Divalent transition metal complexes of 3,5-pyrazoledicarboxylate

New divalent transition metal 3,5-pyrazoledicarboxylate hydrates of empirical formula Mpz(COO)₂(H₂O)₂, where M=Mn, Co, Ni, Cu, Zn and Cd (pz(COO)₂=3,5-pyrazoledicarboxylate), metal hydrazine complexes of the type Mpz(COO)₂N₂H₄ where M=Co, Zn or Cd and Mpz(COO)₂nN₂H₄·H₂O, where n=1 for M=Ni and n=0.5 for M=Cu have been prepared and characterized by physico-chemical methods. Electronic spectroscopic data suggest that Co and Ni complexes adopt an octahedral geometry. The IR spectra confirm the presence of unidentate carboxylate anion (Δν=ν_asy(COO^–)–ν_sym(COO^–)>215 cm^–1) in all the complexes and bidentate bridging hydrazine (ν_N–N=985–950 cm^–1) in the metal hydrazine complexes. Both metal carboxylate and metal hydrazine carboxylate complexes undergo endothermic dehydration and/or dehydrazination followed by exothermic decomposition of organic moiety to give the respective metal oxides as the end products except manganese pyrazoledicarboxylate hydrate, which leaves manganese carbonate. X-ray powder diffraction patterns reveal that the metal carboxylate hydrates are isomorphous as are those of metal hydrazine complexes of cobalt, zinc and cadmium.     

A comparative study on the thermal decomposition of some transition metal maleates and fumarates

Thermal decomposition of M(mal/fum)·xH₂O (M=Mn, Co, Ni) has been studied in static air atmosphere from ambient to 500°C employing TG-DTG-DTA, XRD and IR spectroscopic techniques. After dehydration the anhydrous maleate salts decompose to metal oxalate in the temperature range of 320–360°C, which at higher temperature undergo an abrupt oxidative pyrolysis to oxides. The anhydrous fumarate salts have been found to decompose directly to oxide phase. A comparison of thermal analysis reveals that fumarates are thermally more stable than maleates.     

Synthesis, thermal and other studies of 2,4'-bipyridine-dichloroacetato complexes of Mn(II), Co(II), Ni(II) and Cu(II)

Four new mixed ligand complexes were prepared by the reaction of title metal dichloroacetates and 2,4'-bipyridine. The general formulae of synthesized compounds are M(2,4'-bpy)₂(CCl₂HCOO)₂·nH₂O (where M(II)=Mn, Co, Ni, Cu; 2,4'-bpy=2,4'-bipyridine, n=2 or 4). The complexes have been isolated from aqueous media and characterized by chemical analysis, molar conductance (in MeOH, DMSO and DMF), magnetic, IR and VIS spectral studies. The nature of metal(II)-ligand coordination is discussed. The thermal behaviour of obtained complexes was studied by thermal analysis and TG-MS techniques in air. IR, X-ray powder diffraction and thermoanalytical data were used for the determination of solid intermediate products of the thermal decomposition. The principal volatile products of thermal decomposition of complexes were proved by mass spectroscopy: H₂O⁺, CO⁺ ₂, HCl⁺ ₂, Cl⁺ ₂, NO⁺ and other. This revised version was published online in July 2006 with corrections to the Cover Date.     

Thermal study of zinc(II) 4-chlorosalicylate complex compounds with bioactive ligands

Three new complex compounds of general formula Zn{4-ClC₆H₃-2-(OH)COO}₂⋅L₂⋅nH₂O (where L=thiourea (tu), nicotinamide (nam), caffeine (caf), n=2,3), were prepared and characterized by chemical analysis, IR spectroscopy and their thermal properties were studied by TG/DTG, DTA methods. It was found that the thermal decomposition of hydrated compounds starts with the release of water molecules. During the thermal decomposition of anhydrous compounds the release of organic ligands take place followed by the decomposition of salicylate anion. Zinc oxide was found as the final product of the thermal decomposition performed up to 650°C. RTG powder diffraction method, IR spectra and chemical analysis were used for the determination of products of the thermal decomposition.     

