Thermal properties of zinc(II) chloroacetate and its complexes with nicotinamide and caffeine

Thermal decompositions of zinc(II) chloroacetate and its complexes with nicotinamide and caffeine were studied by means of TG/DTG, DTA, IR and mass spectroscopy. Thermal analysis showed that presence of the halogen significantly influenced the thermal decomposition. Decompositions may be characterized as two step reactions (release of nicotinamide or caffeine followed by pyrolysis of the carboxylate anion). Zinc chloride, CO, CO₂, CH₂O, ClCH₂CHO were found in gaseous products of the thermal decomposition.     

Monitoring of the Gas Phase Composition: A Prerequisite for Unravelling the Mechanism of Decomposition of Solids. Thermal decomposition of cobalt oxalate dihydrate

The complexity of the processes occurring during cobalt oxalate dihydrate (COD) decomposition indicates that an interpretation of the mechanism based only on the TG curve is of little value. Mass change alone does not allow deeper insight into all of the potential primary and secondary reactions that could occur. The observed mass changes (TG) and thermal effects (DTA/DSC) are a superposition of several phenomena and thus do not necessarily reflect COD decomposition alone. Investigation of the mechanism of decomposition requires the application of different simultaneous techniques that allow the qualitative and quantitative determination of the composition of the gaseous products. Composition of the solid and gaseous products of COD decomposition and heats of dehydration and oxalate decomposition were determined for inert, oxidizing and hydrogen-containing atmospheres. Contrary to previous suggestions about the mechanism of cobalt oxalate decomposition, the solid product formed during decomposition in helium contains not only metallic Co_met, but also a substantial amount of CoO (ca 13 mol%). In all atmospheres, the composition of the primary solid and gaseous products changes as a result of secondary gas-solid and gas-gas reactions, catalyzed by freshly formed Co_met. The course of the following reactions has been investigated under steady-state and transient conditions characteristic for COD decomposition: water gas shift, Fischer-Tropsch, CO disproportionation, CoO reduction by CO and H₂, Co_met oxidation under rich and lean oxygen conditions. This revised version was published online in August 2006 with corrections to the Cover Date.     

The functionality of the hybrid systems driven by molecular dimension of the guest copper Schiff‐base complexes entrapped in Zeolite‐Y

On encapsulation inside the supercage of zeolite‐Y planar Cu (II)–Schiff base complexes show the modified structural, optical and functional properties. The electronic effect of the different substituent groups present in the catalyst plays the decisive role towards their reactivity in the homogeneous phase but after the encapsulation in zeolite Y, reactivity is mainly governed by the molecular dimensions of the guest complexes rather than the electronic factor of the substituent groups attached on them. These systems are well characterized with the help of different characterization tools like XRD analysis, SEM ‐ EDX, AAS, FTIR, XPS, DSC, TGA, BET and UV–Visible spectroscopy and the comparative optical and catalytic studies have provided a rational explanation of enhanced reactivity of zeolite encapsulated metal complexes for various oxidation reactions compared to their corresponding solution states.     

Solid-phase thermal decomposition of polynuclear nickel(II) and cobalt(II) complexes

Solid-phase thermal decomposition of polynuclear Ni^II and Co^II pivalate complexes was studied by differential scanning calorimetry and thermogravimetry. The decomposition of the polynuclear (from bi-to hexanuclear) Co^II carboxylate complexes is accompanied by aggregation to form a volatile octanuclear complex. Thermolysis of the polynuclear NiII carboxylates results in their destructure, and the phase composition of the decomposition products is determined by the nature of coordinated ligands. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 250—260, February, 2006.     

Thermal oxidative destruction of complexes of heterocyclic N-oxides with Zn(II)tetra-phenylporphyrin

Thermogravimetry, differential thermal analysis and differential scanning calorimetry were applied for investigation of molecular complexes of heterocyclic N-oxide with zinc(II)tetraphenylporphyrin. The kinetic characteristics of the process of the thermal oxidative destruction for individual compounds and their molecular complexes have been calculated. The obtained results indicate that the complex formation of ZnTPhP with heteroaromatic N-oxides leads to an increase of the thermal stability both the metalloporphyrin and the ligands. It has been shown that the stability of the molecular complexes of ZnTPhP with heteroaromatic N-oxides depends on basicity of the coordinated ligand.     

