Thermoanalytical study of imidazole-substituted coordination compounds: Cu (II)-and Zn (II)-complexes of bis (1-methylimidazol-2-yl) ketone (original) (raw)
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Natural Science, 2010
A series of new mixed ligand complexes of cobalt(II), nickel(II), copper(II) and cadmium(II) have been synthesized with 3-benzyl-1H-4-[(2methoxybenzylidine) amino]-1, 2, 4-triazole-5thione (MBT), 3-bezyl-1H-4-[(4-chlorobenzylidine) amino]-1, 2, 4-triazole-5-thione (CBT), 3-benzyl-1H-4-[(4-nitrobenzylidine)amino]-1, 2, 4-triazole-5-thione (NBT) and dehydroacetic acid sodium salt (Nadha). The mixed ligand complexes have been characterized by elemental analysis, spectroscopic spectral measurements (IR, UV-Vis.), molar conductance, magnetic measurements and thermal studies. The stoichiometry of these complexes is M:L 1 :L 2 = 1:1:1, 1:2:1 or 1:1:2 where L 1 = NBT, CBT and MBT and L 2 = Nadha. Tetrahedral structure was proposed for all Cd(II) mixed ligand complexes while the square planar geometry was proposed for Cu(II) mixed ligand complex with NBT. Octahedral structure was proposed for Ni(II), Co(II) mixed ligand complexes and Cu(II) mixed ligand complexes with CBT and MBT ligands. The thermal decomposition study of the prepared complexes was monitored by TG, DTG and DTA analysis in dynamic nitrogen atmosphere. TG, DTG and DTA studies confirmed the chemical formulations of theses complexes. The kinetic parameters were determined from the the thermal decomposition data using the graphical methods of Coats-Redfern and Horwitz-Metzger. Thermodynamic parameters were calculated using standard relations.
Thermal decomposition of copper-azole complexes
Journal of Thermal Analysis, 1989
The thermal decomposition of complexes of the formulae: Cu(IMDAH)xCI 2, Cu(BIMDAH)~C12 (x = 2 or 4), Cu(BTAH)2CI2, Cu(5MBTAH)2C12, Cu(BIMDA)2, Cu(PDZ)C12, and Cu(PYM)CI2 (IMDAH = imidazole, BIMDAH = benzimidazole; BTAH = benzotriazole; 5MBTAH = 5-methyl-benzotriazole; PDZ = pyridazine; PYM = pyrimidine) has been studied in an oxidizing environment using thermogravim~tric (TG) analysis. The TG profiles of all the complexes indicate degradation of the azole ligands and conversion to copper oxides. The Cu-azole complexes retain much higher fractions of the Cu in the degradation residue than the Cu(PDZ)C12 and Cu(PYM)CI 2 complexes which volatilize most of the Cu on thermal decomposition. These differences are interpreted on the basis ofmetalligand bonding and the participation of redox reactions in the thermal decomposition mechanism. Azole ligands are used extensively as corrosion inhibitors in the antique [1] and printed circuit board industries [2]. The coordination nature of the metal-azole bonding as well as the molecular bond strength are important factors in determining the effectiveness of the corrosion inhibition process [3, 4]. To investigate the metal-azole chemistry and their thermal properties, several model complexes have been prepared by directly reacting the free ligand with a metal compound. Previously, we and others have used X-ray photoelectron spectroscopy (XPS) [3, 5], Fourier transform infrared spectroscopy (FTIR) [5], and X-ray diffraction [6] to study the coordination chemistry of these materials. In the current work we employ thermogravimetric (TG) analysis to investigate their thermal decomposition mechanisms [4]. Several authors have studied the effect of coordination chemistry and lattice distortion on the thermal stability of metal complexes [7-9]. The interpretation of the thermal degradation profile is complicated especially for copper complexes. This paper reports on the synthesis of several copper-azole complexes involving CuCI z and imidazole (IMDAH), benzimidazole (BIMDAH), benzotriazole
Journal of Analytical and Applied Pyrolysis, 1986
The thermal behaviour of 6-amino-1,3-dimethyl&phenylazouracil complexes of Co(II), Ni(II), Cu(I1) and Ag(1) ions was studied by IR, thermogravimetric and differential scanning calorimetric techniques. IR spectroscopy applied to these complexes heated in air allowed the elucidation of the decomposition steps and the nature of the intermediate products. The Cu(I1) complexes led to the same products on heating at 225'C [bis(l,3-dimethyl-2,4-dioxo-5-phenyfazo-l,2,3,4-tetrahydropyrimidine-6-oxido)copper(II)]. fi N=N-Ph DZH NH, Scheme 1. 0165-2370/86/$03.50 0 1986 Elsevier Science Publishers B.V.
