Synthesis and structure of the dimeric copper(II) complex tetrakis[N-thiazol-2-yl-(4-methylphenyl)sulfonamidate]dicopper(II)

The coordination chemistry of the ligand N-thiazol-2-yl-toluenesulfonamidate towards the copper(II) ion has been investigated using an electrochemical synthesis method. The X-ray structure of this complex was elucidated and is discussed. The compound crystallised in the monoclinic crystal system, P2(1)/c space group with a = 17.3888(9), b = 16.3003(9), c = 18.3679(9) angstrom and beta = 114.3640(10)degrees. Four bidentate sulfathiazolato anions bridge two metal centers in a paddle-wheel fashion, with the nitrogen atoms as donors to give a dimeric species with a Cu center dot center dot center dot Cu distance of 2.7859(5) angstrom.

The mer-[RuCl(3)(dppb)(H(2)O)] complex: A versatile tool for synthesis of Ru(II) compounds

The complex mer-[RuCl(3)(dppb)(H(2)O)] [dppb = 1,4-bis(diphenylphosphino)butane] was used as a precursor in the synthesis of the complexes tc-[RuCl(2)(CO)(2)(dppb)], ct-[RuCl(2)(CO)(2)(dppb)]. cis-[RuCl(2)(dppb)(Cl-bipy)], [RuCl(2Ac4mT)(dppb)] (2Ac4mT = N(4)-meta-tolyl-2-acetylpyridine thiosemicarbazone ion) and trans-[RuCl(2)(dppb)(mang)] (mang = mangiferin or 1,3,6,7-tetrahydroxyxanthone-C2-beta-D-glucoside) complexes. For the synthesis of Run complexes, the Ru(III) atom in mer-[RuCl(3)(dppb)(H(2)O)] may be reduced by H(2)(g), forming the intermediate [Ru(2)Cl(4)(dppb)(2)], or by a ligand (such as H2Ac4mT or mangiferin). The X-ray structures of the cis-[RuCl(2)(dppb)(Cl-bipy)], tc-[RuCl(2)(CO)(2)(dppb)] and [RuCl(2Ac4mT)(dPpb)] complexes were determined. (C) 2010 Elsevier Ltd. All rights reserved.

Metabolic oxidative stress elicited by the copper(II) complex [Cu(isaepy)(2)] triggers apoptosis in SH-SY5Y cells through the induction of the AMP-activated protein kinase/p38(MAPK)/p53 signalling axis: evidence for a combined use with 3-bromopyruvate in neuroblastoma treatment

We have demonstrated previously that the complex bis[(2-oxindol-3-ylimino)-2-(2-aminoethyl)pyridine-N,N`]copper(II), named [Cu(isaepy)(2)], induces AMPK (AMP-activated protein kinase)-dependent/p53-mediated apoptosis in tumour cells by targeting mitochondria. In the present study, we found that p38(MAPK) (p38 mitogen-activated protein kinase) is the molecular link in the phosphorylation cascade connecting AMPK to p53. Transfection of SH-SY5Y cells with a dominant-negative mutant of AMPK resulted in a decrease in apoptosis and a significant reduction in phospho-active p38(MAPK) and p53. Similarly, reverse genetics of p38(MAPK) yielded a reduction in p53 and a decrease in the extent of apoptosis, confirming an exclusive hierarchy of activation that proceeds via AMPK/p38(MAPK)/p53. Fuel supplies counteracted [Cu(isaepy)(2)]-induced apoptosis and AMPK/p38(MAPK)/p53 activation, with glucose being the most effective, suggesting a role for energetic imbalance in [Cu(isaepy)(2)] toxicity. Co-administration of 3BrPA (3-bromopyruvate), a well-known inhibitor of glycolysis, and succinate dehydrogenase, enhanced apoptosis and AMPK/p38(MAPK)/p53 signalling pathway activation. Under these conditions, no toxic effect was observed in SOD (superoxide dismutase)-overexpressing SH-SY5Y cells or in PCNs (primary cortical neurons), which are, conversely, sensitized to the combined treatment with [Cu(isaepy)(2)] and 3BrPA only if grown in low-glucose medium or incubated with the glucose-6-phosphate dehydrogenase inhibitor dehydroepiandrosterone. Overall, the results suggest that NADPH deriving from the pentose phosphate pathway contributes to PCN resistance to [Cu(isaepy)(2)] toxicity and propose its employment in combination with 3BrPA as possible tool for cancer treatment.