Application of coupled TG-FTIR system in studies of thermal stability of manganese(II) complexes with amino acids.

Detailed thermal analysis of manganese(II) complexes with a-amino acids were carried out. The thermal degradation is multi-stage. Dehydration of complexes is the first mass loss step. Anhydrous compounds are unstable and decompose to Mn₃O₄ in air or to MnO in inert atmosphere. The intermediate solid products were identified by TG method and TG/FTIR combined technique. Among others solid residues, the presence of MnSO₄, MnBr₂ and Mn(CH₃COO)Cl was found. In the gaseous products of decomposition of organic ligand H₂O, NH₃, CO₂, CO, aromatic and non-aromatic hydrocarbons and very probably cyanoacetic acid and dimethyl sulfide occurred. Inorganic ions, i.e. Cl^-, Br^-or So₄ ^2-remain in the solid products of decomposition or are lost as HCl, HBr or SO₂. This revised version was published online in July 2006 with corrections to the Cover Date.     

Mechanism of thermal decomposition of thiourea derivatives

The thermal decomposition of a series of compounds has been studied by thermogravimetry, mass spectrometry, nuclear magnetic resonance and elemental analysis. The combined use of mass spectrometry and thermogravimetry (MS and TG) in the analysis of these compounds has allowed characterization of the fragmentation pattern which was the objective of this research. The gaseous products, volatile condensed products and solid residues were identified by NMR and MS. Based on the product of thermal decomposition, the mechanism of thermal decomposition has been derived.     

金属络合物制备分子筛负载金属催化剂的CO加氢反应性能

应用Ｙ分子筛吸附Ｆｅ（ＣＯ）５、Ｃｏ（ＣＯ）３ＮＯ和Ｍｏ（ＣＯ）６的温和热分解制备分子筛负载金属催化剂，从分子筛交换阳离子和吸附金属络合物之间的相互作用说明其ＣＯ加氢产物的分布特点。实验结果表明，分子筛内阳离子和吸附金属络合物间的相互作用显著影响制得催化剂的结构和反应的产物分布。由于金属络合物和分子筛内阳离子间的电子转移，使ＮｉＹ附载金属催化剂显示出高的ＣＯ转化率和甲烷选择性。在ＣｕＹ中，这种电子     

Studies on the Thermal Decompositions of Heteropolynuclear Glyoxylates of Cr(III) and Cu(II)

Complexes of Cr(III):Cu(II) with the glyoxylate dianion as ligand were synthesized in the range of cation atomic ratios (0.01–8):1.0. The results of non-isothermal analysis of the synthesized compounds correlated with the results of IR and UV-VIS spectroscopy, and gas chromatography of the volatile products of the decomposition allowed the formulation of a mechanism for the decomposition of the complex with Cr(III):Cu(II)=2:1 and the assumption that the other complexes are mixtures of this with the homopolynuclear complexes of Cr(III) and Cu(II), depending on the ratio of the cations Cr(III):Cu(II). The thermal conversion of the complexes takes place at relatively low temperatures, with partial transformation of the ligand into oxalate and of the oxide mixture into CuCrO₄. This revised version was published online in August 2006 with corrections to the Cover Date.     

Comparison on Thermal Decomposition of Propionate,Benzoate and Their Chloroderivative Salts of Zn(II)

The thermal decompositions of propionates, benzoates Zn(II), their chloroderivate and complexes with thiourea have been studied by the means of TG, DTG, DTA, IR and XRD-powder diffraction methods. The investigated decompositions are compared and the results are presented in this report. The results showed different features of thermal decomposition of Zn(II) halogenpropionate and halogenbenzoate. In the case of Zn(II) halogenpropionate the presence of halogen effects different features of thermal decomposition and changes character of the final products. In the case of halogenbenzoate Zn(II) the halogen does not influence neither the character of decomposition nor the character of final products. This revised version was published online in August 2006 with corrections to the Cover Date.     

