Thermal and temperature dependence of electrical conductivity studies on Zn,Cd and Hg hydrazone complexes

The complexes of Zn, Cd and Hg of isatin isonicotinoyl hydrazone were prepared at two differentpHs. Their thermal studies (TG, DTG and DTA) have been made and the DC electrical conductivity of compressed powder samples as a function of temperature was investigated. The activation energies (E) were calculated for the ligand and the complexes which showed that the ligand has a lower value of E than the complexes. The magnitude of E was found to be affected by the nature of the metal and thepH of preparation.

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Zusammenfassung Bei zwei verschiedenenpH-Werten wurden die Zn-, Cd- und Hg-Komplexe von Isatinisonicotinoylhydrazon hergestellt. Diese wurden thermisch untersucht (TG, DTG, DTA) und die Gleichstromleitfähigkeit von gepreßten Pulverproben als eine Funktion der Temperatur untersucht. Sowohl für die Liganden als auch für die Komplexe wurden die Aktivierungsenergien (E) berechnet, wobei sich für die Liganden niedrigere Werte ergaben. Man fand, daß die Größe von E durch die Art des Metalles und denpH-Wert bei der Herstellung beeinflußt wird.

     

Electrical conductivity of some phenylthiopyridine complexes

Summary The electrical conductivity of some metal complexes of the compositionLM andLM ₂ (L: phenylthiopyridine derivative;M: Co(II), Ni(II), or Cu(II)) was measured in the temperature range 298–430 K. The activation energy of the conduction process, charge carrier density and mobility were calculated. The structure of the complexes is discussed on the basis of the results of conductometric titration and electronic and infrared spectra. The formation of four-coordinate complexes is concluded.

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Elektrische Leitfähigkeit einiger Phenylthiopyridinkomplexe

Zusammenfassung Die elektrische Leitfähigkeit einiger Metallkomplexe der ZusammensetzungLM undLM ₂ (L: Phenylthiopyridinderivat;M: Co(II), Ni(II) oder Cu(II)) wurde im Temperaturbereich von 298 bis 430 K gemessen. Die Aktivierungsenergie des Leitungsprozesses, die Ladungsträgerdichte und die Beweglichkeit der Ladungsträger wurden berechnet. Die Struktur der Komplexe wird auf der Grundlage der Ergebnisse von konduktometrischen Titrationen und UV/Vis- und IR-Spektren diskutiert. Es wird auf die Bildung vierfach koordinierter Komplexe geschlossen.

     

Thermal and electrical conductivity properties of some CrIII, MnII and UO 2 II amino alcohol complexes

Cr^III, Mn^II and UO₂ ^II amino alcohol complexes were prepared and analyzed. The IR spectra proved that the ligation occurs via oxygen and nitrogen atoms. The nujol mull electronic absorption spectra joined with the room temperature magnetic moment values proved that the complexes are of O_h geometry. The thermal behaviour of the complexes was studied by DTA and TG techniques. The mechanism of the decomposition was suggested. The thermodynamic parameters of the decomposition were evaluated and discussed. The entropy of activation changes, S*, showed that the transition states are more ordered than the reacting complexes. The D.C. electrical conductivity measurements of Cr- and Mn-amino alcohol complexes are of semiconductor behaviour. Empirical equations were deduced for the conduction of the investigated complexes.This revised version was published online in November 2005 with corrections to the Cover Date.     

Electrical conductivity of heat treated polyacrylonitrile and its copper halide complexes

The electrical conductivity of polyacrylonitrile homopolymer and polymer complexes of acrylonitrile (PAN) with CuCl₂, CuBr₂, and Cul₂ was measured at different temperatures. It was found that the electrical conductivity increased with temperature. Cyclic voltammetry was used for measuring the shift of the reduction peaks upon heat treatment of the polymer complexes. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 3057–3062, 1999     

Conductometric and DSC evidence for a high temperature phase transition in cobalt dibromide

A solid-state phase transition in cobalt dibromide at 647 K has been revealed by three different alternative current techniques. A small thermal effect of (181±18) J mol⁻¹ corresponding to the enthalpy of the transition has been determined by differential scanning calorimetry. The effect was observed on cooling and on heating as well.     

