Thermal Behaviour of Tin(II) Complex With 8-hydroxyquinolinate in the Solid State

Tin(II) complexes with 8-hydroxyquinolinate in solid state have been obtained by adding aqueous ammonium to a solution containing stannous chloride and 8-hydroxiquinoline in medium of HCl and acetone up to pH 5 and 9, respectively. The products obtained show the same composition, Sn(C₉H₆ON)₂; however there are some differences regarding both the thermal behaviour in an oxidant atmosphere and morphology. These products were characterised by elemental and complexometric analysis, TG and DTA curves, infrared and X-ray diffractometry. TG curves show, above 448 K, the partial oxidation on air atmosphere of Sn(II) complexes to Sn(IV) complexes, SnO(C₉H₆ON)₂. This behaviour does not depend only on pH in which the compounds were obtained but also on the heating rate in TG curves. Sn(II) complexes volatilise almost completely on nitrogen atmosphere and partially on air atmosphere depending on the oxidation degree of the compound. This revised version was published online in July 2006 with corrections to the Cover Date.     

TG,DTA and electrical conductance properties of some Cu(II) AND Mn(II) bisazo- dianils complexes

The TG and DTA of a new series of Mn(II) and Cu(II) complexes with a number of newly prepared bisazo-dianil ligands were studied in the temperature range (20-700°C). The TG and DTG curves display to main steps, the first one within the temperature range (25-330°C) correspond to the elimination of water or and ethanol from the complexes. The second step within the range (350-625°C) is due to the decomposition of the complexes yielding the metal oxides as the final product. The rate constants of the dehydration and decomposition reactions were determined, from which some kinetic parameters were evaluated. The DTA curves show that the dehydration of the metal complexes is an endothermic reaction. In all cases the anhydrous metal complexes undergo exothermic decomposition reactions to give the metal oxide. The thermodynamic parameters (ΔE, ΔH, ΔS, ΔG) for the occurring processes are calculated. The electrical conductivities of the solid complexes were measured and the activation energy of the complex and its free ligand are also calculated. This revised version was published online in August 2006 with corrections to the Cover Date.     

Electronic structure of molecular complexes in their ground and excited states. II.

Using a modified INDO method the potential energy curves for ground and some excited states (with an appreciable amount of charge transfer character) of wide range molecular complexes have been calculated. The calculation performed for CT, HB, CTTS, etc. systems shows that potential energy curves could be regarded as criterion for classification of molecular complexes into several groups with different properties. Analysis of proton motion in ground and excited states of H₃N-HCl and hydrogen maleate anion have also been performed.     

RE(III)与2-羰基丙酸水杨酰腙配合物的合成、表征及热化学

用2-羰基丙酸水杨酰腙与轻稀土硝酸盐反应, 合成了7种新的配合物. 经元素分析、化学分析及X射线粉末衍射等手段确定了其组成为RE(C10H9N2O4)(C10H8N2O4)•nH2O(RE＝La、Ce、Pr、Nd、Sm、Eu、Gd), 用红外、紫外、荧光光谱分析对以上配合物的结构进行了表征; 用微热量计测定了稀土芳酰腙配合物的溶解焓, 发现其溶解焓数据不随稀土原子序数单调变化, 而呈转折变化, 可认为呈稀土的四分组现象的前两组.     

Thermal decomposition of complexes of antimony(III) bromide with hydrobromides of some aromatic amines

Thermal studies have been carried out on crystalline complexes formed between antimony(III) bromide and hydrobromides of some aromatic amines in concentrated hydrobromic acid solutions. Thermal analysis curves of the compounds under study are presented. Kinetic parameters of the thermal decomposition reactions were calculated from the TG curves using the Horowitz—Metzger method. A comparison of the thermal stabilities of the complexes was made.     