Thermal study of zinc(II) salicylate complex compounds with bioactive ligands

Five new complex compounds of general formula Zn(Hsal)_2·L₂·nH₂O (where Hsal=OHC₆H₄COO^-, L=thiourea (tu), nicotinamide (nam), caffeine (caf), theobromine (tbr), n=2-4), were prepared and characterized by chemical analysis, IR spectroscopy and studied by methods of thermal analysis (TG/DTG, DTA). It was found that the thermal decomposition of hydrated compounds starts with the release of water molecules. During the thermal decomposition of anhydrous compounds the release of organic ligands take place followed by the decomposition of salicylate anion. Zinc oxide was found as the final product of the thermal decomposition heated up to 800°C. RTG powder diffraction method, IR spectra and chemical analysis were used for the determination of products of the thermal decomposition. This revised version was published online in August 2006 with corrections to the Cover Date.     

Synthesis and Characterization of New Unsymmetrically Substituted Phthalocyanines

 Unsymmetric metallophthalocyanines (M=Zn, Co, Ni) carrying alkylthio and acetyloxyethylthio groups on peripheral positions were prepared from 4,5-bis-alkylthio-phthalonitrile, 4,5-bis-(acetyloxyethylthio)-phthalonitrile, and the corresponding anhydrous metal salts Zn(CH₃COO)₂, NiCl₂, and CoCl₂. The extremely soluble compounds were characterized by their IR, ¹H NMR, and UV/Vis spectra. Their long wavelength absorption band was found to be bathochromically shifted; their solubility is superior to that of symmetrical phthalocyanines.     

Thermal,spectral and magnetic behaviour of 4-chloro-2-methoxybenzoates of light lanthanides(III)

4-Chloro-2-methoxybenzoates of light lanthanides(III) were obtained as mono-, di-or trihydrates with metal to ligand ratio of 1:3 and general formula Ln(C₈H₆ClO₃)₃·nH₂O, where n=1 for Ln=Ce, Pr, n=2 for Ln=Nd, Sm, Eu, Gd and n=3 for Ln=La. The complexes were characterized by elemental analysis, IR spectra, thermogravimetric studies, X-ray diffraction and magnetic measurements. The carboxylate group appears to be a symmetrical bidentate, chelating ligand. All complexes seem polycrystalline compounds. Their thermal stabilities were determined in air. When heated they dehydrate to form anhydrous salts which next are decomposed to the oxides of the respective metals. The solubilities of light lanthanide(III) 4-chloro-2-methoxybenzoates in water at 293 K are of the order of 10⁻⁵ mol dm⁻³. The magnetic moments were determined over the range of 77–300 K. They obey the Curie-Weiss law. The values of μ_eff calculated for all compounds are close to those obtained for Ln³⁺ by Hund and Van Vleck. The results indicate that there is no influence of the ligand field of 4f electrons on lanthanide ions and the metal ligand bonding is mainly electrostatic in nature.     

Synthesis and Characterization of New Unsymmetrically Substituted Phthalocyanines

Summary.  Unsymmetric metallophthalocyanines (M=Zn, Co, Ni) carrying alkylthio and acetyloxyethylthio groups on peripheral positions were prepared from 4,5-bis-alkylthio-phthalonitrile, 4,5-bis-(acetyloxyethylthio)-phthalonitrile, and the corresponding anhydrous metal salts Zn(CH₃COO)₂, NiCl₂, and CoCl₂. The extremely soluble compounds were characterized by their IR, ¹H NMR, and UV/Vis spectra. Their long wavelength absorption band was found to be bathochromically shifted; their solubility is superior to that of symmetrical phthalocyanines. Received July 27, 1999. Accepted (revised) September 30, 1999     

Synthesis and Thermal Properties of 4,4'-bipyridine Adducts of Mn(II), Co(II), Ni(II) and Cu(II) Monochloroacetate

The complexes with the empirical formula M(4-bipy)(ClCH₂COO)₂ ×nH₂O (where: 4-bipy=4,4'-bipyridine, L=ClCH₂ COO^–, M (II)=Mn, Co, Ni, Cu) were prepared and characterized via the IR and electronic (VIS) spectra and conductivity measurements. Thermal decomposition of these compounds was studied. During heating in air dehydration processes occur. The anhydrous compounds decompose at high temperature to oxides. The principal volatile mass fragments correspond to: H₂O, CO₂, CH₃Cl, HCl, Cl₂ and other. This revised version was published online in August 2006 with corrections to the Cover Date.     