Thermal decompositions of some divalent transition metal complexes of triethanolamine

The thermal behaviours of the Ti(II), Mn(II), Fe(II), Ni(II), Cu(II) and Zn(II) complexes of triethanolamine were studied by means of thermogravimetry, differential thermogravimetry, differential thermal analysis infrared spectrophotometry and elemental analysis. The sequence of thermal stability of the metal complexes, determined by using the initial decomposition temperature, was found to be Ti(II)?Mn(II)>Fe(II)>Ni(II)>Zn(II)>Cu(II). Some of the kinetic parameters, such as the activation energy and order of reaction for the initial decomposition reaction, were calculated and the relationship between the thermal stability and the chemical structure of the complexes is discussed.     

Electrical and thermal studies on some acetylacetoneand benzoylacetone-arylhydrazones

The electrical and thermal properties of some acetylacetone-(I) and benzoylacetone-(II) arylhydrazone derivatives have been investigated. The results obtained show semiconductor behavior as evident from the positive temperature coefficient of electrical conductivity (dG/dT). Values of activation energy (ΔE) have been calculated in each case. The electrical conductivity increases with the introduction of either electron-donating or electron-withdrawing substituents to the phenyl ring. Differential thermal analysis curves showed sharp well-defined peaks at the melting point of the investigated compounds. The latent heats of fusion were calculated from these thermograms.     

Contributions on the Properties of Titanates with Ilmenite Structure. IV. The effect of an order-disorder transition on the high temperature electrical conductivity of NiTiO3

NiTiO₃ shows an order-disorder transition from an ordered ilmenite structure to a corundum structure at high temperatures. The transition is followed by a strong increase of the specific electrical conductivity. The conductivity was investigated as a function of temperature and oxygen activity. An order parameter according to common phase transition theories can be used to describe the behaviour of the conductivity in the transition region and vice versa. A model for the defect structure of NiTiO₃ is presented.     

Electrical conductivity of some hydrazones and binary complexes with transition metals

Summary The electrical behaviour of some hydrazones was studied in the temperature range of 290–435 K. The effect of complex formation with Mn(II), Fe(II), Co(II), Ni(II), and Cu(II) on the electrical conductivity of the hydrazones was investigated. The structure of the hydrazones was characterized using¹H and¹³C NMR spectroscopy. Conductometric titration and IR spectroscopy were used to illustrate the structure of the hydrazone complexes. Both the structures of the hydrazones and the complexation process play an effective role in the conduction process.

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Elektrische Leitfähigkeit einiger Hydrazone und ihrer binären Komplexe mit Übergangsmetallen

Zusammenfassung Das elektrische Verhalten einiger Hydrazone und ihrer Komplexe mit Mn(II), Fe(II), Co(II), Ni(II) und Cu(II) wurde im Temperaturbereich von 290 bis 435K untersucht. Die Strukturen der Hydrazone wurden mittels¹H- und¹³C-NMR-Spektroskopie charakterisiert, jene ihrer Komplexe durch konduktometrische Titration und IR-Spektroskopie. Sowohl die Strukturen der Hydrazone als auch der Komplexbildungsvorgang spielen eine wesentliche Rolle beim Leitungsvorgang.

     

Electrical conductivity measurements of hyaluronic acid and collagen

Electrical properties of hyaluronic acid (HYA) and collagen in the temperature range from –90°C (resp. –50°C for collagen) to 40°C are described. The value and type of electrical conductivity, temperature stability, and processes arising in the investigated samples during continual stress heating are determined by the measurements of temperature dependence of the electrical conductivity (both d.c. and a.c.).     

