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Abstract  

Complexes of Cu(II) with substituted o-acetoxy benzoic acids (5-haloaspirines, X-asp) with and without pyridine (py), of composition [Cu2(X-asp)4] and [Cu(X-asp)2(py)2 ] have been synthesized and characterized. Electronic and vibrational spectroscopic data of these complexes are reported. Its thermal behaviour was investigated by thermogravimetry and differential thermal analysis. In all complexes, the haloaspirinate ligands decompose in two or three steps, starting with the break up of the coordinated acetoxy groups. CuO is obtained as the final pyrolysis residue in all cases.

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The complexes of 3,5-dimethoxybenzoates of Co(II), Ni(II) and Cu(II) have been synthesized as hydrated polycrystalline solids and characterized by elemental analysis, IR, FIR and electronic spectroscopy, magnetic studies and X-ray diffraction measurements. They possess colours typical of the M(II) ions: Cu-blue, Ni-green, Co-pink. The carboxylate groups bind as monodentate or a symmetrical, bidentate chelating or bridging ligands. The thermal stabilities were determined in air. When heated they dehydrate to form anhydrous salts which are decomposed to the oxides of respective metals. The magnetic susceptibilities of the complexes were measured over the range 77-300 K and the magnetic moments were calculated. The results reveal the complexes of Ni(II) and Co(II) to be high-spin complexes and that of Cu(II) to form dimer.

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by a Bruker D2 Phaser XRD. Electronic spectra were measured with an Agilent diode array HP 8453 UV–VIS spectrophotometer. The molar magnetic susceptibilities of the complexes were measured on powdered sample at room temperature using a Sherwood

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using Pascal's constant. Electronic spectra were recorded on a Shimadzu 160A UV-visible spectrophotometer using DMF as the solvent blank. The FAB mass spectrum of the heterochelate was recorded at SAIF, CDRI, Lucknow with JEOL SX-102/DA-6000 mass

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Synthesis and structural studies of mixed-ligand complexes

Benzoylacetone andL-proline, 2-pyrrolidone-5-carboxylic acid orL-thioproline

Journal of Thermal Analysis and Calorimetry
Authors: A. Donia, T. Al-Ansi, and M. Othman

Abstract  

Seven mixed-ligand complexes of cobalt(II), nickel(II) and copper(II) containing benzoylacetone andL-proline (HL1), 2-pyrrolidone-5-carboxylic acid (HL2) orL-thioproline (HL3) were prepared and characterized by means of elemental analysis, IR, electronic spectra, magnetic moment measurements and molar conductance. Both HL1 and HL2 coordinate with these metal ions in a neutral zwitterionic form (-NH2-CH-COO), whereas HL3 coordinates as a monobasic chelating agent (O/N). The continuous thermochromism of the nickel(II) complex of HL1 (2) was attributed to a geometry change; it was investigated by DTA, TG, electronic spectra and X-ray powder diffraction techniques.

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Summary  

Six sandwich-type uranium(IV)-polyoxometalates (UIV-POM) were prepared and investigated by FT-IR and UV-VIS spectroscopy. Changes in position and shape of antisymmetric stretching vibration bands in the 640-1000 cm-1 region were identified in all UIV-POM FT-IR spectra. These changes are related to coordination of U(IV) to the trilacunary Keggin units. Visible electronic spectra of aqueous solutions of UIV-POM complexes correspond to uranium 3H4 electronic ground state, having a quasicubic configuration. Presence of electronic transitions were identified by UV spectroscopy of UIV-POM complexes in aqueous solutions.

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The mono- and di-imines of some diaminonaphthalenes were prepared using a solid solid reaction technique. Their structures were studied using elemental analysis, infrared and electronic spectra. The thermal behaviour of the obtained compounds and their solid solid preparation reactions have also been studied. The energies of activation as well as the reaction orders of those reactions were determined.

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Hydrazinium metal glycinates [(N2H5 2M(NH2CH2COO)4] and bis(hydrazine)metal glycinates, [M(NH2CH2COO)2(N2H4)2], whereM=Co, Ni or Zn have been prepared and characterized by chemical analyses, magnetic moments and vibrational and electronic spectra. The thermal behaviour of these compounds has been studied by thermogravimetry and differential thermal analyses. These complexes decompose with high exothermicity giving metal powder as the final residue. The X-ray powder data of each set of complexes show isomorphism among themselves.

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Abstract  

Molybdotellurates [M(H2O)6]3[TeMo6O24], with M=Ni(II) and Co(II), were synthesized and characterized by single-crystal X-ray diffraction for compound 1 and X-ray powder diffraction for compound 2, EDAX, IR, electronic spectra in the solid phase and in solution, and magnetic properties. Thermogravimetry and differential scanning calorimetry of both compounds revealed a loss of 11 water molecules through an endothermal process with ΔH=800 kJ mol−1 for the nickel compound and ΔH=833 kJ mol−1 for the cobalt compound. The residual compounds were characterized by chemical analysis, IR and XPS spectroscopy

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Abstract  

The polyoxotungstate K19[U2KAs4W40O140].42H2O was synthesized and investigated by spectroscopic and magnetic susceptibility measurements. The IR spectrum of the complex contains the nas(U–O)»1133 cm–1 band due to the uranium coordination at {AsW9} units and WO6 binding octahedra. Electronic spectra indicate a 3H4 ground state for the uranium(IV) in a quasicubic configuration. ESR spectra show a small orthorhombic distortion from the cubic symmetry (g x = 2.045, g y = 2.050, g z = 2.085, D = 18.31.10–4 .cm–1, E = 5.99.10–4 .cm–1). The uranium ions are antiferromagnetically coupled for T>200 K (meff = 1.3 mB at room temperature).

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