Center of Gravity (COG) Method as a Tool in Processing of Voltammetric Signals

The center of gravity method (COG) was applied (for the first time) in voltammetry (polarography) as a tool for very precise determination of peak potentials, and signal shifts. Basically, the adjustment of the method consists of finding the optimal fraction of the peak that contains information about peak position, either of original signal or of its 1^st or 2^nd derivatives, along with optimal selection of parameters for Savitzky? Golay smoothing of original curves and elimination of baseline influence. The principle of the method and its validation were demonstrated and checked on simulated differential pulse polarograms (DPP) representing a series of curves for the determination of stability constants of labile metal complexes (DeFord‐Hume method). It was shown that COG outperforms the classical “one‐point” method (OPM) in precision and accuracy, providing excellent results even if a very large step potential (e.g. 10 mV) was used. The problems of reduced accuracy and precision in case of curved (non‐ideal) baseline and asymmetric peaks were successfully overcome by applying COG on curves transformed by 1^st and/or 2^nd derivatives. The method was additionally examined in details on a simple experimental dataset of cadmium chloride complexes in 4 mol dm^?3 ionic strength solution and on a more complex dataset of uranyl selenate complexes in 3 mol dm^?3 ionic strength solution. Stability constants obtained by COG agree well with those in the literature with much better precision than the classical one‐point method (checked by standard error of the fit).     

Thermal stability of ionene polymers

Two different cationic polymers of the same chemical type and with very similar chemical structures were reacted with a natural bentonite over a wide range of polymer/clay ratios. This study involved the synthesis of cationic aliphatic ammonium polyionenes, specifically 3,6-ionene and 3,6-dodecylionene. Ionenes are ion-containing polymers that contain quaternary nitrogen atoms in the main macromolecular chain as opposed to a pendant chain. The CHN content, basal spacing, and elemental composition of each of the polymer–clay complexes were analyzed by X-ray diffraction, X-ray fluorescence, and thermogravimetry. All the polycations reacted to form interlayer complexes with clay, which displaced more Na⁺ and little Ca²⁺. Sodium and calcium were both present as interlayer cations in the clay and its complexes. The TG/DTG curves show that both polymers underwent thermal degradation in more than one stage. Specifically, 3,6-ionene was found to undergo two stages of decomposition and 3,6-dodecylionene undergo three stages. The behavior of the TG/DTG curves and the activation energy values suggest that 3,6-dodecylionene (E = 174,85 kJ mol^?1) complexes have greater thermal stability than 3,6-ionene (E = 115,52 kJ mol^?1) complexes. The mechanism of degradation suggests a direct interaction with the dodecyl chain containing 12 carbons, which are present in 3,6-dodecylionene but not in 3,6-ionene.     

A Preliminary Investigation of the Solution Complexation of 4-Sulphonic calix[n]arenes with Testosterone

The complexation between water soluble calixarenes and testosterone has been studied. Stability constants of the host guest complexes of 4-sulphonic calix[n]arenes (n = 4, 6 and 8) with testosterone in water and buffers (pH 5.8, 7.3 and 10.0) were determined from phase solubility curves. These solubility curves indicated that the complexes were all of the A_L type. The constants were in the range 26–341 M^-1, dependent on the size of the calixarene and the pH of the solutions.     

A study of the chelation reaction of gallium and indium with Arsenazo 1

The chelation reactions of gallium and indium with Arsenazo 1, i.e., 3-[(o-arsonophenyl)azo]-4,5-dihydroxy-2,7-naphthalene disulfonic acid, have been studied in detail. The nature and number of complexes formed was studied and it was found that gallium and indium form only one complex with Arsenazo 1. The composition of the complexes formed was found by various methods and it was found that both the complexes have composition 1:1 (metal:reagent). The values of log K were calculated by different methods at four different fixed values of ionic strength. For both the complexes, the value of thermodynamic stability constant has been obtained by plotting values of log K against ionic strength and extrapolating the curves to zero ionic strength. A tentative suggestion about the structure of the chelate ring has been made. The studies were further extended to the analytical aspects of the complexes and a suitable procedure has been recommended for the spectrophotometric determination of gallium and indium using this reagent.     

Thermal Degradation Studies of Complexes of a Derivative of Phenhomazine (Dibenzo[b,f][1:5]diazocine‐6:12‐Dione (PHZD)) by Thermoanalytical Techniques

Some of the bis‐complexes of a derivative of phenhomazine (dibenzo[b,f][1:5]diazocine‐6:12‐dione; PHZD) with Ni(II), Cu(II), Co(II), Cd(II), Zn(II) and Hg(II) of the general formula M(PHZD)₂X₂ [where X = C1, Br and I], were prepared and identified. These complexes have been characterised on the basis of elemental analysis, and spectroscopic, magnetic and conductance data. The thermal mode of decomposition and thermal stability of these complexes was investigated on the basis of the respective thermal curves in a static air atmosphere. The thermoanalytical investigations indicate that these complexes undergo two‐step changes as temperature is raised, except for Cd(II) and Hg(II) complexes, with the formation of metal oxides as end product. The degradation mechanism of the complexes has also been proposed.     