Pyridine-type complexes of transition metal halides

Formation of nitrogen ligated complexes of types NiL₆X₂, NiL₄X₂, NiL₂X₂ and NiL₁X₂ (whereL=pyridine, 2-, 3- and 4-methyl-pyridine andX=F, Cl, Br, I) have been studied by traditional preparative methods, i.e. from solutions and by solid-gas phase chemisorption. Quaternary mixed complexes were obtained by chemisorption from heated intermediates. The complexes thus formed were further analysed by simultaneous TG-DTG-DTA. Effects of the ligands on stoichiometry and thermal properties of the complexes are discussed.     

Thermal analysis study of some transition metal complexes by TG and DSC methods

The thermodynamic and thermal properties of [Cu(L)₂·Cl₂], [Ni(L)₂]·Cl₂, [Co(L)₂·Cl₂]; L=1,2-bis(o-aminophenoxy)ethane (BAFE), complexes have been investigated. The thermal decomposition of the complexes took place in two distinct steps in endothermic reaction up to 700°C. The activation energy E, the entropy change S ^#, enthalpy H change and Gibbs free energy change G ^# were calculated from the results of thermogravimetry analysis (TG) and heat capacity from the results of differential scanning calorimetry (DSC). It was found that the thermal stabilities and activation energies of the complexes follow the order Ni(II)>Cu(II)>Co(II) and E _Co<E _Ni<E _Cu, respectively.This revised version was published online in November 2005 with corrections to the Cover Date.     

NEB与过渡金属元素二元配合物的pH电位法研究

用精密pH电位法测定了在甲醇 水混合溶剂中配体氨三乙氧基三苯甲酸 (NEB)质子化常数 (2 5℃ ,I =0 .2 0mol·L- 1 NaCl) ,讨论了溶剂对质子化常数的影响 ,结果表明溶剂对质子化常数的影响呈线性关系。测定了NEB与部分过渡金属M(Ⅱ) (M =Cd、Co、Ni、Cu及Zn)二元配合物的稳定常数 ,实验数据处理用程序MINIQUAD - 82和MIQUV完成。在二元体系中存在的配合物物种有 112、111、110及 2 10型 (M2 + ∶NEB3- ∶H+ ) ,并且 111及 110型配合物稳定常数的变化规律Cd(Ⅱ) Zn(Ⅱ)符合Irving Williams序列     

Stereochemistry and structural phase transition of Cu(II) complexes containing orthophosphate ions and pyridine/picoline

Copper complexes of the type Cu(L)₄(H₂PO₄)₂ designated as complex (I), and Cu(L)₄ HPO₄ designated as complex (II), (whereL = pyridine (py) or λ-picoline (pic)) have been synthesised, characterised by chemical analyses, IR, and electronic and magnetic susceptibility data. From ESR studies it is concluded that complexes (I) have elongatedtrans octahedral stereochemistry. The temperature dependence of the ESR spectrum of Cu(py)₄(H₂PO₄)₂ suggests a fluxional behaviour in the immediate coordination of Cu(II), whereas very little variation of the ESR spectrum of the Cu(pic)₄(H₂PO₄)₂ complex indicates that the stereochemistry of this complex is essentially static in nature. The differential scanning calorimetric studies in the case of Cu(py)₄(H₂PO₄)₂ complex have given clear evidence for the occurrence of a structural phase transition at 147 K. The absence of any abrupt changes in the ESR spectrum at that temperature excludes the possibility of any changes in the immediate environment of Cu(II).     

Electrical conductivity of hexacene doped with iodine

Hexacene (HEX) and derivatives such as dihydrohexacene and dihydroxyhexcane quinone were synthesized and thin films of them were prepared by the sublimation method. The structure and conductivity of the films both before and after doping with iodine were studied. The doped HEX film showed the conductivity of 3 × 10^?2 S/cm at room temperature, which was lower than expected since the conductivity of highly ordered pentacene was above 100 Ω^?1 cm^?1. The reason for the low conductivity was considered to be the disorder in molecular alignment since the HEX film showed an amorphous structure. A reversible change in the conductivity of the HEX film was observed in air and in vacuum.     

