Complexes of Group 12 Metals with 2-Acetylpyridine 4N-Dimethylthiosemicarbazone and with 2-Acetylpyridine-N-oxide 4N-Dimethylthiosemicarbazone: Synthesis, Structure and Antifungal Activity

Abstract

Reaction in ethanol of group 12 metal halides with 2-acetylpyridine 4N-dimethylthiosemicarbazone (H4DML) and with 2-acetylpyridine-N-oxide 4N-dimethylthiosemicarbazone (H4DMLO) afforded complexes of the forms [M(H4DML)X2] (1 - 9) and [M(H4DMLO)X2] (10 - 18) (M = ZnII, CdII or HgII; X = Cl, Br or I). H4DMLO and the complexes of both thiosemicarbazones have been characterized by elemental analysis and by IR and 1H, 13C and 113Cd NMR spectroscopy, and the crystal structures of [Cd(H4 DML)Cl2 ] (4), [Cd(H4 DML)l2 ] (6), H4DMLO, [Hg(H4DMLO)Cl2] (16) and [Hg(H4 DMLO)Br2] (17) have been determined by X-ray diffractometry. In all the H4DML complexes, the thiosemicarbazone acts as an N,N,Stridentate ligand, and the coordination polyhedra of the pentacoordinate metals are more or less distorted tetragonal pyramids. H4DMLO is an 0,N,S-tridentate ligand for zinc and cadmium halides and an N,S-bidentate ligand for mercury halides, in which the mercury atom has coordination number four and a distorted trigonal pyramidal environment. In assays of antifungal activity against Aspergillus niger and Paecilomyces variotii, H4DML was more active than nystatin, and its complex with ZnCl2 also showed good activity against A. niger; neither H4DMLO nor any of its complexes inhibited the growth of either pathogen