Polarographic and spectrophotometric studies of the spiro[indolin-pyridobenzopyrane] complexes with the heavy metal ions

By means of the cathode differential pulse polarography on a mercury drop electrode the reactions of Zn²⁺, Cd²⁺, and Pb²+ ions with the spiro[pyridobenzopyranes] of the indoline series in DMSO were studied. Tetrabutylammonium perchlorate was used as the background electrolyte. It is found that well soluble heavy metal complexes of the spiro[indolin-pyridobenzopyranes] are formed in DMSO. The number of ligands, the step and the general stability constants of the obtained complex compounds are evaluated. The distribution curves of all the complexes under investigation are plotted. The spiropyrane complexes were also studied by means of the spectrophometric method. Good agreement of the results obtained by two different methods was established.     

Physicochemical Studies and Thermal Decomposition Kinetics of Co(II), Ni(II), Cu(II) and Zn(II) Complexes of Citronellal Anthranilic Acid

Cobalt(II), nickel(II), copper(II) and zinc(II) complexes of two new Schiff-bases, citronellal anthranilic acid and citronellal-5-bromoanthranilic acid have been synthesized. On the basis of spectral, magnetic and thermal data, octahedral structure was assigned to all complexes [ML₂(H₂O)₂]. Thermal decomposition of these complexes was studied by TG. Kinetic parameters, viz activation energy, E, pre-exponential factor, A, and order of reaction, n, were calculated from the TG curves using mechanistic and non-mechanistic integral equations. This revised version was published online in July 2006 with corrections to the Cover Date.     

Cadmium(II) binding by soil-derived fulvic acid measured by anodic stripping voltammetry

Titrations of aqueous solutions of soil fulvic acid (30, 45, and 60 mg l^-1) with cadmium ion solutions at pH 6 and 7 reveal unusual shapes in the stripping current (i_s) vs. total cadmium ion (C_cd²⁺) curves. The expected inflections occur in the titration curves at 8–16 μM. at pH 6 and 12–26 μM at pH 7. In addition, there is an initial rapid increase in i_s at very low C_cd²⁺. The initial rapid increase in current is attributed to labile cadmium—fulvic acid complexes that contribute to i_s by rapid dissociation. Subsequent addition of cadmium ion results in moderately labile complexes and i_s becomes partially kinetically controlled. The stripping current was corrected for kinetic current contributions from dissociation of complexes, and total ligand concentrations, conditional stability constants, and upper slopes were calculated from data well past the titration end-point. The use of upper slopes after kinetic current corrections as in situ calibration curves, allowed calculations of equilibrium cadmium concentrations. The data show that both kinetic current corrections and in situ calibration curves are necessary to avoid substantial errors in calculations of equilibrium cadmium concentrations from anodic stripping voltammetric experiments.     

Thermal studies of some mixed complexes of Mn(II) with picrate and nitrogen donors

The thermal decompositions of nine mixed ligand complexes of Mn(II) containing picrate and mono- or bidentate nitrogen ligands were studied by thermogravimetry. The kinetics of decomposition were examined by using the Coats-Redfern and Horowitz-Metzger equations; the decomposition was in all cases of the first order. The activation energies and other kinetic parameters were computed. The decomposition mechanisms exhibited a similar character for all the studied compounds. It was observed from the TG curves that the complexes decomposed to give six-coordinate intermediates, formed from substitution of the picrate into the inner coordination sphere. These intermediates decomposed to Mn(II) picrate and finally to Mn₂O₃.     

The thermochemical behaviour of zeolite inclusion complexes

The thermochemical behaviour of nitrate inclusion complexes of zeolites of type A was investigated and DTA curves recorded. An attempt was made to identify thermal effects. Supplementary information was obtained from the IR spectra of the solid phase before and after heating as well as from the process of denitration of inclusion complexes.     

