Studies on the thermal decomposition of salicylhydroxamic acid and its metal complexes with Ni(II), Co(II), Fe(II), Mn(II) and Zn(II)

The thermal decomposition of salicylhydroxamic acid and its metal complexes with Ni(II), Co(II), Fe(II), Mn(II) and Zn(II) has been studied by TG, DTG, DTA and IR spectroscopy. All the compounds investigated decompose to yield intermediate N-hydroxylactams.Decomposition schemes have been proposed and reaction enthalpies and kinetic parameters have been calculated.     

Thermal decomposition of Co(II), Ni(II), Cu(II) and Zn(II) hippurates

The hippurates of Co(II), Ni(II), Cu(II) and Zn(II) were isolated from the solution, their quantitative composition and the way of coordination of metal — ligand were determined and the conditions and products of thermal decomposition during heating in air atmosphere up to 1273 K were studied. The complexes of Ni(II), Cu(II) and Zn(II) heated lose some water molecules and then decompose to MO. The hippurate of Co(II) heated loses some water molecules and then decomposes to CoO with intermediate formation Co₃O₄.

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Zusammenfassung Aus Lösung wurden die Co(II)-, Ni(II)-, Cu(II)- und Zn(II)-Salze der Hippursäure gewonnen, ihre quantitative Zusammensetzung sowie die Art der Koordination der Metall-Ligandenbindung bestimmt. Weiterhin wurden die Bedingungen und Produkte der thermischen Zersetzung beim Erhitzen in einer Luftatmosphäre bis 1273 K untersucht. Die Komplexe von Ni(II), Cu(II) und Zn(II) verlieren beim Erhitzen ein paar Moleküle Wasser und zersetzen sich anschlieend zu MO. Co(II)-hippurat gibt beim Erhitzen einige Moleküle Wasser ab und zersetzt sich dann über die Zwischenstufe Co₃O₄ zu CoO.

     

Structural and thermal decomposition characteristics of mixed-ligand complexes of Cu(II), Ni(II), Co(II) and Zn(II)

Mixed-ligand complexes of Cu(II), Ni(II), Co(II) and Zn(II) with 8-hydroxyquinoline and thiophene-2-carboxylic acid as two different ligands, have been isolated in pure state. The formation of these complexes has been inferred potentiometrically. The isolated complexes have been characterized by their elemental analyses, IR and electronic spectra, conductivity and magnetic measurements. Solid state dehydration of the hydrated complexes and subsequent decomposition of the anhydrous complexes have been studied by simultaneous DTA and TG techniques. The thermal stability order of the hydrated compounds is Cu>Co>Ni>Zn, but in the decomposition process the trend observed is Co>Zn>Ni>Cu. Some parameters like activation energy and order of reaction for each process have been computed.     

Thermal decompositions of formates. Part IV. Thermal dehydrations of Mg(II), Mn(II), Fe(II), Co(II), Ni(II), Cu(II), Zn(II) and Cd(II) formate dihydrates

The thermal dehydrations of formate dihydrates of Mg(II), Mn(II), Fe(II), Co(II), Ni(II), Cu(II), Zn(II) and Cd(II) were studied by means of thermogravimetry, differential thermal analysis and differential scanning calorimetry in air.The reaction orders of dehydration obtained by the dynamic and the static methods were found to be 2/3 for all the salts examined, which indicated that the rate of dehydration was controlled by a chemical process at a phase boundary. This was confirmed by microscopic observation.The values of activation energy, frequency factor and the enthalpy change of dehydration for all salts examined, were 21–30 kcal mole^?1, 10¹⁰-10¹² sec^?1 and 28–31 kcal mole^?1, respectively.The temperature at which the dehydration occurred was regarded as a measure of the strength of the metalOH₂ bond, and this temperature increased with increasing the reciprocal of the radius of the metallic ion.     

Preparation,IR spectra and thermal decomposition of malatoaquo complexes of Mn(II), Co(II), Ni(II) and Cu(II)

Reaction of malate ion with Mn(II), Co(II) and Ni(II) gave malatotriaquo complexes of these ions, while Cu(II) gave the malatoaquo complex. The structures of these complexes were predicted from elemental analysis and IR spectra. Thermal decomposition of the complexes using TG, DTG and DTA gave supporting evidence for the predicted structures. A correlation between the thermal stability of these complexes and the covalency of the MO bond was made.     

