Transition metal complexes with pyrazole-based ligands. Part 29. Reactions of zinc(II) and mercury(II) thiocyanate with 4-acetyl-3-amino-5-methylpyrazole

The work is concerned with the crystal and molecular structures of zinc(II) and mercury(II) complexes with 4-acetyl-3-amino-5-methylpyrazole (aamp) of the coordination formulae [Zn(NCS)(2)(aaMP)(2)] and (HaaMP)(2)[Hg(SCN)(4)]. The zinc(II) complex was obtained by the reaction of a warm methanolic solution of aamp with a mixture of zinc(II) nitrate and ammonium thiocyanate, whereas the mercury(II) complex was prepared by the reaction of a warm methanolic solution of aamp and a warm, slightly acidified aqueous solution of [Hg(SCN)(4)](2-). Both complexes have a tetrahedral geometry, which in the case of zinc complex is formed by monodentate coordination of two aamp molecules and two isothiocyanate groups. The Zn(II) and Hg(II) atoms have significantly deformed coordination geometry. In both crystal structures the pyrazole derivative has a planar form, probably stabilized by an intramolecular N-H center dot center dot center dot O hydrogen bond. Apart from the X-ray structural analysis, the isolated complexes were characterized by elemental analysis, IR spectroscopy, conductometric measurements and thermal analysis

Synthesis and Characterization of Stable Aqueous Ceria Sols

Stable colloidal aqueous dispersions (sols) of cerium (IV) oxide of uniform size distribution were obtained by forced hydrolysis of cerium (IV) ions in the presence of diluted sulfuric or nitric acids. Synthesis of ceria sols was carried out using two commercially available precursors: Ce(SO4)(2) center dot 4H(2)O salt and 0.25 mol/L Ce(NO3)(4) aqueous solution. The precursors were dissolved in different concentrations of diluted sulfuric or nitric acid. After aging for various periods of time (2-24 h), the sols were cooled at room temperature. Sulfate and nitrate ions were removed from the sols particles by ultrafiltration. Characterization of the synthesized ceria sols has been made by X-ray diffraction, nitrogen adsorption/desorption, and DSC-TGA thermal analysis, as well as IR spectroscopy. Particle sizes, measured using a Zetasizer Nano equipped with a MPT-2 Autotitrator, range from 20 to 600 nm

Preparation and Thermal Stability of Elastomers Based on Irregular Poly(urethane-isocyanurate) Networks

The objective of this study was to investigate the thermal stability of poly(urethane-isocyanurate) networks with increasing amount of dangling chains. In order to improve thermal stability of elastomeric materials, networks were prepared by adding some heat resistant isocyanurate rings as a junction points by catalytic cyclotrimerisation of telechelic diisocyanates. The thermal degradation kinetics of samples has been studied by means of high-resolution thermal analyzer SDT Q600 TA Instruments, under nitrogen atmosphere. The activation energy for the two step reactions of thermal decomposition of different species was calculated and compared

Mechanism of complex formation between [AuCl4](-) and L-methionine

The kinetics of the reaction between the tetrachloroaurate(III) ion and L-methionine (L-Met) (0.1 M HClO4, pH 1.0-2.5) have been studied spectrophotometrically using a stopped-flow technique at different temperatures. Initially, the fast substitution reaction was ascribed to the formation of the short-lived square-planar Au(III)-(L-Met) that was followed by the replacement of a Cl- ligand and a subsequent, slower reduction to Au(I)-(L-Met). This is an intermolecular process, involving attack on the [AuCl4](-) Complex by an outer-sphere L-methionine. The activation parameters (Delta H-not equal and Delta S-not equal) for substitution and reduction were determined. IR spectroscopy indicates that L-methionine acts as a bidentate ligand, most likely coordinating via the S and N atoms, while H-1 and C-13 NMR data indicate methionine sulfoxide as the final product. Finally, the components of the reaction were treated thermally in order to investigate the solid phase synthesis of the resulting complex. (C) 2008 Elsevier Ltd. All rights reserved

Reaction of copper(II) with 1-carboxamide-3,5-dimethylpyrazole, 1-carboxamidine-3,5-dimethylpyrazole, 4-acetyl-3-amino-5-methylpyrazole and 5-amino-4-carboxamide-1-phenylpyrazole

