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1.
Thermal behavior of various synthesized transition metal surfactant complexes of the type [M(CH3COO)4]2−[C12H25NH3
+]2 where M: Cu(II), Ni(II), Co(II) has been investigated using Thermogravimetric Analysis (TGA). It was found that pyrolytic
decomposition occurs with melting in metal complexes, and that metal oxides remain as final products. The activation energy
order obtained, E
Cu > E
Ni > E
Co, could be explained on the basis of size of transition metal ion and metal ligand bond strength. In the course of our investigation
on the decomposition of complexes, we carried out a comparative study of different measurement and calculation procedures
for the thermal decomposition. A critical examination was made of the kinetic parameters of non-isothermal thermoanalytic
rate measurement by means of several methods such as Coats–Redfern (CR), Horowitz–Metzger (HM), van Krevelen (vK), Madhusudanan–Krishnan–Ninan
(MKN), and Wanjun–Yuwen–Hen–Cunxin (WYHC). The most appropriate method among these was determined for each decomposition step
according to the least-squares linear regression. It was found that the results obtained using CR method differ considerably
from HM method, as the former method involves a lot of approximations and is not much reliable. The application of thermoanalytic
techniques to the investigation of rate processes has also been discussed. 相似文献
2.
Zhang J Brodbelt JS Wang J 《Journal of the American Society for Mass Spectrometry》2005,16(2):139-151
The relative threshold dissociation energies of a series of flavonoid/transition metal/auxiliary ligand complexes of the type [MII (flavonoid - H) auxiliary ligand]+ formed by electrospray ionization (ESI) were measured by energy-variable collisionally activated dissociation (CAD) in a quadrupole ion trap (QIT). For each of the isomeric flavonoid diglycoside pairs, the rutinoside (with a 1-6 inter-saccharide linkage) requires a greater CAD energy and thus has a higher dissociation threshold than its neohesperidoside (with a 1-2 inter-saccharide linkage) isomer. Likewise, the threshold energies of complexes containing flavones are higher than those containing flavanones. The monoglycoside isomers also have characteristic threshold energies. The flavonoids that are glycosylated at the 3-O- position tend to have lower threshold energies than those glycosylated at the 7-O- or 4'-O- position, and those that are C- bonded have lower threshold energies than the O- bonded isomers. The structural features that substantially influence the threshold energies include the aglycon type (flavanone versus flavone), the type of disaccharide (rutinose versus neohesperidose), and the linkage type (O- bonded versus C- bonded). Various computational means were applied to probe the structures and conformations of the complexes and to rationalize the differences in threshold energies of isomeric flavonoids. The most favorable coordination geometry of the complexes has a plane-angle of about 62 degrees , which means that the deprotonated flavonoid and 2,2'-bipyridine within a complex do not reside on the same plane. Stable conformations of five cobalt complexes and five deprotonated flavonoids were identified. The conformations were combined with the point charges and helium accessible surface areas to explain qualitatively the differences in threshold energies for isomeric flavonoids. 相似文献
3.
Transition metal dithiocarbamate complexes, [M(S2CN(C2H5)(CH2CH2OH)] (M=Co, Ni, Cu, Zn and Cd) have been prepared and characterized by elemental analysis and infrared spectra. Thermal decomposition
of all the complexes occurs in two or three stages. The first stage in all the complexes is always fast with 65-70% mass loss.
In all cases the end product is metal oxide except in the case of cobalt complex which gives Co metal as an end product. During
decomposition of copper complex, first CuS is formed at ~300°C which is converted into CuSO4 and finally CuO is formed. However, decomposition in helium atmosphere yields CuS. SEM studies of transition metal dithiocarbamates
reveal needle shape crystalline phase at room temperature and formation of metal sulphide/oxide at higher temperatures. The
activation energy varies in a large range of 33.8-188.3 kJ mol-1, being minimum for the Cu complex and maximum for the Zn complex possibly due to d
10 configuration. In the case of Ni, Zn and Cd complexes the order of reaction is two suggesting bimolecular process involving
intermolecular rearrangement. However, in other cases it is a unimolecular process. Large negative values of ΔS
# for all the complexes suggest that the decomposition process involves rearrangement.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
4.
Thermal decomposition of anhydrous Cu(HCOO)2 (1) affords H2, CO, CO2, H2O, HCuOOH, CuHCOO, Cu, and the polymeric product, which contains -CH2O,-C(O)OH-, and -RCH-0- groups. Dccomposition of1 proceeds in stages with formation of copper(I) formate as an intermediate. Possible pathways of decomposition ofI, including isomeric forms of the HCO2 radical as intermediates, were analyzed.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1406–1412, June, 1996. 相似文献
5.
Thermal solid-phase decomposition of anhydrous copper(ii) formate has been studied at 120–180 ° The rate of gas evolution during the decomposition depends on the depth of conversion and can be presented as the sum of first-order reaction rates and the rate of the autocatalytic process (a second-order reaction). The evolution of the solid phase during thermolysis has been observed by optical microscopy. The decomposition of copper formate is a complex topochemical process, a combination of homogeneous and heterogeneous transformations and dispersion of large crystals.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. l, pp. 72–76, January, 1996. 相似文献
6.