Spectral,thermal and magnetic investigations of Mn(II), Co(II), Ni(II), Cu(II), Zn(II) and Cd(II) 4-methylphthalates

Conditions for the preparation of Mn(II), Co(II), Ni(II), Cu(II), Zn(II) and Cd(II) 4-methylphthalates were investigated and their composition, solubility in water at 295 K and magnetic moments were determined. IR spectra and powder diffraction patterns of the complexes prepared with molar ratio of metal to organic ligand of 1.0:1.0 and general formula: M [ CH₃C₆H₃(CO₂)₂]·nH₂o (n=1-3) were recorded and their decomposition in air were studied. During heating the hydrated complexes are dehydrated in one (Mn, Co, Ni, Zn, Cd) or two steps (Cu) and next the anhydrous complexes decompose to oxides directly (Cu, Zn), with intermediate formation of carbonates (Mn, Cd), oxocarbonates (Ni) or carbonate and free metal (Co). The carboxylate groups in the complexes studied are mono- and bidentate (Co, Ni), bidentate chelating and bridging (Zn) or bidentate chelating (Mn, Cu, Cd). The magnetic moments for paramagnetic complexes of Mn(II), Co(II), Ni(II) and Cu(II) attain values 5.92, 5.05, 3.36 and 1.96 M.B., respectively. This revised version was published online in July 2006 with corrections to the Cover Date.     

Thermal decomposition kinetics of Co(II), Ni(II), Cu(II) and Zn(II) complexes of dihydrazinium ethylenediamine-tetraacetate

Hydrazinium ethylenediaminetetraacetatometalate complexes of the type, N₂H₅ [M(Hedta)·H₂O] were subjected to systematic TG/DTG analysis. The decomposition process consists of three stages. Kinetic parameters were evaluated for each of these stages using the Coats-Redfern equation.     

Chelation behaviour of nitroso- pyrazolones with Mn(II), Co(II), Ni(II), Cu(II) AND Zn(II)

Infrared (IR), nuclear magnetic resonance (NMR), thermogravimetric analysis (TG), derivative thermogravimetric analysis (DTG), differential thermal analysis (DTA) and molar conductivity studies have been carried out on the chelates of Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) with 3-methyl- and 3-phenyl-4-nitroso-5-pyrazolones. The solid chelates were synthesized, separated, analyzed and their structures were elucidated. The data obtained show that almost all of the prepared chelates contain water molecules in their coordination sphere. The initial stage in the thermal decomposition process of these chelates shows the presence of water molecule, the second denotes to the intermediate products. The final decomposition products were found to be the respective metal oxides. The NMR spectrum of 3-methyl-4-nitroso-5-pyrazolone ligand shows the existence of the oxime rather than the nitroso form. 3-phenyl-4-nitroso-5-pyrazolone acts as a neutral bidentate ligand whereas 3-methyl-4-nitroso-5-pyrazolone acts as monobasic bidentate ligand bonded to the metal ions through the two oxygen atoms of the carbonyl and nitroso groups. The solid chelates prepared behave as non-electrolytes in DMF solution. The coordination numbers of the obtained chelates using 3-methyl-4-nitroso-5-pyrazolone are four on applying the mole ratio 1:1 and six on using 1:2 mole ratio. In case of using the ligand 3-phenyl-4-nitroso-5-pyrazolone the coordination number is six in both cases. This revised version was published online in August 2006 with corrections to the Cover Date.     

Synthesis, spectral and thermal studies of Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) complex dyes based on hydroxyquinoline moiety

A series of Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) complexes of azo-compounds containing hydroxyl quinoline moiety have been synthesized and characterized by elemental analysis, molar conductance, magnetic moments, IR, electronic and ESR spectral studies. The results revealed the formation of 1:1 and 1:2 (L:M) complexes. The molar conductance data reveal that the chelates are nonelectrolyte. IR spectra indicate that the azodyes behave as monobasic bidentate or dibasic tetradentate ligands through phenolate or carboxy oxygen, azo N for 1:1 (L:M) complexes beside phenolate oxygen and quinoline N atoms for 1:2 (L:M) complexes. The thermal analyses (TG and DTA) as well as the solid electrical conductivity measurements are also studied. The molecular parameters of the ligands and their metal complexes have been calculated.     

