Synthesis, characterization and antifungal activity of group 12 metal complexes of 2-acetylpyridine-4N-ethylthiosemicarbazone (H4EL) and 2-acetylpyridine-N-oxide-4N-ethylthiosemicarbazone (H4ELO)

Reaction of group 12 metal halides in ethanol with the thiosemicarbazones 2-acetyrpyridine-N-4-ethylthiosemicarbazone (H4EL) and 2-acetylpyridine-N-oxide-N-4-ethylthiosemicarbazone (H4ELO) produced the compounds [M(H4EL)X-2] and [M(H4ELO)X-2] [M=Zn(II), Cd(II) or Hg(II), X=Cl, Br or I]. The ligands and complexes were characterized by elemental analysis and by IR and NMR (H-1, C-13, Cd-113, Hg-199) Spectroscopy, and the structures of H4ELO . H2O and the complexes [Cd(H4EL)I-2]. 2DMSO, [Hg(H4EL)Br-2]-DMSO, [Zn(H4ELO)Cl-2] and [Zn(H4ELO)Br-2] were determined by X-ray diffraction. The metal centers in the complexes have coordination number five, H4EL and H4ELO behaving as neutral NNS- and ONS-tridentate ligands, respectively. The coordination polyhedra are close to tetragonal pyramids, the degree of distortion towards trigonal bipyramids was estimated by tau calculation. Against the pathogenic fungi Aspergillus niger and Paecilomyces variotii, the mercury complexes of H4ELO had activities that at some doses exceeded that of nystatin. (C) 1999 Elsevier Science Ltd. All rights reserved.