Elena Bermejo

Spectral and structural studies of iron(III), cobalt(II,III) and nickel(II) complexes of 2-pyridineformamide N(4)-methylthiosemicarbazone

Abstract Reduction of 2-cyanopyridine by sodium in dry methanol in the presence of N(4)-methylthiosemicarbazide produces 2-pyridineformamide N(4)-methylthiosemicarbazone, HAm4M. Complexes with iron(III), cobalt(II,III) and nickel(II) have been prepared and characterized by molar conductivities, magnetic susceptibilities and spectroscopic techniques. In addition, the crystal structures of HAm4M, [Ni(Am4M)(OAc)], [Fe(Am4M)2]ClO4 and [Co(Am4M)2]ClO4 have been solved. Coordination is via the pyridyl nitrogen, imine nitrogen and thione or thiolato sulfur when coordinating as the neutral and anionic ligand, respectively.

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.

Structural and spectral characterization of transition metal complexes of 2-pyridineformamide N(4)-dimethylthiosemicarbazone

Abstract Sodium in dry methanol reduces 2-cyanopyridine in the presence of N(4)-dimethylthiosemicarbazide to produce 2-pyridineformamide N(4)-dimethylthiosemicarbazone, HAm4DM. Complexes with iron(III), cobalt(III), nickel(II), copper(II), palladium(II) and platinum(II) have been prepared and characterized by spectroscopic techniques. In addition, the crystal structures of [Ni(Am4DM)(OAc)], [Ni(Am4DM)(CH3CN)]ClO4, [Cu(Am4DM)(OAc)] and [Pt(Am4DM)(DMSO)]Cl·2H2O are included. Coordination of the anionic thiosemicarbazone ligand is via the pyridyl nitrogen, imine nitrogen and thiolato sulfur atoms. The acetato groups in [Ni(Am4DM)(OAc)] and [Cu(Am4DM)(OAc)] are coordinated as monodentate ligands by one oxygen and the other oxygen interacts intermolecularly with the amide NH2 function of Am4DM. Coordination of the DMSO molecule in [Pt(Am4DM)(DMSO)]Cl·2H2O is through sulfur to give an essentially planar cation.

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.

Structural studies of metal complexes of 2-pyridineformamide N(4)-methylthiosemicarbazone

Abstract Reduction of 2-cyanopyridine by sodium in dry methanol in the presence of N(4)-methylthiosemicarbazide produces 2-pyridineformamide N(4)-methylthiosemicarbazone, HAm4M. In the crystals of [Ni(HAm4M)2](ClO4)2·2H2O, [Zn(Am4M)OAc]2 and [Cd(HAm4M)Cl2]·DMSO the major ligand coordinates via its pyridyl nitrogen, imine nitrogen and sulfur atoms, the last of which forms a thione in the neutral ligand HAm4M and a thiolato group in (Am4M)−. Both the acetato ligands in [Zn(Am4M)OAc]2 are bis-monodentate bridges, which is unique among acetato-bridged binuclear complexes of thiosemicarbazones of this type. As in the complexes of other 2-pyridineformamide thiosemicarbazones, hydrogen bonds play an important role in these compounds. As well as by X-ray diffractometry, the new compounds were characterized by elemental analysis, FAB mass spectrometry and IR spectroscopy; in the case of the nickel(II) complex, by electronic spectroscopy and by molar conductivity and magnetic susceptibility measurements; and in the case of the zinc(II) and cadmium(II) complexes, by NMR spectroscopy (1H, 13C and, for Cd(II), 113Cd).

Syntheses, NMR (1H, 31P) spectroscopy and crystal structures of complexes of copper(I) halides with isatin-3-thiosemicarbazones

Isatin-3-thiosemicarbazones (H2itsc) react with copper(I) bromide or iodide in a 1 : 1 mol ratio in acetonitrile in the presence of two moles of Ph3P to form tetrahedral monomeric complexes of composition [CuX(η1-S-H2itsc)(Ph3P)2], X = Br (1), I (2). These complexes, which have been characterized by single-crystal structure determinations, are unlike the iodo-bridged dinuclear complex of copper(I) iodide of pyrrole-2-carbaldehydethiosemicarbazone (Hptsc), namely [Cu2(μ-I)2(η1-S-Hptsc)2(PPh3)2] (3). In both 1 and 2, the geometry around Cu is distorted tetrahedral with P–Cu–P bond angles being 121.97(3) (1) and 124.09(5)° (2). Proton NMR confirms that thiosemicarbazone coordinates to the Cu atom as a neutral ligand, and 31P NMR shows that there is no dissociation of the complexes in solution; coordination shift values suggest that Ph3P stabilizes the Cu(I) oxidation state.