Synthesis and characterization of Fe(III), Co(II), Ni(II), Cu(II) and Zn(II) complexes with N-salicydene-o-hydroxymethyleneaniline

The new Fe(III), Co(II), Ni(II), Cu(II) and Zn(II) complexes with tridentate Schiff base, the product of condensation of o-aminobenzyl alcohol with salicylaldehyde have been synthesized and characterized by elemental analysis, IR, electronic, EPR and Mössbauer spectra, thermal analysis, magnetic susceptibility and molecular weight measurements. Dimeric or polymeric structures for the investigated complexes were proposed. The interaction of the cobalt complex with dioxygen is also described.     

Structural and thermal analysis of bis-(5-sulphosalicylato)-diaquo complexes of VO(II), Cu(II), Ni(II), Co(II), Fe(II) and Mn(II)

The reactions of the 5-sulphosalicylate anion with VO(II), Cu(II), Ni(II), Co(II), Fe(II) and Mn(II) gave bis-(5-sulphosalicylato)-diaquo complexes. The structures of these complexes were predicted from elemental analyses and IR spectra. Their decompositions were studied by TG, DTG and DTA. Decomposition occurred in two steps: elimination of two water molecules, followed by decomposition of the dehydrated complex to give metal oxide as end-product. The thermal stability sequence for the complexes wasVO(II) > Cu(II) > Co(II) Ni(II) Fe(II) > Mn(II), which is in accordance with the covalency sequence for the M-O bond.

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Zusammenfassung Die Reaktionen des 5-Sulphosalicylat-Anions mit VO(II), Cu(II), Ni(II), Co(II), Fe(II) und Mn(II) ergaben Bis-(5-sulphosalicylato)-diaquo-Komplexe. Die Strukturen dieser Komplexe wurden durch Elementaranalyse und IR-Spektren bestätigt. Die Zersetzung der Komplexe wurde mittels TG, DTG und DTA untersucht. Die Zersetzung verläuft in zwei Schritten: Eliminierung der zwei Wassermoleküle, gefolgt von der das Metalloxid als Endprodukt ergebenden Zersetzung des dehydratisierten Komplexes. Die Thermische Stabilität der Komplexe nimmt in der Reihenfolge VO(II) > Cu(II) > Co(II) Ni(II) Fe(II) > Mn(II) ab, womit die gleiche Reihenfolge wie für die Kovalenz der M-O-Bindung festgestellt wurde.

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5- - , , , , -(5- )- . . , : : . VO > u > Ni Fe > n, -.

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The authors are sincerely grateful to the late Dr. M. D. Karkhanawala (then Head, Chemistry Division, BARC, India) for providing facilities, and to the U. G. C. (India) for research fellowships to the authors (BDH and SMA).     

Formation of Fe(II), Co(II), Ni(II), Cu(II), Zn(II), Ag(I) and Cd(II) hexacyanocobaltates

A study is reported of the formation of Fe(II), Co(II), Ni(II), Cu(II), Zn(II), Ag(I) and Cd(II) hexacyanocobaltates. The results show that the precipitates form by reaction of the metal ions with KCo(CN)(6)(2-) ion-pairs in 1:1 ratio, followed by solid phase transformations.     

New Complexes of Mn(II), Co(II), Ni(II), Cu(II), Zn(II) and Cd(II) with 3,3-dimethylglutaric Acid

Conditions for the preparation of Mn(II), Co(II), Ni(II), Cu(II), Zn(II) and Cd(II)3,3-dimethylglutarates were investigated and their quantitative composition, solubility in water at 293 K and magnetic moments were determined. IR spectra and powder diffraction patterns of the complexes prepared with general formula MC₇H₁₀O₄⋅nH₂O (n=0−2) were recorded and their thermal decomposition in air were studied. During heating the hydrated complexes of Mn(II),Co(II), Ni(II) and Cu(II) are dehydrated in one step and next all the anhydrous complexes decompose to oxides directly (Mn, Co, Zn) or with intermediate formation free metal (Ni,Cu) or oxocarbonates (Cd). The carboxylate groups in the complexes studied are bidentate. The magnetic moments for the paramagnetic complexes of Mn(II), Co(II), Ni(II) and Cu(II)attain values 5.62, 5.25, 2.91 and 1.41 M.B., respectively. This revised version was published online in August 2006 with corrections to the Cover Date.     