Thermal Analysis in Structural Characterization of Hydrazone Ligands and Their Complexes

Results of our research on synthesis and characterization of complexes with acylhydrazone derivatives are described in this review paper. Structural characterization of newly synthesized complexes by thermal analysis (TG, DTA, DSC) is particularly emphasized in this paper. Thermal analysis enabled us to study not only structural changes of substances during thermal treatment, but also the mode of coordination and degree of deprotonation of acylhydrazones, as well as geometry of the coordination sphere of complexes, the structure of which had not been determined by X-ray analysis. Topics in this paper are as follows: complexes of dioxomolybdenum(VI) with tridentate hydrazones, usnic acid derivatives and their Cu(II) complexes, as well as transition metal complexes with 2,6-diacetylpyridine bis(hydrazones). This revised version was published online in July 2006 with corrections to the Cover Date.     

Reversed-phase ion-interaction chromatography of Cu(I)-cyanide complexes

It has been established that during the separation of Cu(I)-cyanide complexes, the cyanide:Cu(I) molar ratio, R of the eluted complex remained constant irrespective of the R value injected onto the column, and there was considerable tailing of the unretained cyanide peak and fronting of the Cu(I)-cyanide peak in an eluent containing no cyanide. The addition of small amounts of cyanide (100 μM) to the eluent resulted in the elimination of these effects on peak shape and a significant increase in the retention of the Cu(I)-cyanide species. These results suggested that more than one Cu(I)-cyanide complex may be present in the Cu(I)-cyanide peak in an eluent containing no cyanide. Three different detection systems [Fourier transform Infrared (FTIR) and photodiode array spectrophotometry and a post-column reaction (PCR)], were used to determine changes that occurred to the Cu(I)-cyanide complexes during the separation with eluents containing from 0 to 100 μM cyanide. The FTIR approach was unsuccessful due to a lack of sensitivity. The UV spectrum of the Cu(I) peak in any one eluent remained constant, irrespective of the composition of the injected sample, but there were distinct changes in this spectrum among eluents. Similarly, the R value of the Cu(I) peak determined by PCR remained the same in any one eluent but ranged from about 2.5 to about 3.4 for these eluents. The R value was found to vary within the eluted Cu(I)-cyanide peak, especially in an eluent containing no added cyanide. These results show that more than one Cu(I)-cyanide complex is present in the eluted peak and that in the absence of cyanide in the eluent, the eluted peak consists of a mixture of the di- and tricyano complexes of Cu(I).     

Asymmetric cyanohydrin synthesis using heterobimetallic catalysts obtained from titanium and vanadium complexes of chiral and achiral salen ligands

Titanium(IV)(salen) and vanadium(V)(salen) complexes are both known to form catalysts for asymmetric cyanohydrin synthesis. When a mixture of titanium and vanadium complexes derived from the same or different salen ligands is used for the asymmetric addition of trimethylsilyl cyanide to benzaldehyde, the absolute configuration of the product and level of asymmetric induction can only be explained by in situ formation of a catalytically active heterobimetallic complex, and is not consistent with two monometallic species acting cooperatively. Combined use of complexes containing chiral and achiral salen ligands demonstrates that during the asymmetry inducing step of the mechanism, the aldehyde is coordinated to the vanadium rather than the titanium ion. The titanium complexes also catalyse the asymmetric addition of ethyl cyanoformate to aldehydes, a reaction in which vanadium(V)(salen) complexes are not active. For this reaction, use of a mixture of titanium and vanadium(salen) complexes results in a complete loss of catalytic activity, a result which again can only be explained by in situ formation of a heterometallic complex. Both the titanium and vanadium based catalysts also induce the asymmetric addition of potassium cyanide/acetic anhydride to aldehydes. For this reaction, combined use of chiral and achiral complexes indicates that during the asymmetry inducing step of the mechanism, the aldehyde is coordinated to titanium rather than vanadium, a result which contrasts with the observed results when trimethylsilyl cyanide is used as the cyanide source.     