Natural Science, 2011
Anodic oxidation of Co, Cu, Zn, and Sn metals in an acetone solution of 1,1-malonayl-bis(4-p-Chloro-phenylthiosemicarbazide) yields complexes of composition with general formula [Co 2 (pClMaTS)(H 2 O) 6 ]•2H 2 O, [Cu 2 (pClMaTS)(H 2 O) 6 ], [Zn 2 (pClMaTS)(H 2 O) 6 ] and [Sn 2 (pClMaTS)(H 2 O) 6 ]•2H 2 O. Chelation was investigated based on elemental analysis, conductivity, magnetic moment, spectral (UV-Vis, IR, Raman, 1 HNMR, mass), thermal, and ESR studies. The Raman and infrared spectral studies suggests the tridentate behavior of the ligand from each tail. Since the ligand has two thiosemicarbazide groups, it may acts in an SNO tridentate fashion from each side with one of the two metal ions forming a polynuclear complex coordinating through both of the lone pair of electrons the enolic oxygen of the carbonyl group (C=O), the azomethine nitrogen (C=N) and the thioenol form of the thiocarbonyl group (C=S). The differential thermogravimetric analysis (DTG) curves were used to study the decomposition steps of the isolated complexes using Horowitz-Metzger (HM) and Coats-Redfern (CR) methods. The kinetic thermodynamic parameters such as: E*, ∆H*, ∆S*and ∆G* are calculated from the DTG curves.
Chinese Journal of Chemistry, 2010
The Ni(II), Cu(II) Co(II) and Zn(II) complexes of 2,3-hydroxyimino-4-phenyl-6-phenyazo-1-thia-4,5-diaza- cyclohexa-5-diene (H2L) were synthesized. Thermal behavior of these complexes was studied in dynamic nitrogen atmosphere by TA (thermogravimetric analysis), DTA (differential thermal analysis) and DTG (differential thermal gravimetry) techniques. The reaction order, the activation energies, the entropies, the enthalpies, the free energies, and the pre-exponential factors of the thermal decomposition reactions were calculated from the thermogravimetric curves. The kinetic analysis of the thermogravimetric data was performed by using several methods such as MacCallum-Tanner (MT), van Krevelen (vK), Madhusudanan-Krishnan-Ninan (MKN), Wanjun-Yuwen-Hen-Cunxin (WYHC), Horowitz-Metzger (HM) and Coats-Redfern method (CR) based on the single heating rate. Most appropriate methods were determined for each decomposition step according to the least-square linear regression. The Ni(II), Cu(II) Co(II) and Zn(II) complexes displayed one- or two-stage decomposition pattern when heating in a dynamic nitrogen atmosphere and metal oxides remained as end products of the complexes. The characterization of the end products of the decomposition was performed by X-ray diffraction.
The Journal of Chemical Thermodynamics, 2008
Two substituted N-acylthioureas and the respective Ni(II) and Cu(II) complexes were synthesized, namely: N,N-din -butyl-N 0-thenoylthiourea (Hnbtu); N,N-di-iso-butyl-N 0-thenoylthiourea (Hibtu); bis[N,N-din -butyl-N 0-thenoylthioureato]nickel(II), [Ni(nbtu) 2 ]; bis[N,N-din -butyl-N 0-thenoylthioureato]copper(II), [Cu(nbtu) 2 ]; bis[N,N-di-iso-butyl-N 0-thenoylthioureato]nickel(II), [Ni(ibtu) 2 ]; bis[N,N-di-iso-butyl-N 0-thenoylthioureato]copper(II), [Cu(ibtu) 2 ]. The standard (p = 0.1 MPa) molar enthalpies of formation and sublimation of the two N-acylthioureas were measured, at T = 298.15 K, by rotating-bomb combustion calorimetry and Calvet microcalorimetry, respectively. The standard (p = 0.1 MPa) molar enthalpies of formation of the Ni(II) and Cu(II) complexes were determined, at T = 298.15 K, by high precision solution-reaction calorimetry. From the results obtained, the enthalpies of hypothetical metal-ligand and metal-metal exchange reactions, in the gaseous phase, were derived, thus allowing a discussion of the gaseous phase energetic difference between the complexation of Ni(II) and Cu(II) to 1,3-ligand systems with (S,O) ligator atoms.
Dyes and Pigments, 2001
The metal–ligand mole ratios and the stability constants of the Cu(II), Co(II), Ni(II) and Zn(II) complexes at 2-(5-bromo-2-pyridylazo)-5-diethylamino)phenol were determined using a spectrophotometric method at different temperatures (20, 30, 40 and 50±0.1 °C) and ionic strengths (0.05, 0.1 and 0.2) in 30% (v/v) aqueous ethanol. Plots of thermodynamic stability constants at zero ionic strength (ln K°) versus T−1 gave linear curves; the ensuing complex formation (ΔH° and ΔS°) values calculated from these plots. The changes in free energy for each metal–ligand system were evaluated.
Journal of Thermal Analysis and Calorimetry, 1999
The thermal decompositions of the complexes of N,N-dialkyl-N'-benzoylthioureas with Cu(II), Ni(II), Pd(II), Pt(II), Cd(II), Ru(III) and Fe(III) were studied by TG and DTA techniques. These metal complexes decompose in two stages: elimination of dialkylbenzamide, and total decomposition to metal sulphides or metals. The influence of the alkyl substituents in these benzoylthiourea chelates on the thermal behaviour of the metal complexes