Synthesis and characterization of some metal(II) and sodium ions with cyclopentane-1,2,3,4-tetracarboxylate anion

New divalent metal cyclopentane-1,2,3,4-tetracarboxylate (CPTC) hydrates of empirical formula M₂C₅H₆(COO)₄ · nH₂O, where M = Ni, Co, Cu, or Zn and n = 3?6, and sodium CPTC Na₃C₅H₆COOH(COO)₃ · 7H₂O have been prepared and characterized by elemental analysis, magnetic measurements, thermal, and infrared spectral studies. For the sodium salt, a single crystal (Na₃C₅H₆COOH(COO)₃ · 8H₂O) was also obtained. IR spectra of the metal(II) complexes indicate the coordination of metal ions through all carboxylates. For the sodium compound, a band at 1681 cm^?1 indicates that some carboxylic groups have not been deprotonated. The presence of protonated carboxylic group was also confirmed by an X-ray single crystal analysis. On heating in air atmosphere, all complexes lose water molecules and next anhydrous compounds decompose to corresponding metal oxides and sodium carbonate.     

Synthesis and characterization thesulphides type ZnS(1-x)MSx

ZnS_(1-x)MS_x(x=0.01 and M=Mn²⁺, Cu²⁺ and Eu²⁺) compounds have been obtained by precipitation from homogeneous solutions of zinc, copper, manganese and europium salts, with S^2- as the precipitating anion, formed by the decomposition of thioacetamide. The thermal study of the milled zinc acetate, thioacetamide, copper acetate, manganese acetate and europium nitrate, respectively, was studied for thermal analyis TG/DSC. XRD respect exhibits a zinc blend crystal structure. This revised version was published online in August 2006 with corrections to the Cover Date.     

Thermal expansion in 3d-metal Prussian Blue Analogs—A survey study

We present a comprehensive study of the structural properties and the thermal expansion behavior of 17 different Prussian Blue Analogs (PBAs) with compositions M^II₃[(M′)^III(CN)₆]₂·nH₂O and M^II₂[Fe^II(CN)₆]·nH₂O, where M^II=Mn, Fe, Co, Ni, Cu and Zn, (M′)^III=Co, Fe and n is the number of water molecules, which range from 5 to 18 for these compounds. The PBAs were synthesized via standard chemical precipitation methods, and temperature-dependent X-ray diffraction studies were performed in the temperature range between −150 °C (123 K) and room-temperature. The vast majority of the studied PBAs were found to crystallize in cubic structures of space groups Fm3?m, F4?3m and Pm3?m. The temperature dependence of the lattice parameters was taken to compute an average coefficient of linear thermal expansion in the studied temperature range. Of the 17 compounds, 9 display negative values for the average coefficient of linear thermal expansion, which can be as large as 39.7×¹0⁻⁶ K⁻¹ for Co₃[Co(CN)₆]₂·12H₂O. All of the M^II₃[Co^III(CN)₆]₂·nH₂O compounds show negative thermal expansion behavior, which correlates with the Irving–Williams series for metal complex stability. The thermal expansion behavior for the PBAs of the M^II₃[Fe^III(CN)₆]₂·nH₂O family are found to switch between positive (for M=Mn, Co, Ni) and negative (M=Cu, Zn) behavior, depending on the choice of the metal cation (M). On the other hand, all of the M^II₂[Fe^II(CN)₆]·nH₂O compounds show positive thermal expansion behavior.     