International audienceComplex formation of copper(II) bromide and acetate with 1-carboxamide-3,5-dimethylpyrazole (HL3) and copper(II) bromide with 5-amino-4-carboxamide-1-phenylpyrazole (L2), 4-acetyl-3-amino-5-methylpyrazole (HL4) and 1-carboxamidine-3,5-dimethylpyrazole (HL5), was studied. The obtained compounds, CuBr2(L2)2, Cu(L 3)2, CuBr2(HL4)2, CuBr2(HL5)2 and [CuBr(HL1)(L 3)]2 (HL1 denotes the 3,5-dimethylpyrazole), are characterized by elemental analysis, FT-IR spectrometry, molar conductivity, TG-MS and DSC. The X-ray structure of [CuBr(HL1)(L 3)]2 and Cu(L3)2 is discussed. For [CuBr(HL1)(L3)]2 a dimeric penta-co-ordinated structure has been found; the co-ordination around the metal in Cu(L 3)2 is trans-square planar. To CuBr2(L 2)2 and CuBr2(HL4)2 a nearly tetrahedral, while for CuBr2(HL5)2 an octahedral geometry may be assumed. It means that the geometry of the compounds in the first place depends on the ligand substituents. The course of the complex formation reaction is anion-dependent and may be explained on the basis of Pearson's theory, taking into account the steric factors. A low stability intermediate formation was observed in the thermal decomposition of Cu(L 3)2

Pyrazole-type complexes with Ni(II) and Cu(II) Solvent exchange reactions in coordination compounds

New nickel(II) and copper(II) coordination compounds were synthesized by the reaction of N-(benzyloxycarbonyl)-1H-pyrazole-1-carboxamidine ligand (HL) with Ni(II) and Cu(II) acetate in methanolic solution. The crystal and molecular structures of the complexes as well as those of the ligand were determined by single-crystal X-ray structure analysis. The octahedral surrounding around the metal centers in the isostructural complexes [ML2(MeOH)(2)], M = Ni(II), Cu(II), MeOH = methanol, is established by the bidentate coordination of two ligand molecules through the pyrazole nitrogen and the deprotonated nitrogen atom of the carboxamidine group along with the oxygen atoms from two MeOH molecules. Despite that the molecular structure of the complexes was determined by X-ray structure analysis, in the FT-IR spectra of the compounds the characteristic bands for MeOH were missing. By coupled TG-MS measurements, it was found that compounds during the transport and storage exchanged MeOH by water molecules. The amount of the water was calculated on the basis of thermogravimetric data. The antifungal activity of the compounds was tested against fungi Ph. viticola and B. dothidea and compared to that of a commercial fungicide. Depending on the fungi and on the structure, the compounds showed different, but somewhat lower activity than the commercial fungicide

Coordination compounds of a hydrazone derivative with Co(III), Ni(II), Cu(II) and Zn(II): synthesis, characterization, reactivity assessment and biological evaluation

A new hydrazone-type ligand with a five N-donor set and its coordination compounds with Co(III), Ni(II), Cu(II) and Zn(II) metal centres were synthesized. The crystal and molecular structure of the Co(III) complex was determined by X-ray structural analysis. All the compounds were characterized by elemental analysis, molar conductivity and FT-IR spectral data. The cobalt(III) compound is a neutral binuclear complex formed by coordination of two, doubly deprotonated ligand anions as bridges between the Co(III) centres. The metal centres are additionally connected by a peroxido bridge, which was observed for the first time in Co(III) complexes with similar ligands. The other coordination compounds are mononuclear complexes wherein only one doubly deprotonated ligand is coordinated to the central ion in a tetradentate fashion. The structures were theoretically investigated employing density functional theory (DFT) calculations with B3LYP exchange-correlation functional and LACV3P+(d,p) basis sets for the coordination compounds and 6-31+G(d,p) basis set for the ligand. Molecular electrostatic potential (MEP) and average local ionization energy (ALIE) surfaces were calculated to study the reactive properties of the compounds. The thermal behaviour of the compounds was determined by simultaneous thermogravimetric-differential scanning calorimetric (TG-DSC) measurements and the results were correlated to the proposed structures and to calculated MEP/ALIE surfaces. The compounds were tested in vitro for antiproliferative effects on parental (L5178Y) mouse T-cell lymphoma cells, on L5178Y transfected with pHa ABCB1/A retrovirus and for reversal of multidrug resistance (MDR) in tumor cells by flow cytometry. The preliminary measurements showed that the cobalt(III) compound was an effective inhibitor of the ABC transporter PGP drug efflux pump. The ligand was somewhat less effective, the zinc complex had a moderate inhibition activity, whereas the nickel(II) and copper(II) compounds were inactive.6th EuCheMS Conference on Nitrogen Ligands, Sep, 2015, Beaune, Franc