Complexes of Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) with 4-chloro-2-methoxybenzoic acid anion

The complexes of 4-chloro-2-methoxybenzoic acid anion with Mn²⁺, Co²⁺, Ni²⁺, Cu²⁺ and Zn²⁺ were obtained as polycrystalline solids with general formula M(C₈H₆ClO₃)₂·nH₂O and colours typical for M(II) ions (Mn – slightly pink, Co – pink, Ni – slightly green, Cu – turquoise and Zn – white). The results of elemental, thermal and spectral analyses suggest that compounds of Mn(II), Cu(II) and Zn(II) are tetrahydrates whereas those of Co(II) and Ni(II) are pentahydrates. The carboxylate groups in these complexes are monodentate. The hydrates of 4-chloro-2-methoxybenzoates of Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) heated in air to 1273 K are dehydrated in one step in the range of 323–411 K and form anhydrous salts which next in the range of 433–1212 K are decomposed to the following oxides: Mn₃O₄, CoO, NiO and ZnO. The final products of decomposition of Cu(II) complex are CuO and Cu. The solubility value in water at 293 K for all complexes is in the order of 10^–3 mol dm^–3. The plots of χ_M vs. temperature of 4-chloro-2-methoxybenzoates of Mn(II), Co(II), Ni(II) and Cu(II) follow the Curie–Weiss law. The magnetic moment values of Mn²⁺, Co²⁺, Ni²⁺ and Cu²⁺ ions in these complexes were determined in the range of 76−303 K and they change from: 5.88–6.04 μ_B for Mn(C₈H₆ClO₃)₂·4H₂O, 3.96–4.75 μ_B for Co(C₈H₆ClO₃)₂·5H₂O, 2.32–3.02 μ_B for Ni(C₈H₆ClO₃)₂·5H₂O and 1.77–1.94 μ_B for Cu(C₈H₆ClO₃)₂·4H₂O.     

New complexes of Mn(II), Co(II), Ni(II) AND Cu(II) with 2,2’- OR 2,4’-bipyridine and formates (Synthesis, thermal and other properties)

New mixed-ligand complexes with empirical formulae: Mn(2-bpy)_1.5L₂·2H₂O, M(2-bpy)₂L₂·3H₂O (M(II)=Co, Cu), Ni(2-bpy)₃L₂·4H₂O and M(2,4’-bpy)₂L₂·2H₂O (where 2-bpy=2,2’-bipyridine, 2,4’-bpy=2,4’-bipyridine; L=HCOO^– ) have been obtained in pure solid-state. The complexes were characterized by chemical and elemental analysis, IR and VIS spectroscopy, conductivity (in methanol and dimethylsulfoxide). The way of metal-ligand coordination discussed. The formate and 2,4’-bpy act as monodentate ligands and 2-bpy as chelate ligand. The new complexes with ligand isomerism were identified. During heating the complexes lose water molecules in one or two steps. Thermal decomposition after dehydration is multistage and yields corresponding metal oxides as final products. A coupled TG-MS system was used to analysis principal volatile thermal decomposition (or fragmentation) products of Ni(2,4’-bpy)₂(HCOO)₂·2H₂O under dynamic air or argon atmosphere.     

