSnic)2(CF3Phfpy)2(H2O)2] (CF3Phfpy is 2-(3-trifluoromethylphenyl)furo[3,2-c]pyridine) are reported. The characterizations were based on elemental analysis, infrared, electronic and EPR spectra. The crystal structure of one of the complexes has been determined. The CuII atoms of [Cu(2-MeSnic)2(fpy)2(H2O)] are six-coordinated in a highly distorted tetragonal–bipyramidal arrangement by two nitrogen atoms, one from each fpy, in trans-positions, by three oxygen atoms of the carboxyl groups of 2-MeSnic ligands (one monodentate, one asymmetrically bidentate), one axial position being occupied by the oxygen of a water molecule. The antimicrobial effects have been tested on various strains of bacteria, yeasts and filamentous fungi. A comparison of the IC50 and MIC values has shown a decrease of inhibition activities of tested compounds in the order: [Cu(2-MeSnic)2(Bfp)2] > Bfp > [Cu(2-MeSnic)2(CF3Phfpy)2(H2O)2] > [Cu(2-MeSnic)2(Me2fpy)2] > CF3Phfpy > [Cu(2-MeSnic)2(Mefpy)2] > Me2fpy > [Cu(2-MeSnic)2(fpy)2(H2O)] > [Cu(2-MeSnic)2(H2O)]2 > Mefpy > fpy = 2-MeSnicH = CuSO4.