ESR spectra of spacered copper(II) dimers of 5-bromo-2-hydroxyacetophenone acyldihydrazones based on aliphatic dicarboxylic acids

Binuclear copper(II) complexes with 5-bromo-2-hydroxyacetophenone acyldihydrazones (H₄L) with the composition [Cu₂L·nPy] where the coordination polyhedra are linked by polymethylene chains with different lengths (from one to five units) have been synthesized and studied. The ESR spectrum of a polycrystalline sample of a complex based on malonyldihydrazone contains a major signal (g = 2.11) together with a weak signal corresponding to the forbidden transition (ΔM _S = 2, g = 4.18). At room temperature, ESR spectra of solutions of complexes of acyldihydrazones based on malonic, succinic, glutaric, and adipic acids contain seven HFS lines from two equivalent copper nuclei. These lines result from weak spin-spin exchange interaction between two unpaired electrons with the constant (36–38)·10⁻⁴ cm⁻¹. An increase in the polymethylene chain length to five units prevents the exchange interactions, and the ESR spectrum of a complex of the acyldihydrazone based on pimelic acid contains a signal of four HFS lines (a _Cu = 69.5·10⁻⁴ cm⁻¹), which is common to the monomeric copper(II) compounds. In the parallel orientation, the ESR spectrum of a frozen solution of the complex of malonyldihydrazone contained the superposition of signals due to fine and hyperfine structures with similar constants (D _∥ = 0.0074 cm⁻¹, A _∥ = 0.0070 cm⁻¹, g _∥ = 2.089, g _⊥ = 2.053). __________ Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1752–1757, August, 2005.     

Oxidative polymerization of anilinium 5-sulfosalicylate with peroxydisulfate in water

Anilinium 5-sulfosalicylate was prepared and characterized by elemental analysis, and FTIR and NMR spectroscopies. It was polymerized in an aqueous solution using ammonium peroxydisulfate as an oxidant. The precipitated polyaniline 5-sulfosalicylate exhibited high thermal stability and conductivity of 0.13 S cm⁻¹. Its mass-average molar mass and polydispersity index were determined by gel-permeation chromatography as 22,900 g mol⁻¹ and 2.7, respectively. Elemental analysis and FTIR spectroscopy study of polyaniline 5-sulfosalicylate revealed the doping level and the oxidation state between emeraldine and protoemeraldine salt while corresponding studies of the polyaniline base indicate a small extent of the covalent bonding of 5-sulfosalicylate anions to polyaniline chains.     

Acrylic copolymer membranes with proton conductivity

This work presents the results of a study of acrylic copolymer films from aqueous and nonaqueous media. Films prepared from aqueous emulsions possess good physico-mechanical properties, are optically transparent, and are chemically resistant to concentrated solutions of acids and bases. They may also be safely heated to a temperature of 333 K. Charge transport occurs through ion exchange, and film conductivity is 1 × 10⁻³ S cm⁻¹ at 298 K and 50% humidity. Acrylic copolymer films prepared from nonaqueous media (toluene, benzene, isopropyl acetate) exhibit a conductivity of 5 × 10⁻³ S cm⁻¹ at 298 K and 50% humidity, and modifying agents can be added to increase conductivity to 5 × 10⁻² S cm⁻¹.     

Effect of Al doping on the conductivity type inversion and electro-optical properties of SnO2 thin films synthesized by sol-gel technique

Al doped SnO₂ thin films have been synthesized by a sol-gel dip coating technique with different percentages of Al on glass and silicon substrates. X-ray diffraction studies confirmed the proper phase formation in the films and atomic percentage of aluminium doping in the films was obtained by energy dispersive X-ray studies. SEM studies showed the particle sizes lying in the range 100–150 nm for the undoped films and it decreased with increase of Al doping. Optical transmittance spectra of the films showed high transparency (∼80%) in the visible region and the transparency increases with the increase of Al doping in the films. The direct allowed bandgap of the films have been measured for different Al concentration and they lie within the range of 3.87–4.21 eV. FTIR studies depicted the presence of Sn–O, Al–O, bonding within the films. The room temperature electrical conductivities of the films are obtained in the range of 0.21 S cm⁻¹ to 1.36 S cm⁻¹ for variation of Al doping in the films 2.31–18.56%. Room temperature Seebeck coefficients, S_RT of the films were found in the range +56.0 μVK⁻¹ to −23.3 μVK⁻¹ for variation of Al doping in the films 18.56–8.16%. It is observed that the Seebeck coefficient changes its sign at 12.05% of Al in the films indicating that below 12.05% of Al doping, SnO₂:Al behaves as an n-type material and above this percentage it is a p-type material.     

Conductive polymers as a new type of thermoelectric material

Thermoelectric properties were investigated for the films of electrically conductive doped polyanilines. The thermoelectric performance, evaluated by thermoelectric figure-of-merit (ZT = T (S² σ) / κ), of various protonic acid-doped polyaniline bulk films was found to depend on the electrical conductivity σ of the film. Thus, the higher the electrical conductivity, the higher the figure-of-merit is, because the thermal conductivity κ of polyaniline films does not depend on the electrical conductivity. Among the conductive bulk films of polyaniline, the highest figure-of-merit (ZT = 1 × 10⁻⁴) was observed for (±)-10-camphorsulfonic acid (CSA)-doped polyaniline in an emeraldine form (σ - 188 S cm⁻¹) at room temperature. The multilayered film, composed of electrically insulating emeraldine base layers and electrically conducting CSA-doped emeraldine salt layers, exhibited 6 times higher ZT at 300 K than that of a bulk film of CAS-doped polyaniline, showing the highest ZT value of 1.1 × 10⁻² at 423 K. Stretching of the CAS-doped polyaniline film also increased the figure-of-merit of doped polyaniline films along the direction of the stretching.     