The isatin-Schiff base copper(II) complex Cu(isaepy)(2) acts as delocalized lipophilic cation, yields widespread mitochondrial oxidative damage and induces AMP-activated protein kinase-dependent apoptosis

We previously demonstrated that Bis[(2-oxindol-3-ylimino)-2-(2-aminoethyl) pyridine-N, N`] copper(II) [Cu(isaepy)(2)] was an efficient inducer of the apoptotic mitochondrial pathway. Here, we deeply dissect the mechanisms underlying the ability of Cu(isaepy)(2) to cause mitochondriotoxicity. In particular, we demonstrate that Cu(isaepy)(2) increases NADH-dependent oxygen consumption of isolated mitochondria and that this phenomenon is associated with oxy-radical production and insensitive to adenosine diphosphate. These data indicate that Cu(isaepy)(2) behaves as an uncoupler and this property is also confirmed in cell systems. Particularly, SH-SY5Y cells show: (i) an early loss of mitochondrial transmembrane potential; (ii) a decrease in the expression levels of respiratory complex components and (iii) a significant adenosine triphosphate (ATP) decrement. The causative energetic impairment mediated by Cu(isaepy)(2) in apoptosis is confirmed by experiments carried out with rho(0) cells, or by glucose supplementation, where cell death is significantly inhibited. Moreover, gastric and cervix carcinoma AGS and HeLa cells, which rely most of their ATP production on oxidative phosphorylation, show a marked sensitivity toward Cu(isaepy)(2). Adenosine monophosphate-activated protein kinase (AMPK), which is activated by events increasing the adenosine monophosphate: ATP ratio, is deeply involved in the apoptotic process because the overexpression of its dominant/negative form completely abolishes cell death. Upon glucose supplementation, AMPK is not activated, confirming its role as fuel-sensing enzyme that positively responds to Cu(isaepy)(2)-mediated energetic impairment by committing cells to apoptosis. Overall, data obtained indicate that Cu(isaepy)(2) behaves as delocalized lipophilic cation and induces mitochondrial-sited reactive oxygen species production. This event results in mitochondrial dysfunction and ATP decrease, which in turn triggers AMPK-dependent apoptosis.

Synthesis and characterization of TiO2 chemically modified by Pd(II) 2-aminothiazole complex for the photocatalytic degradation of phenol

An investigation was made into the photocatalytic activity of in situ synthesized TiO2 chemically modified by Pd(II) 2-aminothiazole complex for phenol degradation at different pH values. At longer reaction times, the bare titania presented far poorer pbotoactivity than the modified catalysts in the entire range of pH studied. The catalyst complexed with Pd(II) was more efficient than the metal-free Pd, irrespective of pH and reaction time, suggesting that metal plays an important role. A cooperative mechanism is proposed, involving the possible photoactivation of both TiO2 and sensitizer. (C) 2007 Elsevier B.V. All rights reserved.