Synthesis and Electrochemistry of Soluble Phthalocyanine Complexes Containing Four Peripheral Dihexyl and Dihexylhexylmalonate Residues

Summary.  Tetrasubstituted phthalocyanines bearing four dihexylmalonate or dihexylhexylmalonate residues on the periphery (M[Pc(CH(COOC₆H₁₃)₂)₄] or M[Pc(C(COOC₆H₁₃)₂ C₆H₁₃)₄]; M = Pd(II), Cu(II), Co(II)) were synthesized from the anhydrous metal salts and the corresponding phthalonitriles. The complexes were only slightly soluble in polar solvents such as methanol and ethanol, but more soluble in less polar solvents such as benzene, toluene, and even hexane. The spectroscopic properties of the complexes were affected strongly by the electron withdrawing malonate units. Cyclic voltammetry on a platinum electrode in dichloromethane showed ligand-based one-electron transfers for Cu and Pd compounds, whereas the Co complex displayed metal-based or/and ligand-based one-electron transfers depending on the supporting electrolyte anion. The structures were confirmed by elemental analysis, ¹H NMR, ¹³C NMR, IR, mass (EI and FAB), and UV/Vis spectroscopy. Received November 24, 2000. Accepted (revised) January 2, 2001     

Transition metal complexes of heterocyclic Schiff base

Metal complexes of Schiff base derived from 2-furancarboxaldehyde and 2-aminobenzoic acid (HL) are reported and characterized based on elemental analyses, IR, ¹H NMR, UV-Vis, solid reflectance, magnetic moment, molar conductance and thermal analysis. The ligand dissociation as well as the metal-ligand stability constants have been calculated pH-metrically at 25°C and ionic strength μ=0.1 (1 M NaCl). The complexes are found to have the formulae [M(HL)₂](X)_n·yH₂O (where M=Fe(III) (X=Cl, n=3, y=4), Co(II) (X=Cl, n=y=2), Ni(II) (X=Cl, n=y=2), Cu(II) (X=Cl, n=y=2) and Zn(II) (X=AcO, n=y=2)) and [UO₂(L)₂]·2H₂O. The thermal behaviour of these chelates is studied and the activation thermodynamic parameters are calculated using Coats-Redfern method. The ligand and its metal complexes show a biological activity against some bacterial species.     

Syntheses and spectrothermal studies of triethanolamine complexes of Co(II), Ni(II), Cu(II) and Cd(II) squarates

The triethanolamine complexes, [M(tea)₂]sq·nH₂O, (n=2 for Co(II), n=0 for Ni(II), Cu(II) and n=1 for Cd(II), tea=triethanolamine, sq²⁻=squarate), have been synthesized and characterized by elemental analyses, magnetic susceptibility and conductivity measurements, UV-Vis and IR spectra, and thermal analyses techniques (TG, DTG and DTA). The Co(II), Ni(II) and Cu(II) complexes possess octahedral geometry, while the Cd(II) complex is monocapped trigonal prismatic geometry. Dianionic squarate behaves as a counter ion in the complexes. The thermal decomposition of these complexes takes place in three stages: (i) dehydration, (ii) release of the tea ligands and (iii) burning of organic residue. On the basis of the first DTG_max of the decomposition, the thermal stability of the anhydrous complexes follows the order: Ni(II), 289°C>Co(II), 230°C>Cu(II), 226°C>Cu(II), 170°C in static air atmosphere. The final decomposition products — the respective metal oxides — were identified by FTIR spectroscopy.     

Thermal behavior of some new triazole derivative complexes

A series of new complexes with mixed ligands of the type [ML(C₃H₃O₂)₂]·nH₂O (((1) M=Mn, n=1; (2) M=Co(II), n=2; (3) M=Ni(II), n=4; (4) M=Cu(II), n=1.5; (5) M=Zn(II), n=0; L=3-amino-1,2,4-triazole and (C₃H₃O₂)=acrylate anion) were synthesized and characterised by chemical analysis and IR data. In all complexes the 3-amino-1,2,4-triazole acts as bridge while the acrylate acts as bidentate ligand except for complex (5) where it is found as unidentate. The thermal behaviour steps were investigated in nitrogen flow. The thermal transformations are complex processes according to TG and DTG curves including dehydration, acrylate ion and 3-amino-1,2,4-triazole degradation respectively. The final products of decomposition are the most stable metal oxides, except for complex (4) that leads to metallic copper.     

