Synthesis, characterization, antifungal properties and X-ray crystal structures of five- and six-coordinate copper(II) complexes of the 6-methyl-2-formylpyridine4N-dimethylthiosemicarbazone

Copper(II) complexes of formulas, [Cu(NNS)(NO3)(H2O)].H2O and [Cu(NNS)(2)] (NNS = anionic form of the 6-methyl-2formylpyridine(4)N-dimethylthiosemicarbazone) have been synthesized and characterized by a variety of physico-chemical techniques. Magnetic and spectroscopic data support a five-coordinate structure for the [Cu(NNS)(NO3)(H2O)].H2O complex and a distorted octahedral structure for the [Cu(NNS)(2)] complex. The crystal structures of both complexes have also been determined by X-ray diffraction. The mono-ligated nitrate-complex has a five-coordinate geometry, with the thiosemicarbazone ligand coordinated to the copper(II) ion as a uninegatively charged NNS tridentate chelating agent via the pyridine nitrogen atom, the azomethine nitrogen atom and the thiolate sulfur atom. The fourth and fifth coordination positions around the copper(II) ion are occupied by the nitrate and aqua ligands, respectively. The bis-ligand copper(II) complex, [Cu(NNS)(2)] has a distorted octahedral structure with two uninegatively charged tridentate NNS thiosemicarbazone ligands coordinated to the copper(II) ion via the pyridine nitrogen atoms, the azomethine nitrogen atoms and the mercaptide sulfur atoms in a meridional arrangement. The ligand is fungitoxic against the phytopathogenic fungi, A. alternata, F.equiseti and M. phaseolina but the complexes are less active than the free ligand. (C) 2001 Published by Elsevier Science Ltd.