The sensitization of the ligand-field state of the hexaammineruthenium(II) complex ion by organic compounds

The sensitized photolysis of [Ru(NH3)(6)](2+) by the organic dye rhodamine B and biacetyl was studied under conditions in which only the sensitizer absorbs. The reaction products resulting from ammonia aquation and Ru(II) to Ru(III) oxidation are the same for direct and sensitized photolysis. The energy transfer rate constant, calculated from the fluorescence quenching of rhodamine B, is similar to that estimated from the limiting quantum yield of the photosensitized photoaquation of the complex. Both reactions originate from a common reactive low-lying ligand-field (LF) state, which is also responsible for the direct photolysis reactions. This state, which leads directly to photoaquation, seems to have a certain charge transfer to solvent (CTTS) character, which is responsible for the photo-oxidation products. Sensitization is effective with rhodamine B (17 450 cm(-1)) and biacetyl (19 000 cm(-1)), whereas no reaction is observed with neutral red (16 900 cm(-1)). These results show that the excited state responsible for the photochemical reactions lies in the energy range between 16 900 cm(-1) and 17 700 cm(-1) and possesses spin-orbit character.

A solid nickel(II) complex with methionine sulfoxide

Solid Ni(C(5)H(10)NO(3)S)(2) . 2H(2)O complex was prepared and characterized. Electronic absorption spectrum shows an octahedral geometry for the complex. Infrared spectroscopy analysis shows that the metal atom is coordinated to the ligand through (COO(-)) and (S = O) groups. Thermal analysis confirmed the composition of the complex and suggests that the water molecules are not coordinated to the metal ion. The complex shows extremely high solubility in water. (C) 2000 Elsevier B.V. S.A. All rights reserved.

Synthesis, spectroscopic characterization and biological analysis of a new palladium(II) complex with methionine sulfoxide

A new palladium(II) complex with methionine sulfoxide was synthesized and characterized by a set of chemical and spectroscopic techniques. Elemental and mass spectrometry analyses of the solid complex fit to the composition [Pd(C5H10NO3S)(2)]center dot H2O. C-13 NMR, [H-1-N-15] NMR and infrared spectra indicate coordination of the amino acid to Pd(II) through the carboxylate and amino groups in a square planar geometry. The complex is soluble in water.Biological activity was evaluated by cytotoxic analysis using HeLa cells. Determination of cell death was assessed using a tetrazolium salt colorimetric assay, which reflects the cells viability. After incubation for 48 h, 20% of cell death was achieved at a concentration of 200 mu mol L-1 of the complex. (c) 2006 Elsevier B.V. All rights reserved.

Crystal structure and infrared analysis of a new trinuclear platinum(II) complex with L-cysteine

A new trinuclear platinum(II) complex with cysteine of composition [Pt(C3H6NO2S)Cl](3)center dot(C2H6SO)(3) was obtained and structurally characterized by X-ray diffraction and infrared analysis. The compound crystallizes in the trigonal system, space group R3, and is described in a hexagonal cell with a=17.739(1), c=9.531(1) and Z=3. Cysteine is coordinated to Pt(II) through the nitrogen and sulphur atoms. Each cysteine sulphur bridges between two metal atoms. A square planar coordination sphere of platinum is completed by a chlorine atom. The complex is soluble in dimethyl sulfoxide.

Cycloaddition reaction of the azido-bridged cyclometallated complex [Pd(dmba)N-3](2) with CS2. Crystal and molecular structure of DI(mu, N,S-1,2,3,4-thiatriazole-5-thiolate) bis[(N,N-dimethylbenzyl-amine-C-2,N)palladium(II)]

The 1,3-dipolar cycloaddition of carbon disulfide to the coordinated azide in the cyclometallated compound [Pd(dmba)(N-3)](2) (1), dmba = N,N-dimethylbenzylamine, was investigated. The compound obtained di(mu, N,S-1,2,3,4-thiatriazole-5-thiolate)-bis[(N,N-dimethylbenzylamine-C-2,N)palladium(II)] (2), was characterized by IR spectroscopy and X-ray diffraction. Complex (2) is dimeric with the two [Pd(N,N-dimethylbenzylamine)] moieties being connected by the two vicinal bridging N,S-1,2,3,4-thiatriazole-5-thiolate anions in a square-planar coordination for the palladium atoms.

