Metal complexes with Schiff-base ligands - pyridoxal and semicarbazide-based derivatives

The most important results of extensive studies (syntheses, spectral, magnetic, voltammetric and structural characteristics and biological activity) of metal complexes with pyridoxal semi-, thiosemi- and isothiosemicarbazones are reviewed

Cytotoxic activities of new iron(III) and nickel(II) chelates of some S-methyl-thiosemicarbazones on K562 and ECV304 cells

The S-methyl-thiosemicarbazones of the 2- hydroxy-R-benzaldehyde (R= H, 3-OH 3-OCH3 or 4-OCH3) reacted with the corresponding aldehydes in the presence of FeCl3 and NiCl2. New ONNO chelates of iron(III) and nickel (II) with hydroxy- or methoxy-substitued N1,N4-diarylidene-Smethyl- thiosemicarbazones were characterized by means of elemental analysis, conductivity and magnetic measurements, UV-Vis, IR and 1H-NMR spectroscopies. Cytotoxic activities of the compounds were determined using K562 chronic myeloid leukemia and ECV304 human endothelial cell lines by MTT assay. It was determined that monochloro N1-4- methoxysalicylidene-N4-4-methoxysalicylidene-S-methylthiosemicarbazidato- iron(III) complex showed selective anti-leukemic effects in K562 cells while has no effect in ECV304 cells in the 0.53 μg/ml (IC50) concentrations. Also, some methoxy-substitued nickel(II) chelates exhibit high cytotoxic activitiy against both of these cell lines in low concentrations. Cytotoxicity data were evaluated depending on cell lines origin and position of the substituents on aromatic rings

Transition metal complexes with pyrazole-based ligands. XXII. Di-mu-thiocyanato-bis[(3,5-dimethyl-1H-pyrazole-1-carboxamidine-kappa N-2,N )(thiocyanato-kappa N)copper(II)] and a redetermination of bis(3,5-dimethyl-1H-pyrazole-1-carboxamidine-kappa N-2,N )bis(nitrato-kappa O)-copper(II)

The title Cu-II complex, [Cu-2(NCS)(4)(C6H10N4)(2)], represents the first crystal structure of a polynuclear transition metal complex with the 3,5-dimethyl-1H-pyrazole-1-carboxamidine ligand (HL). It is compared with previously reported crystal structures of metal complexes with the same HL ligand. The molecule contains an eight-membered binuclear Cu-2(NCS)(2) ring, which is centrosymmetric and in a chair conformation. The Cu atom has a distorted square-pyramidal geometry with a very elongated Cu-S bond of 2.993 (2) angstrom. The crystal structure redetermination of the bis(3,5-dimethyl-1H-pyrazole-1-carboxamidine-kappa(2)N,N) bis(nitrato-kappa O) copper(II) complex, [Cu(NO3)(2)(C6H10N4)(2)], and analysis of its hydrogen bonds confirm the significance of the NO3 groups in the formation of a three-dimensional hydrogen-bonding network. Both complexes are centrosymmetric, the inversion centre being located at the mid-point of the Cu center dot center dot center dot Cu line in (I) and the Cu atom being located at the inversion centre in (II)

Transition metal complexes with thiosemicarbazide-based ligands. XLIV. Aqua(3-hydroxy-5-hydroxymethyl-2-methylpyridine-4-carboxaldehyde 3-methylisothiosemicarbazone-kappa O-3,N-1,N-4)nitratocopper(II)nitrate

The title complex, [Cu(NO3)(C10H14N4O2S)(H2O)](NO3), is the first metal complex with a Schiff base derived from isothiosemicarbazide and pyridoxal (pyridoxal is 3-hydroxy-5-hydroxymethyl-2-methylpyridine-4-carboxaldehyde). The Cu-II environment is a square pyramid, the equatorial plane of which is formed by the tridentate ONN-coordinated isothiosemicarbazone and one water molecule, while the nitrate ligand is in the apical position. The existence of numerous strong intermolecular hydrogen bonds, and weak C-H...O and C-H...pi interactions, leads to a three-dimensional supramolecular structure

Transition metal complexes with thiosemicarbazide-based ligands. Part L. Synthesis, physicochemical properties and crystal structures of Co(II) complexes with acetone S-methylisothiosemicarbazone

In this paper, we report the synthesis of three novel Co(II) complexes with acetone S-methylisothiosemicarbazone (L), (CH3)(2)C-2 = N-1-(NH)-H-2-C-1(SCH3)=(NH)-H-3. The complexes are characterized by IR spectroscopy and magnetic measurements while in the case of [CoL2Cl]I (1) and [CoLBr2] (2) the crystal structures have been determined by X-ray diffractometry. In both complexes the bidentate L ligand is coordinated in its imido form. In contrast to the other isothiosemicarbazide-based ligands, the molecule of L contains a localized double bond between the carbonyl and isothiosemicarbazide moieties (C-2 = N-1). The coordination polyhedron of I is best described as a distorted trigonal bipyramid. In the aim of a structural comparison, the analysis of similar five-coordinate bis(bidentate)-Co(II) and bis(bidentate)-Co(III) complexes containing two five-membered chelates has been carried out. The results suggest that if there is no steric hindrance between the ligands in the basal plane these complexes prefer a square-pyramidal geometry. The trigonal bipyramidal geometry of I is attributed to the steric interaction of L molecules caused by their favorable planarity. In complex 2 Co(II) exhibits a distorted tetrahedral geometry. The deformation of the coordination polyhedron is mainly attributed to the small bite angle of L. The similar position of the IR absorption bands in the spectra of 1 and 3 suggest their similar structural features. The values of the effective magnetic moments (mu(eff)) per cobalt (II) for the three complexes are slightly higher than the values expected for the spin-only S = 3/2 systems. (c) 2005 Elsevier Ltd. All rights reserved

Transition metal complexes with thiosemicarbazide-based ligands. XLIV. The supramolecular arrangement in the Ni(II) complexes of S-methylisothiosemicarbazide

The reaction of the octahedral complex [Ni(lTSC)(2)(NO3)(2)] (1) with sodium terephthalate yielded the novel octahedral complex [Ni(ITSC)(2)(H2O)(2)](tere) (.) 2H(2)O (2), (ITSC = S-methylisothiosemicarbazide, tere = terephthalate dianion). The X-ray structural analysis of the starting and the final compound showed that they have a centrosymmetric octahedral geometry with the NiN4O2 chromophore. As a result of the non-covalent intermolecular interactions, molecules of both complexes tend to associate into the characteristic 2D blocks separated by S-methyl moieties. In the case of 2, the terephthalate anions, located between the S-methyl groups, enable the transformation of the 2D into 3D supramolecular structure. The similar structural arrangement is also found, in two previously published structures. (C) 2004 Published by Elsevier B.V

Transition metal complexes with pyrazole-derived ligands. XI. [Zn(mu-L)(HL)(OAc)](2) (HL is 4-acetyl-3-amino-5-methylpyrazole)

The title compound, bis(mu-4-acetyl-3-amino-5-methylpyrazolato-N-1 :N-2)bis[(acetato-O)(4-acetyl-3-amino-5-methylpyrazole-N-2)zinc(II)], [Zn-2(C6H8N3O)(2)(C2H3O2)(2)(C6H9N3O)(2)], exists as a centrosymmetric binuclear molecule with two tetrahedrally coordinated Zn atoms bridged by two pyrazolate anions. The geometry of the terminal and bridging pyrazole ligands are slightly different as a consequence of their differing modes of coordination