Dynamics of changes in microstresses during thermal decomposition of Cu(HCOO)2 crystals and their effect on the thermal decomposition kinetics were studied by IR spectroscopy at 105 to 120 °C. The formation of solid intermediate HCOOCu was observed, and the dynamics of its accumulation was followed. Kinetic regularities of transformation of HCOO groups were compared with those for gas evolution.For Communication 1, see Ref. 1.Translated from Izvestiya va Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 350–354, February, 1996. 相似文献
7.
Chen Donghua Yuan Yuhong Peng Zhenghe Jian Lihua Pan Qingcai Qin Zibin 《Thermochimica Acta》1998,320(1-2):291-295
Studies of the non-isothermal decomposition of M (mnt) (5-NO2-phen) (M=CoII, CuII, ZnII) were carried out by thermogravimetry. The thermal decomposition mechanisms and associated kinetics have been investigated. The kinetic parameters were obtained from an analysis of the TG–DTG curves by integral and differential methods. The most probable kinetic model functions were suggested by comparison of the kinetic parameters. Mathematical expressions for the kinetic compensation effect were derived. 相似文献
8.
9.
《Thermochimica Acta》1986,100(1):119-148
Organic solutions from the extractions of divalent manganese, cobalt, copper and zinc, trivalent gallium, indium and thallium, tetravalent vanadium and zirconium, and hexavalent uranium and molybdenum with trioctylamine (TOA, R3N) and trioctylmethylammonium chloride (TOMAC, R3R′NCl) in benzene were heated in vacua to prepare benzene-free complexes. The resulting complexes were examined by thermogravimetry and differential thermal analysis under an atmosphere of nitrogen, and their thermally decomposed products, such as volatile matters and residues, by gas chromatography, X-ray diffraction and infrared spectroscopy. Consequently, the thermal decomposition process of these complexes is discussed and the structure of the complexes is proposed on the basis of the results obtained. 相似文献
10.
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. 相似文献
11.
Ivakhnenko EP Starikov AG Minkin VI Lyssenko KA Antipin MY Simakov VI Korobov MS Borodkin GS Knyazev PA 《Inorganic chemistry》2011,50(15):7022-7032
A series of pseudo-octahedral metal (M = Mn, Fe, Co, Ni, Cu, Zn) complexes 4 of a new redox-active ligand, 2,4,6,8-tetra(tert-butyl)-9-hydroxyphenoxazin-1-one 3, have been synthesized, and their molecular structures determined with help of X-ray crystallography. The effective magnetic moments of complexes 4 (M = Mn, Fe, Co, and Ni) measured in the solid state and toluene solution point to the stabilization of their high-spin electronic ground states. Detailed information on the electronic structure of the complexes and their redox-isomeric forms has been obtained using density functional theory (DFT) B3LYP*/6-311++G(d,p) calculations. The energy disfavored low-spin structures of manganese, iron, and cobalt complexes have been located, and based on the computed geometries and distribution of spin densities identified as Mn(IV)[(Cat-N-SQ)](2), Fe(II)[Cat-N-BQ)](2), and Co(II)[Cat-N-BQ)](2) compounds, respectively. It has been shown that stabilization of the high-spin structures of complexes 4 (M = Mn, Fe, Co) is caused by the rigidity of the molecular framework of ligands 3 that sterically inhibits interconversions between the redox-isomeric forms of the complexes. The calculations performed on complex 4 (M = Co) predict that a suitable structural modification that might provide for stabilization of the low-spin electromeric forms and create conditions for the valence tautomeric rearrangement via stabilization of the low-spin electromer and narrowing energy gap between the low-spin ground state tautomer and the minimal energy crossing point on the intersection of the potential energy surfaces of the interconverting structures consists in the replacement of an oxygen in the oxazine ring by a bulkier sulfur atom. 相似文献
12.
《Journal of Inorganic and Nuclear Chemistry》1976,28(12):2221-2225
Thermal decomposition of methyl and dimethylthiourea complexes of several transition metals and of cadmium complexes with several thioureas and ureas were studied by thermogravimetric analysis in air and vacuum and stability relations established. In vacuum, dimethylthiourea complexes decompose to a mixture of metal chloride and sulfide; the organic products include dimethylthiourea, methylisothiocyanate, HCl and polymerized material. In air, intermediates are formed in which part of the organic ligand is retained followed by complete decomposition to inorganic salts at higher temperatures. The intermediate contains little sulfur and appears to be a substituted urea compound. 相似文献
13.