X-ray powder diffraction analysis of a new palladium(II) amino acid complex

Powder X-ray diffraction data for a new palladium(II) amino acid complex, of composition PdC12H2ON2O4S2, are presented in this paper. Orthorhombic cell parameters are: a = 10.740 angstrom, b = 19.999 angstrom, and c = 5.2470 angstrom. (c) 2004 International Centre for Diffraction Data.

Synthesis, structure and redox properties of an unexpected trinuclear copper(II) complex with aspartame: [Cu(apm)(2)Cu(mu-N,O : O '-apm)(2)(H2O)Cu(apm)(2)(H2O)]center dot 5H(2)O

Structural, magnetic and spectroscopic data of a new trinuclear copper(II) complex with the ligand aspartame (apm) are described. [Cu(apm)(2)CU(mu-N,O:O'-apm)(2)(H2O)Cu(apm)(2)(H2O)]-5H(2)O crystallizes in the triclinic system, space group P1 (#1) with a = 7.3300(1) angstrom, b = 15.6840(1) angstrom, c = 21.5280(1) angstrom, alpha = 93.02(1)degrees, beta = 93.21 (1)degrees, gamma = 92.66(1)degrees and Z = 1. Aspartame coordinates to Cu(II) through the carboxylate and beta-amino groups. The carboxylate groups of the two central ligands act as bidentate bridges in a syn-anti conformation while the carboxylate groups of the four peripheral ligands are monodentate in a syn conformation. The central copper ion is in a distorted square pyramidal geometry with the apical position being occupied by one oxygen atom of the water molecule. The two terminal copper(II) atoms are coordinated to the ligands in the same position but their coordination sphere differs from each other due to the fact that one copper atom has a water molecule in an apical position leading to an octahedral coordination sphere while the other copper atom is exclusively coordinated to aspartame ligands forming a distorted square pyramidal coordination sphere. Thermal analysis is consistent with the X-ray structure. EPR spectra and CV curves indicate a rupture of the trinuclear framework when this complex is dissolved in ethanol or DMF, forming a mononuclear species, with a tetragonal structure. (c) 2005 Elsevier B.V. All rights reserved.

Thermal behaviour of Tin(II) complex with 8-hydroxyquinolinate in the solid state

Tin(II) complexes with 8-hydroxyquinolinate in solid state have been obtained by adding aqueous ammonium to a solution containing stannous chloride and 8-hydroxiquinoline in medium of HCl and acetone up to pH 5 and 9, respectively. The products obtained show the same composition, Sn(C9H6ON)(2); however there are some differences regarding both the thermal behaviour in an oxidant atmosphere and morphology. These products were characterised by elemental and complexometric analysis, TG and DTA curves, infrared and X-ray diffractometry. TG curves show, above 448 K, the partial oxidation on air atmosphere of Sn(II) complexes to Sn(IV) complexes, SnO(C9H6ON)(2). This behaviour does not depend only on pH in which the compounds were obtained but also on the heating rate in TG curves. Sn(II) complexes volatilise almost completely on nitrogen atmosphere and partially on air atmosphere depending on the oxidation degree of the compound.

Synthesis, characterization and initial biological studies of a new platinum(II) complex with deoxyalliin

A new platinum(II) complex with deoxyalliin was synthesized and characterized by chemical and spectroscopic techniques. Elemental and mass spectrometry analyses of the solid complex fit to the composition [Pt(C6H11NO2S)Cl-2] center dot H2O. C-13 NMR, N-15 NMR and infrared spectra of the complex are consistent with coordination of deoxyalliin to Pt( II) through the nitrogen and sulfur atoms forming a square-planar geometry. The complex is soluble in dimethylsulfoxide. Biological analysis for evaluation of a potential cytotoxic effect of the complex was performed using HeLa cells, a human cervix adenocarcinoma-derived cell line. The results were compared with those of a palladium( II) complex previously described.