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.3007 0.004585 −30.98 −30.46 Table 3 The thermodynamic parameters of mixed-ligand complex formation in the systems

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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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If heated to around 270° in argon, [Ni(HSal)2] (H2Sal=salicylic acid) gives off gaseous H2Sal and forms [NiSal], which reacts with monoprotic ligands HL (e.g. 8-hydroxyquinoline) to form mixed-ligand complexes [NiHSalL], or with diprotic ligands H2L' (e.g. quadratic acid) to form dinuclear complexes [HSalNiL'NiHSal].

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Abstract  

The solvent extraction of europium(III) with di-n-butylphosphoric {HDBP} and di-(2-ethylhexyl)phosphoric {HDEHP} acids in 3-methyl-1-butanol from 0.1 and 1.0M perchlorate medium {Na(H)ClO4} was studied at pH 1–3. It was found that the composition of the species extracted into the organic phase depended on the concentration of perchlorate anion. In 0.1M Na(H)ClO4 solutions, simple chelates Eu(DBP)3 or Eu(DEHP)3 are extracted while mixed ligand complexes Eu(DBP)2ClO4 or Eu(DEHP)2ClO4 are also extracted from 1.0M Na(H)ClO4 solutions. Compared to the extractions from perchlorate solutions, no such change in the extraction mechanism has been observed in chloride solutions containing up to 1.0M Cl. The extraction of europium(III) with these extractants into toluene from 0.1M perchlorate or chloride media was studied as well. The extraction species found were identical with those reported in the literature, i.e. {Eu[H(DBP)2]3, Eu[H(DEHP)2]3}. The extraction equilibrium constants were calculated for all complexes.

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Abstract  

The mixed-ligand complex formation in the system Cu2+−Edta4−−(CH2)6(NH2)2 (L), where L is hexamethylenediamine has been calorimetrically, pH-potentiometrically and spectrophotometrically studied in aqueous solution at 298.15 K and the ionic strength of I = 0.5 (KNO3). The thermodynamic parameters of formation of the CuEdtaL2−, CuEdtaHL (CuEdta)2L4− and (CuEdta)2En4− complexes have been determined. The most probable coordination mode for the complexone and the ancillary ligand in the mixed-ligand complexes was discussed.

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Abstract  

Parent and mixed-ligand cobalt(II) complexes of different compositions were prepared with water, sulfate ion and 1,2-ethanediol as ligands. The magnetic susceptibility data, the IR spectra and the thermoanalytical curves of the complexes were recorded. Oxygen atoms bound by one or two coordinate bonds to the metal ion, or by hydrogen-bonds were observed in the crystals pace.

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Parent and mixed-ligand cobalt(II) complexes of different compositions were prepared with water, sulfate ion and 1,2-ethanediol as ligands. The magnetic susceptibility data, the IR spectra and the thermoanalytical curves of the complexes were recorded. Oxygen atoms bound by one or two coordinate bonds to the metal ion, or by hydrogen-bonds were observed in the crystals pace.

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Abstract  

This paper reports the isolation and characterisation of mixed ligand complexes of the types Ba[M(Ox)2glydtc], [M2′(Ox)4glydtc], [M2(QA)2glydtc] and [M2′(QA)4glydtc] (where glydtc=glycinyldithiocarbamate; HOx=8-hydroxyqinoline;HQA=p-methyl-5-phenylazo-8-hydroxyquinoline and M=Co(II),Ni(II) or Cu(II); M′=Fe(III) or Cr(III). The structures for the complexes have been elucidated on the basis of elemental analysis, electronic, IR and mass spectroscopy. Electronic spectral data for the complexes were in accordance with an octahedral environment around the central metal ions in all metal chelates except for [Co2(QA)2glydtc] and [Ni2(QA)2glydtc] where the structure around Co(II) and Ni(II) may be tetrahedral. The complexes were proposed to be dimeric except those of Ba[M(Ox)2glydtc]. A study of the thermal decomposition of the complexes has also been carried out. For Ba[M(Ox)2glydtc], elimination of carbon dioxide was observed. However, evolution of nitrogen and formation of tolyl radicals occur for [M2(QA)2glydtc] and [M2′(QA)4glydtc]. Kinetic parameters for the various decomposition stages were calculated using the Coats–Redfern and Horowitz–Metzgerequations.

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Abstract  

Ten mixed ligand complexes of the type [M(X-QA)(aa)] and [Ni(X-QA)2(Haa)(H2O)],where X-HQA=5-arylazo-8-hydroxyquinoline derivatives, M=Co(II) orCu(II) and Haa=glycine (gly), alanine (ala) or methionine (met), have been prepared. The complexes have been characterized by elemental analysis, IR and electron spectra and thermal analysis. A tetrahedral structure has been proposed for the cobalt(II) and copper(II) complexes with bidentate coordination of amino acids. The nickel(II) complexes have been assigned an octahedral structure with the amino acids acting as monodentate ligands. The thermal behaviour of the complexes has been studied before and after γ-irradiation.

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