Copolymerization of carbon dioxide and propylene oxide catalyzed by two kinds of bifunctional salen-cobalt(III) complexes bearing four quaternary ammonium salts

Two new bifunctional salen-cobalt(III) complexes were synthesized, which consist of salicylaldehyde bearing four quaternary ammonium salts and two different diamines. The copolymerization results indicated that decreasing temperature is advantageous for both the complexes. Of both the diamines, the complex 9 with o-diaminobenzene has a higher catalytic effect compared to complex 6 with 1,2-diaminocyclohexane. The catalytic effect of complex 9 is over 3.5 times than that of complex 6 at a temperature of 30°C. The research of P_CO2 on the copolymerization revealed that the first-rank pressure was at 2 MPa for the two complexes. The highest turnover number are under conditions of T = 30°C, P_CO2 = 2 MPa, and t = 24 hr. Differential scanning calorimeter curves indicated that poly(propylene carbonate) (PPC) by complex 9 has the highest Tg of 54.2°C. DTGA curves showed that there were two thermal degradation peaks, the first is for the ester bond, and the second is for the C–C bond.     

The 13C NMR spectra of π-arenechromium carbonyl complexes

The ¹³C NMR spectra of π-arenechromium complexes XC₆H₅Cr(CO)₂L (where I, L  CO; II, L  PPh₃; X  aliphatic and aromatic substituents) were investigated. The effect of the nature of the substituent X on the chemical shifts of the carbon atoms of the aromatic ring in these complexes was analyzed.It was established that a correlation exists between δ(¹³C) and σ_R (Taft's constant) in complexes I, not only for C(4) nuclei but also for C(3) metal atoms, the difference being that the slopes of the corresponding curves are opposite.     

Kinetics of the decay of nitroxyl radicals during polymerization of a complex of acrylamide with bismuth nitrate

Kinetics of the decay of nitroxyl radicals during spontaneous polymerization of complexes of acrylamide (AAm) with Bi^III nitrate has been studied by ESR. From a comparison of the experimental and calculated kinetic curves, the initiation rate constant of polymerization has been determined. The approach proposed is suitable for determining the main kinetic characteristics of other polymerizable nonparamagnetic AAm complexes with metal nitrates.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1572–1575, September, 1994.This work was carried out with the financial support of the Russian Foundation for Basic Research (Project No93-03-4162).     

Study on the long life radicals of hexanediol diacrylate in irradiated urea canal complexes in relation to post-polymerization by irradiation

The properties of radicals formed on irradiating long chain monomers in urea canal complexes were studied by ESR and related to the results of post-polymerzation. The initiating radicals (CH₃-?HCOOR) were trapped in canal complexes as a result of γ-irradiation at relatively high temperature such as 25° and the radicals converted to propagating radicals (～CH₂-?HOOR0 on heating to 70°. The temperature dependence of radical concentration was followed and the decay curves corresponded well with the results of post-polymerization.     

The adsorption of dopamine on gold and its interactions with iron(III) ions studied by microcantilevers

The adsorption of dopamine (DA) molecules on gold and their interactions with Fe³⁺ were studied by a microcantilever in a flow cell. The microcantilever bent toward the Au side with the adsorption of DA due to the change of surface stress induced by the intermolecular hydrogen bonds of DA or the charge transfer effect between adsorbates and the substrate. The interaction process between DA adsorbates and Fe³⁺ was revealed by the deflection curves of microcantilever. As indicated by the appearance of a variation during the decline of curves, two steps were observed in the curve at relative high concentrations of Fe³⁺. In this case, Fe³⁺ reacted with DA molecules only in the outer layers and the complexes removed with solution. Then Fe³⁺ reacted further with DA molecules forming the surface complex in the first layer next to the gold. At this stage, the stability of surface complexes was time dependent, i.e., unstable initially and stable finally. This may be due to the surface complexes change from mono-dentate to bi-dentate complexes. In another case, i.e., at relative low concentration of Fe³⁺, only the first step was observed as indicated by the absence of a variation. X-ray photoelectron spectroscopy (XPS) and cycling voltammetry (CV) results provided complementary evidence for the result of microcantilever and proposal. As low as 5 × 10⁻¹⁰ M Fe³⁺ was detected by DA modified microcantilever with a good selectivity over other common metal ions.