Structures of 2-pyridineformamide thiosemicarbazone and its complexes with cadmium halides

Reduction of 2-cyanopyridine by sodium in dry methanol in the presence of thiosemicarbazide produces 2-pyridineformamide thiosemicarbazone, HAm4DH. Complexes of HAm4DH with cadmium(II) chloride, bromide and iodide have been prepared and spectroscopically characterized, and crystal structures of [Cd(HAm4DH)Cl2]·DMSO, [Cd(HAm4DH)Br2]·H2O and [Cd(HAm4DH)I2] have been determined by X-ray diffractometry. In each of these complexes neutral HAm4DH coordinates via its pyridyl and imine nitrogens and sulfur, and the cadmium atom is pentacoordinated to the thiosemicarbazone and the two halo ligands. The coordination polyhedra of the three complexes are best described as square pyramidal, with [Cd(HAm4DH)Br2] having the greatest distortion toward a trigonal bipyramid. The hydrogens attached to nitrogens in coordinated HAm4DH form hydrogen bonds with oxygen atoms in solvent molecules and with halo ligands on adjacent molecules.

Spectral and structural studies of metal complexes of 1-phenylglyoxal bis { {N (3) -diethylthiosemicarbazone} }

Abstract Nickel (II) , copper (II) and palladium (II) complexes of 1-phenylglyoxal bis {N (3) -diethylthiosemicarbazone} , H2Pg4DE, have been prepared, studied spectroscopically and their crystal structures solved. H2Pg4DE and the three complexes have been characterized by IR, electronic, 1H NMR (Ni, Pd) and ESR (Cu) spectra. Upon formation of these complexes, loss of the N (2) H hydrogens from both thiosemicarbazone moieties occurs, and the ligands coordinate to the metal centers as dianionic, tetradentate N2S2 ligands. The nickel (II) and copper (II) complexes, [M (Pg4DE) ] , coordinate in the expected 5-5-5-chelate ring system, but [Pd (Pg4DE) ] coordinates with 5-6-4-membered chelate rings. The thiosemicarbazone moiety attached to the phenyl keto carbon in [Pd (Pg4DE) ] forms the 4-membered chelate ring coordinating via N (2) rather than the azomethine nitrogen, N (1) .

Iron(III), cobalt(II,III), copper(II) and zinc(II) complexes of 2-pyridineformamide 3-piperidylthiosemicarbazone

Abstract Reduction of 2-cyanopyridine by sodium in the presence of 3-piperidylthiosemicarbazide produces 2-pyridineformamide 3-piperidylthiosemicarbazone, HAmpip. Complexes with iron(III), cobalt(II,III) copper(II) and zinc(II) have been prepared and characterized by molar conductivities, magnetic susceptibilities and spectroscopic techniques. In addition, the crystal structures of HAmpip, [Fe(Ampip)2]ClO4, [Cu(HAmpip)Cl2]·CH3OH and [Zn(HAmpip)Br2]·C2H6SO have been determined. Coordination is via the pyridyl nitrogen, imine nitrogen and thiolato or thione sulfur when coordinating as the anionic or neutral ligand, respectively.

Spectral and structural studies of mercury(II) complexes of 2- pyridineformamide N(4)-dimethylthiosemicarbazone

Abstract Reaction of 2-pyridineformamide N(4)-dimethylthiosemicarbazone (HAm4DM) with halides of mercury(II) directly afforded complexes of the form [Hg(HAm4DM)X2] (X=Cl, Br or I). In all these new compounds, which were characterized by elemental analysis, IR spectroscopy and 1H, 13C, and, when possible, 199Hg NMR spectroscopy, the ligand coordinates through its sulfur atom and pyridine and azomethine nitrogen atoms, as was confirmed by X-ray diffraction studies in the case of [Hg(HAm4DM)Br2]·DMSO. Ethanolic solutions of [Hg(Am4DM)Cl2] and [Hg(Am4DM)Br2] afforded crystals of [Hg(Am4DM)Cl]2 and [Hg(Am4DM)Br]2, the structures of which were also studied by single-crystal X-ray diffractometry. In these two compounds the anionic ligand, Am4DM−, coordinates to one Hg through pyridine nitrogen, imine nitrogen and thiolato sulfur atoms, the last of which bridges to the other Hg via a bond that is shorter than the chelating HgS bond. Thus all three of the complexes studied by X-ray diffractometry have pentacoordinated Hg centre and in all three cases the coordination polyhedron is closer to a square pyramid than to a trigonal bipyramid.