Madhusudanan P. M. Yusuff K. K. Mohammed Nair C. G. Ramachandran 《Journal of Thermal Analysis and Calorimetry》1975,8(1):31-43
Thermogravimetric (TG), derivative thermogravimetric (DTG) and differential thermal analysis (DTA) curves of CuL2 and NiL2 (L?=diethyl dithiocarbamate anion) in air are studied. The main decomposition temperature ranges are: For CuL2, DTG 250–350°, DTA 300–320° and for NiL2, DTG 290–390°, DTA 360–400°. Mass loss considerations at the main decomposition stages indicate conversion of the complex to sulphides. Mathematical analysis of TG data shows that first order kinetics are applicable in both cases. Kinetic parameters (energy and entropy of activation and preexponential factor) are reported.
相似文献14.
Thermogravimetric (TG), derivative thermogravimetric (DTG) and differential thermal analysis (DTA) curves of CuL2 and Pd(LH)2Cl2 (LH=salicylidene-2-aminofluorene and 2-hydroxy-1-naphthalidene-2-aminofluorene) in air are studied. Mass loss considerations at the main decomposition stages indicate conversion of the complex to oxides. Mathematical analysis of TG data shows that first order kinetics are applicable in all cases. Kinetic parameters (energy and entropy of activation and preexponential factor) are reported. 相似文献
15.
《Arabian Journal of Chemistry》2019,12(7):1070-1082
In the present work, thermal degradation behaviors of the Zn (II), Cd(II), and Hg(II) coordination polymers of fumaroyl bis (paramethoxyphenylcarbamide) (fbpmpc) have been investigated by using thermogravimetric (TG) analysis, differential thermal analysis (DTA) and derivative thermogravimetry (DTG) analysis under non-isothermal conditions in nitrogen atmosphere at multiple heating rates. TG–DTA study noteworthy inferred the presence of lattice water in outer sphere of all the polymers. The decomposition was carried out in three-four well-separated stages where involved the loss of water molecules in the first step followed by organic ligand. Furthermore, the kinetics and thermodynamic stabilities of multi-steps thermal degradation were evaluated. The activation energy (Ea), order of reaction (n), Arrhenius factor (A), enthalpy change (ΔH), entropy change (ΔS) and free energy change (ΔG) of coordination polymers were obtained by using the Coats–Redfern (CR) method. Ultimately, based on initial, half and final decomposition temperature, and kinetics parameters values the orders of thermal stability were estimated. 相似文献
16.
Hydrofluorothermal methods are shown to offer a facile route to a very large family of mid-late first row, transition metal fluorophosphates with 50 new compounds identified to date for manganese(III), iron(III), cobalt(II), and copper(II). Reactions of a transition metal fluoride with a phosphate source in a very low-water, high-fluoride content system and in the presence of framework charge balancing metal cations or template molecular cations, lead to materials with structures formed from linked M(O,F)(n) and P(O,F)(n) polyhedra. The structures of these materials, which contain a variety of 1, 2, and 3-dimensional motifs with a level of framework termination dependent upon their fluoride content, show numerous useful characteristics for functionality and applications. The new and unusual features of these fluorophosphate materials include interlayer spaces or channels lined with fluoride ions, metal polyhedra, M(O,F)(n), linked through vertex, edge, or face-sharing, and μ(2), μ(3), and μ(4) bridging fluoride ions. Preliminary characterization of the properties of some of these metal fluorophosphates is reported, including reductive lithium ion insertion, of interest for Li-ion battery positive electrodes, ion exchange reactions, the formation of nanoporous material derivatives through template destruction, and magnetic susceptibility behaviors. 相似文献
17.
18.
Thermal dehydration and decomposition processes of a Pd(II) coordination compound, [PdL4]Cl2·3H2O ( 1 ), (where L is 1‐allylimidazole) were studied by simultaneous TG/DSC techniques under constant heating rates condition. The released gas products were analyzed by online coupling a FTIR spectrometer to the TG equipment. The so obtained evolved gas analysis confirmed that only two ligand molecules were released and that a new 1‐allylimidazole Pd(II) complex, trans‐[PdL2Cl2] ( 2a ), was obtained. The same coordination compound was also prepared by heating 1 at 413.15 K in air atmosphere until a constant weight was reached 2b . Thermal decomposition mechanisms for the 2a and 2b complexes examined were proposed according to the three mass loss steps derived by TG data. Based on the model‐free isoconversional method described by Flynn–Wall–Ozawa (FWO), the dependencies of activation energy on the degree of conversion were determined. A model‐free “single point” method was also applied using the Kissinger equation, and derived results were compared to those of the former method. © 2005 Wiley Periodicals, Inc. Int J Chem Kinet 37: 667–674, 2005 相似文献
19.
Current micro review focuses on Earth-abundant molecular transition metal photosensitizers and catalysts for dye sensitized photoelectrochemical cells for direct solar energy storage. The possibility of direct conversion of solar energy into fluids (ethanol or methanol) or gases (hydrogen or methane) in a cost efficient way is considered a disruptive and innovative breakthrough for large-scale implementation of solar fuel technologies. At present, it is a fast-growing research area and the most outstanding results are highlighted. 相似文献