Reaction of 2‐acetylpyridine 4‐methylthiosemicarbazone (H4ML) with halides of zinc(II), cadmium(II), and mercury(II) afforded complexes of the form [M(H4ML)X2] [M = ZnII (1–3), CdII (4–6) or HgII (7–9); × = Cl, Br, or I]. Reaction of H4ML with K2PdCl4 and K2PtCl4 gave compounds of the form [M(4ML)Cl] [M = PdII (10) or PtII (11)]. In all the new compounds, which were characterized by elemental analyses, conductance measurements, and electronic, IR and 1H‐ and 13C‐NMR spectroscopy, and by 113Cd‐, 195Pt‐, or 199Hg‐NMR spectroscopy when relevant, the ligand is N,N,S‐tridentate, coordinating to the metal centre through its pyridine and azomethine nitrogen atoms and its thiocarbonyl sulfur atom, as was confirmed by X‐ray diffraction studies in the cases of 4· 2 DMSO, 5· 2 DMSO, 6· 2 DMSO, 7· 2 DMSO, 10, and 11. In in‐vitro assays, only [Zn(H4ML)Cl2] and [Zn(H4ML)Br2] showed some sign of antifungal activity against Aspergillus niger or Paecilomyces variotii.
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
The reaction between lead(II) acetate and 2-acetylpyridine 4N-methylthiosemicarbazone (H4ML) produced a complex of the formula [Pb(4ML)(OOCMe)] with an unusual polymeric structure in which the lead atom is hepta-coordinate, the deprotonated thiosemicarbazone is a tetradentate bridge, and the acetate group both chelates and bridges. The complex crystallizes in the triclinic space group P1̄ with a = 8.860(2), b = 9.394(2), c = 9.783(3) A, α = 108.93(4), β = 98.67(3), γ = 107.87(5)°, V = 704.1(3) Å3 , Z = 2.
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