Spectrochemical and Thermal Behaviour of the 5-chloro-2-nitrobenzoates of Rare Earth Elements

The conditions of the formation of yttrium and lanthanide 5-chloro-2-nitrobenzoates were studied and their quantitative composition and solubilities in water at 298 K were determined. They are anhydrous or hydrated complexes and their solubilities are of the order of 10-3 mol dm-3. The IR and X-ray spectra for the complexes were recorded. All complexes are crystalline compounds. Their thermal decomposition was studied. It was found that on heating above 523 K the complexes decompose explosively. Therefore their thermal decomposition was carried out in the temperature range 273-523 K. Hydrated complexes lose crystallization water molecules in one step. From the results it appeared that during dehydration process no transformation of nitro group to nitrito took place. Some of physico-chemical properties of rare earth element 5-chloro-2-nitrobenzoates were compared with 2-nitro- and 3-chlorobenzoates of those elements. This revised version was published online in July 2006 with corrections to the Cover Date.     

Iron(III), cobalt(II) and copper(II) complexes bearing 8‐quinolinol encapsulated in zeolite?Y for the aerobic oxidation of styrene

A series of Fe(III), Co(II) and Cu(II) complexes of 8‐quinolinol were encapsulated into the supercages of zeolite? Y and characterized by X‐ray diffraction, SEM, N₂ adsorption/desorption, FT‐IR, UV–vis spectroscopy, elemental analysis, ICP‐AES and TG/DSC measurements. The encapsulation was achieved by a flexible ligand method in which the transition metal cations were first ion‐exchanged into zeolite Y and then complexed with 8‐quinolinol ligand. The metal‐exchanged zeolites, metal complexes encapsulated in zeolite–Y plus non‐encapsulated homogeneous counterparts were all screened as catalysts for the aerobic oxidation of styrene under mild conditions. It was found that the encapsulated complexes always showed better activity than their respective non‐encapsulated counterparts. Moreover, the encapsulated iron complex showed good recoverability without significant loss of activity and selectivity within successive runs. Heterogeneity test for this catalyst confirmed its high stability against leaching of active complex species into solution. Copyright © 2011 John Wiley & Sons, Ltd.     

CoPc在八面沸石笼中的原位合成及性能研究

采用苯酐－尿素路线，对CoPc金属配合物在八面沸石超笼中原位合成进行了考察，并采用多种物化手段和催化反应对所制备的CoPcY进行了详细的表征。结果表明，该制备路线是一简便有效的合成路线，采用该路线可在八面沸石超笼中原位合成CoPc金属配合物并将之固定于八面沸石中。在该制备方法中合成温度、离子交换所采用的盐类型及催化剂对CoPc金属配合物在八面沸石超笼中的合成及所制备的CoPcY在环己烷氧化反应中的催化性能有很大的影响，其中180 ℃为最佳合成温度，氯化钴较适合作为交换的盐类。在八面沸石超笼中原位合成的CoPc金属配合物在温和的反应条件下对环己烷氧化具有良好催化活性，转化数TON最高可达5 000以上。     