Thermal and Spectral Characterization of 5-Cholro-2-methoxybenzoates of Mn(II), Co(II), Ni(II), Cu(II) and Zn(II)

The thermal stabilities of 5-chloro-2-methoxybenzoates of Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) were studied in air and nitrogen atmospheres. The complexes were obtained as mono-, di-, tetra-and pentahydrates with a metal to ligand ratio of 1:2 and with colours typical for M²⁺ ions (Mn-slightly pink, Co-pink, Ni-green, Cu-blue and Zn-white) and as polycrystalline compounds. When heated they dehydrate to form anhydrous salts which nextare decomposed to the oxides of the respective metals in air while in nitrogen to the mixtures of metal oxides and oxychlorides and carbon. The most thermally stable in air, nitrogen and argon atmospheres is 5-chloro-2-methoxybenzoate of Cu(II) while the least thermally stable is that of Co(II). This revised version was published online in July 2006 with corrections to the Cover Date.     

N-vinylcarbazole polymerization by 13X molecular sieve exchanged with Mn(II), Co(II), Ni(II), Cu(II) and Zn(II)

The polymerization of N-vinylcarbazole by 13X molecular sieves modified by five different transition metal ions, viz. Mn(II), Co(II), Ni(II), Cu(II) and Zn(II), has been studied under various conditions. The order of reactivity follows the trend: Mn(II) ≈ Cu(II) > Co(II) > Zn(II) > Ni(II) at pH ∼ 3.55 and an exchange level of 30% of the metal ion. The polymerizations are believed to occur by a dual-ion-initiation mechanism in which both metal ions and proton centres participate. The overall energy of activation (E_a) for each system decreases with decreasing pH of the exchanging salt solution. Average activation energy on proton centre (E_H) and that on metal ion centre (E_a) have been evaluated for each system. E_a, E_H and E_c have been shown to correlate with one another. The molecular weights and their distributions are affected by the nature of the metal ion and also by the protonic centres. The possibility of a correlation of the catalytic activity of the modified 13X with ionic radius, electronegativity and normal co-ordination number has been examined.     

Synthesis, spectral characterization, and thermal behavior of mononuclear Cu(II), Co(II), Ni(II), Mn(II), and Zn(II) complexes with 5-bromosalycilaldehyde isonicotinoylhydrazone

A bidentate/tridentate 5-bromosalycilaldehyde isonicotinoylhydrazone Schiff base was synthesized by condensing 5-bromosalycilaldehyde with isonicotinoylhydrazine. Cu(II), Co(II), Ni(II), Mn(II) and Zn(II) complexes of this chelating ligand were synthesized using nitrates of these metals. The ligand and the complexes were characterized by elemental analysis, UV–Vis, IR and EPR spectroscopy, conductance and magnetic susceptibility measurements, fluorescence, cyclic voltammetry and thermogravimetric analysis. The ligand and Zn(II) complex exhibits solid-state photoluminescence at room temperature.     

Salisaldehyde-2-aminobenzimidazole schiff base complexes of Fe(III), Co(II), Ni(II), Cu(II), Zn(II) and Cd(II)

New metal complexes of Fe(III), Co(II), Ni(II), Cu(II), Zn(II) and Cd(II) with salicylidine-2-aminobenzimidazole (SABI) are synthesized and their physicochemical properties are investigated using elemental and thermal analyses, IR, conductometric, solid reflectance and magnetic susceptibility measurements. The base reacts with these metal ions to give 1:1 (Metal:SABI) complexes; in cases of Fe(III), Co(II), Cu(II), Zn(II) and Cd(II) ions; and 1:2 (Metal:SABI) complexes; in case of Ni(II) ion. The conductance data reveal that Fe(III) complex is 2:1 electrolyte, Co(II) is 1:2 electrolyte, Cu(II), Zn(II) and Cd(II) complexes are 1:1 electrolytes while Ni(II) is non-electrolyte. IR spectra showed that the ligand is coordinated to the metal ions in a terdentate mannar with O, N, N donor sites of the phenloic -OH, azomethine -N and benzimidazole -N3. Magnetic and solid reflectance spectra are used to infer the coordinating capacity of the ligand and the geometrical structure of these complexes. The thermal decomposition of the complexes is studied and indicates that not only the coordinated and/or crystallization water is lost but also that the decomposition of the ligand from the complexes is necessary to interpret the successive mass loss. Different thermodynamic activation parameters are also reported, using Coats-Redfern method. This revised version was published online in July 2006 with corrections to the Cover Date.