Studies on the synthesis and thermal decomposition mechanisms of rare-earth metal (Pr,Nd, Sm) salt hydrates of 3-nitro-1,2,4-triazol-5-one

Three new rare-earth metal (Pr, Nd and Sm) salt hydrates of 3-nitro-1,2,4-triazol-5-one (NTO) were prepared and characterized. The thermal behaviour of the three salt hydrates, M(NTO)₃·nH₂O (M=Pr and Nd,n=9;M=Sm,n=8) were studied by means of TG and DSC under conditions of linear temperature increase. The thermal decomposition intermediates were determined by means of IR, MS and X-ray diffraction spectrometry. The thermal decomposition mechanisms of these hydrates were proposed as follows: We express our thanks to Professor Zhu Chunhua, Associate Professor Fu Xiayun, and Lecturers Fan Tao and Liang Yanjun for their help in this work.     

Thermal behaviour of some new complexes with bismacrocyclic ligands as potential biological active species

Novel complexes of type [M₂LCl₄]·nH₂O ((1) M:Ni, n = 5; (2) M:Cu, n = 0 and (3) M:Zn, n = 2; L: ligand resulted from 1,2-phenylenediamine, 3,6-diazaoctane-1,8-diamine and formaldehyde template condensation) were synthesised and characterised. The features of complexes have been assigned from microanalytical, IR and UV–Vis data. The thermal analyses have evidenced the thermal intervals of stability and also the thermodynamic effects that accompany them. Processes as water or hydrochloric acid elimination as well as oxidative degradation of the organic ligand were observed. Complexes display a different thermal behaviour as result of dissimilar chemical interaction of metal ions with chloride anions. The final product of decomposition was metal(II) oxide as powder X-ray diffraction indicated.     

Synthesis, characterization and thermal studies on solid compounds of 2-chlorobenzylidenepyruvate of heavier trivalent lanthanides and yttrium(III)

Solid-state compounds of general formula LnL_3⋅nH₂O, where Ln represents heavier lanthanides and yttrium and L is 2-chlorobenzylidenepyruvate, have been synthesized. Chemical analysis, simultaneous thermogravimetry-differential analysis (TG-DTA), differential scanning calorimetry (DSC), X-ray powder diffractometry, elemental analysis and infrared spectroscopy have been employed to characterize and to study the thermal behaviour of these compounds in dynamic air atmosphere. On heating these compounds decompose in four (Gd, Tb, Ho to Lu, Y) or five (Eu, Dy) steps. They lose the hydration water in the first step and the thermal decomposition of the anhydrous compounds up to 1200°C occurs with the formation of the respective oxide, Tb₄O₇ and Ln₂O₃ (Ln=Eu, Gd, Dy to Lu and Y) as final residue. The dehydration enthalpies found for these compounds (Eu, to Lu and Y) were: 65.77, 55.63, 86.89, 121.65, 99.80, 109.59, 131.02, 119.78, 205.46 and 83.11 kJ mol^-1, respectively.     

Potentiometric and Thermogravimetric Studies on Some Metal–Oxine–Sulphadrugs ternary Complexes

Formation constants (logK _MAL ^MA) of the mixed complexes of the type M–A–L (where M=Mn(II), Co(II), Ni(II), Cu(II), Ce(III), Th(IV), and UO₂(II); A=oxine and L=sulphamerazine or sulphadiazine) have been determined pH-metrically in 60% (v/v) ethanol–water mixture at 25°C and constant ionic strength (μ=0.1 M NaCl). The mode of chelation was ascertained by conductivity measurements. The stability sequence with respect to metal ions have been found to be Cu(II)>Ni(II)>Co(II)>Mn(II) and Th(IV)>UO₂(II)>Ce(III). CuAL ternary solid complexes have been prepared and characterized on the basis of elemental analysis and IR-spectroscopy. The thermal degradations of the prepared complexes are discussed in an attempt to assign the intermediate compounds formed. This revised version was published online in August 2006 with corrections to the Cover Date.