Use of Biopolymers for the Removal of Metal Ion Contaminants from Water

Summary: Naturally abundant biosorbants such as chitin and chitosan are recognized as excellent metal ligands, forming stable complexes with many metal ions, and serving as effective protein coagulating agents. Chitosan is a heteropolymer made of D-glucosamine and a small fraction of N-acetyl-D-glucosamine residues. Therefore, the adsorption ability of chitosan is found to be much higher than that of chitin, which has relatively fewer amino groups. Zeolites are crystalline microporous aluminosilicates with ion exchange properties suitable for a wide range of applications in catalysis and separation of liquid and gaseous mixtures. Incorporation in chitosan membranes is an effective method to control the diffusion outside the zeolite crystals and appropriately designed composite systems can find numerous opportunities for applications in wastewater treatment. In this paper we present the synthesis of zeolite-chitosan and zeolite-ethyl cellulose composites by encapsulation of clinoptilolite using a gelling solution of chitosan or an ethyl cellulose solution in ethyl acetate. The adsorption process of Cu²⁺ and Cd²⁺ on some adsorbents was investigated: clinoptillolite tuff (0.05 mm), chitosan flakes, ethyl cellulose, zeolite-chitosan and zeolite- ethyl cellulose composites. Zeolite-chitosan composites have been prepared by encapsulation of zeolites by a gelling solution of chitosan. Micrometric crystals of clinoptillolite were dispersed in a 3% chitosan solution in 1% aqueous acetic acid. The chitosan gel was formed and the zeolite crystals were encapsulated during the gelling process. The same procedure was used to obtain zeolite – ethyl cellulose composites. Study of the metal ion retention properties of different adsorbent materials was carried out using a steady state regime. The concentration of heavy metal ions in supernatant was determined by the atomic absorption spectrophotometric method. Adsorption isotherms of metal ions on adsorbents were determined and correlated with common isotherm equations such as Langmuir and Freundlich models.     

Zum thermischen Verhalten von Aluminiumfluoridhydroxidhydrat AlF2,3(OH)0,7(H2O)

The Thermal Behaviour of Aluminium Fluoridehydroxide Hydrate AlF_2.3(OH)_0.7(H₂O) The thermal decomposition of AlF_2,3(OH)_0,7(H₂O) depends strongly on the partial pressure of the gaseous reaction products and proceeds in three overlapping steps, namely dehydratation, formation of x-ray amorphous Al₂O₃ and metastable β-AlF₃, and formation of α-AlF₃ and α-Al₂O₃. Beside that an exchange of F/OH takes place. The vaporization is mainly determined by the crucible type and pressure conditions, as shown by simultaneous TG-MS measurements too. Main gaseous species are H₂O and HF. The gas complexes HAlF₄, and H₂AlF₅ are observed.     

Thermal Analysis of Manganese(II) Complexes With Glycine

The thermal decomposition behaviour of the manganese(II) complexes with glycine: Mn(gly)Cl₂(H₂O)₂, Mn(gly)₂Cl₂, Mn(gly)Br₂(H₂O)₂, Mn(gly)₂Br₂(H₂O)₂ was investigated by means of TG-DTG-DTA, Hi-Res-TA and DSC techniques. The evolved gas analysis was carried out by means of the coupled TG-FTIR system. Heating of the complexes results first in the release of water molecules. Next, the multi-stage decomposition process with degradation of glycine ligand occurs. Water, carbon dioxide and ammonia were detected in the gaseous products of the complexes decomposition. The temperature of NH₃ evolution from the complexes is higher than from free glycine. The final residue in the air atmosphere is Mn₂O₃ which transforms into Mn₃O₄ at 930°C. In a nitrogen atmosphere, the complexes decompose into MnO. This revised version was published online in August 2006 with corrections to the Cover Date.     

Factors influencing the thermal decomposition of transition metal complexes with 2-OH-aryloximes under nitrogen

Summary The thermal behavior of copper(II), nickel(II) and palladium(II) complexes with two anionic varieties of 2-OH-aryloximes (ox), [M(ox)₂] (2-hydroxypropiophenonoxime and 2-hydroxy-4-methoxy-benzophenonoxime) was studied by using simultaneous TG/DTG-DTA technique under nitrogen in the temperature range 40-700°C. The behavior was compared with that in static air, which had been previously studied. It was found that the metal, the substituents on the ligand and the heating rate influenced their thermal decomposition. The thermal stability of the complexes with the same ligand depended on the metallic cation, following the order Pd(II)>Ni(II)>Cu(II). It also depended on the type of ligand, increasing with bulky substituents on the oximic carbon and the benzene ring. The sample mass almost did not affect their decomposition mode. The residues at 700°C of all complexes consisted of a carbonaceous oxide, determined by energy dispersive spectrometry (EDS) and IR spectroscopy