Macromolecule–metal complexes exhibiting phase transition

A copolymer gel prepared from N-isopropyl-acrylamide (NIPA) and vinylferrocene (VF) exhibits volume phase transition. The phase transition can be controlled electrochemically, and electrochemical behavior of the gel can be controlled thermally. A copolymer of NIPA and VF, which is not crosslinked, also possesses similar characteristics. Those polymer and gel can be applied to enzyme electrodes. © 1997 John Wiley & Sons, Ltd.     

Metal complexes as phase transfer catalysts in the synthesis of O-acetylmandelonitrile

The asymmetric synthesis of O-acetylated mandelonitrile derivative was accomplished from PhCHO, KCN, and Ac₂O in a toluene--water system in the presence of transition metal complexes of Schiff"s bases as phase transfer catalysts.     

Electrical conductivity of cation-and anion-exchange membranes in ampholyte solutions

Several laws governing ampholyte transport through ion-exchange membranes are established by a comparative analysis of the concentration dependence of electrical conductivity for homogeneous (CMX, AMX) and heterogeneous (MK-40, MA-41) membranes in NaCl, LysHCl, and NaH₂PO₄ solutions. The increase in the electrical conductivity of membranes in ampholyte solutions as the solutions become more dilute is explained by the increased fraction of divalent ions of the amino acid (cation-exchange membrane) or from phosphoric acid (anion-exchange membrane) in the membrane as a result of Donnan exclusion of hydrolysis products (hydroxide ions or protons, respectively).     

Electrical conductivity enhancement of polyaniline by refluxing

The room temperature electrical conductivity of polyaniline (PANI) was found to increase remarkably after it was heated in tetrahydrofuran (THF) with refluxing for a certain period and then doped with methanesulfonic acid (MSA). The enhanced electrical conductivity of PANI was attributed to a partially cross‐linked network generated via the formation of new chemical bonds between adjacent PANI chain segments during thermal treating, which may shorten the inter‐chain distance and facilitate inter‐chain transition of charge carriers in doped PANI. During the refluxing, the moderate dissolving power for PANI as well as a much lower boiling point of THF were considered to have a unique effect on the formation of such partially cross‐linked network in PANI. As a comparison, PANI treated in poor solvents like methanol (or ethanol) and PANI treated in dimethyl formamide (DMF), which is a better solvent than THF but has higher boiling point, did not show an obviously increased electrical conductivity. Study on X‐ray diffraction (XRD) analysis of PANI after refluxing showed that crystallinity decreased gradually with the increase of cross‐linking degree, but the inter‐chain cross‐linking probably occurred first in crystalline region and then in the amorphous region. Electrical conductivity of PANI decreased after it was refluxed with THF for an extended period due to the decreased crystallinity and doping in PANI. Copyright © 2010 John Wiley & Sons, Ltd.     

Study of the thermal decomposition of cellulose-hyphan and its complexes with some transition and indium metal ions

The studied complexes formed by the chelating ion exchanger were characterized by reflectance and infrared spectrometry. The thermal degradation of pure cellulose-hyphan (CH) and its complexes with Hg²⁺, In³⁺, Cr³⁺, Mo⁴⁺ and Mn²⁺ under an atmosphere of air has been studied using thermal gravimetry (TG) and differential thermal analysis (DTG). The results showed that four different stages are accompanying the decomposition of (CH) and its complexes with the studied metals. These stages were found to be affected by the presence of the investigated metal ions. On the bases of the applicability of a non-isothermal kinetic equation it was found to be a first-order reaction with the rate of degradation,k, ranging from 8.3·10^?5 to 6.2·10^?3 for (CH) and from 1.7·10^?5 to 6.6·10^?3 s^?1 for its complexes. The activation energy,E _a, the entropy change, ΔS°, the enthalpy change, ΔH° and Gibbs free energy, ΔG° are calculated by applying the rate theory of the first-order reaction. The effect of the different central metal ions on the calculated thermodynamic parameters is discussed.