Ricardo Domínguez

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

Abstract Reaction of group 12 metal halides in ethanol with the thiosemicarbazones 2-acetylpyridine-4N-ethylthiosemicarbazone (H4EL) and 2-acetylpyridine-N-oxide-4N-ethylthiosemicarbazone (H4ELO) produced the compounds [M(H4EL)X2] and [M(H4ELO)X2] [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 (1H, 13C, 113Cd, 199Hg) spectroscopy, and the structures of H4ELO·H2O and the complexes [Cd(H4EL)I2]·2DMSO, [Hg(H4EL)Br2]–DMSO, [Zn(H4ELO)Cl2] and [Zn(H4ELO)Br2] 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 τ 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.

Synthesis, Structural Characteristics and Biological Activities of Complexes of ZnII, CdII, HgII, PdII, and PtII with 2-Acetylpyridine 4-Methylthiosemicarbazone

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.

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

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

Aqua(IODO)(pyridine-1-oxide-2-carboxylate)cadmium(II), [Cd(C6H4NO3)I(H2O)], A compound with bidimensional supramolecular self-organization

Abstract The compound aqua(iodo)(pyridine-1-oxide-2-carboxylate)cadmium(II), [Cd(C 6 H 4 NO 3 )I(H 2 O)], which crystallizes in the monoclinic system, was prepared by reaction of cadmium(II) iodide with picolinic acid N -oxide. This compound exists as a polymeric structure in layers along the bc plane forming a supramolecular association derived from the existence of Cd—O dative bonds [2.629(7) A], and in which each cadmium atom is coordinated to the iodide ligand (Cd—I, 2.814 A) and to the oxygen atoms of the water molecule, the carboxylate group [Cd—O, av. 2.333(8) A] and the N—O, which acts as a bridge [Cd—O, 2.329(8) and 2.371(7) A] in such a way that if all interactions are taken into account, the cadmium atom is hepta-coordinated with a distorted pentagonal bipyramidal geometry. The existence of a hydrogen bond between the water molecule and the carboxylate group helps to achieve a supramolecular self-organization. IR and NMR ( 1 H and 13 C) spectra have also been studied.

SYNTHESIS AND CRYSTAL STRUCTURE OF Δ, L-TRIS-METHYLENEBIS-[DIPHENYLPHOSPHINE OXIDE]NICKEL(II) DIPERCHLORATE METHANOL SOLVATE

Abstract Δ,L-Tris-methylenebis[diphenylphosphine oxid]nickel(II) diperchlorate methanol solvate, Δ, [Ni(bppom)3](ClO4)2· MeOH, was synthesized and its structure determined by single crystal X-ray diffraction at room temperature, and refined to a final R = 0.099 The structure consists of quasi-octahedral, tetragonally distorted, [Ni(bppom)3]2 + cations and perchlorate anions. One methanol molecule of crystallization per formula unit is present. The average Ni-O equatorial and axial distances are 2.075 A and 2.185 A respectively.

Synthesis and Crystal Structure of a Novel Neutral Polymeric Lead(II)-thiosemicarbazonato Complex

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.

Synthesis and Crystal Structure of [Bis(N-oxo-2-acetylpyridine 4N-Methylthiosemicarbazone)zinc(II)] Monohydrate

Abstract The reaction of zinc(II) acetate dihydrate and the tetra-dentate N-Oxo-2-acetylpyridine 4N-methylthiosemicarbazone (H4MLO) produces the novel complex [Zn(C9H11N4OS)2·H2O] (1). The complex crystallizesoin the orthorhombic space group Pbca with a = 15.871(3), b =16.890(3), c = 17.189(3) Å ,V - 4608(1) Å3, Z = 8 . The Zn(II) ion is tetra-coordinated via the thiolate sulfur atom and the azomethine nitrogen atom of two deprotonated ligands. In the solid state, 1 is polymerized via hydrogen bonds with a water molecule of crystallization.

Synthesis and Crystal Structure of a Novel Polymeric Lead(II) Complex with Thiosemicarbazonato and Thiocyanate Ligands

Abstract A novel heptacoordinated thiosemicarbazonato lead(II) complex [Pb(4ML)(SCN)] (4ML = 2-Acetylpyridine-4N-methylthiosemicarbazonato) was synthesized and characterized by conventional methods (IR and elemental analysis) and single-crystal X-ray diffraction. [Pb(4ML)(SCN)] shows an unusual polymeric structure in which the lead atom is hexa-coordinate, the deprotonated thiosemicarbazone both chelates and bridges, and the thiocyanate group acts as bridge between lead(II)-thiosemicarbazonate fragments. There is hydrogen-bonding between the polymeric chains. The complex crystallizes in the triclinic space group P 1̅̅ with a = 7.461(2), b = 9.572(2), c = 11.235(2) Å, α = 66.51(3), β = 84.01(3), γ = 68.75(3)°, V = 685.1(2) Å3, Z = 2.