Conductivity of flowing polyaniline suspensions in electric field

The formation of chain structures by polarized polyaniline (PANI) particles suspended in silicone oil in the electric field has been monitored by recording suspension conductivity in the course of time. For that purpose, three types of PANI particles differing in the conductivity (3.1 × 10⁻³, 1.7 × 10⁻¹, and 2.0 × 10⁻¹ S cm⁻¹) have been chosen out of a series of nine samples prepared by controlled protonation of PANI base in orthophosphoric acid solutions. Relaxation times reflecting this process and characterizing the rate of the response to the electric field decreased with particle conductivity, indicating a higher polarizability of particles. At the same time, the maximum conductivity of suspension increased as a consequence of the electric and shear forces acting on the particles. In the shear fields, shorter relaxation times appeared than at rest. The simultaneous measurement of the shear stress confirmed that the conductivity investigation can reliably characterize the development of electrorheological structures.     

Application of chitosan/iota-carrageenan polymer electrolytes in electrical double layer capacitor (EDLC)

In this work, a chitosan/iota (ι)-carrageenan blended film doped with orthophosphoric acid (H₃PO₄) as ionic dopant and poly(ethylene glycol) (PEG) as plasticizer has been used as a separator and electrolyte in an electrical double layer capacitor (EDLC). A set of samples were prepared by the solution cast technique to see the effect of the different weight ratios of the proton donor and plasticizer on the conductivity. The highest conducting sample has composition 37.50 wt.% chitosan–37.50 wt.% ι-carrageenan–18.75 wt.% H₃PO₄–6.25 wt.% PEG. The conductivity value is 6.29 × 10⁻⁴ S cm⁻¹. The conductivity–temperature relationship is Arrhenian, and the activation energy for the highest conducting sample is 0.09 eV. The specific discharge capacitance of the EDLC is 35 F g⁻¹ at 0.11 mA cm⁻² current drain and was constant for 30 cycles.     

Spacered dinuclear copper(<Emphasis Type="SmallCaps">II</Emphasis>) complexes with acyldihydrazones of aliphatic dicarboxylic acids and 2-hydroxy-5-nitroacetophenone

Dinuclear copper(II) complexes with acyldihydrazones of 2-hydroxy-5-nitroacetophenone (H₄L) of the composition Cu₂(Py)_xL·mEtOH were synthesized and characterized. In these complexes, the coordination polyhedra of the copper atoms are linked to each other by a polymethylene chain of different lengths, from one to five monomer units. The structure of the [Cu₂L·4Mrf] complex (Mrf is morpholine) based on acyldihydrazone of malonic acid was established by X-ray diffraction. The copper(II) atoms in this complex are [4+1]-coordinated and are spaced by 6.94 Å. At room temperature, the signal in the ESR spectra of solutions of the complexes based on acyldihydrazones of malonic, succinic, glutaric, and adipic acids has a seven-line hyperfine structure with the constant of (35.3–38.8)·10⁻⁴ cm⁻¹ (g = 2.109–2.112) due to exchange interactions between unpaired electrons and two equivalent copper nuclei. An increase in the length of the polymethylene chain to five monomer units hinders exchange interactions, and the ESR signal of the complex based on acyldihydrazone of pimelic acid has a four-line hyperfine structure with a _Cu = 72.7·10⁻⁴ cm⁻¹ typical of mononuclear copper(II) complexes. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 229–234, February, 2007.     

The parathiocyanogen electrode

Stable, yellow anodic films of parathiocyanogen (SCN) _x were formed on a platinum electrode from 2.8 M KSCN in methanol at 45 °C at a constant current of 20–40 mA cm⁻² for 15–30 min. Loosely bound orange crystals of a more amorphous character were removed by rinsing to leave an adherent yellow film with sharp Raman bands under 647.1 nm laser excitation at 627 cm⁻¹ (vCS), 1152 cm⁻¹ and 1236–1261 cm⁻¹ (vNN and vCN). The lack of electroactivity and short-lived photocurrents pointed to an insulating film at potentials up to 1.0 V (SHE). At more positive potentials, longer-lasting photocurrents were obtained, consistent with breakdown of the insulating film. XPS scans confirmed N:C:S ratios close to 1:1:1, with a deficiency of S of some 10% due to S lost as sulfate at the film surface. Oxidation of SeCN⁻ in neutral aqueous solution led to the formation of a less-stable orange paraselenocyanogen film with a Raman band at 1256–1267 cm⁻¹, which decomposed within a day to grey selenium. Received: 12 December 1997 / Accepted: 23 March 1998     

Sulfurization of polymers

Polyethylene is exhaustively sulfurized by elemental sulfur at 160–365 °C to release hydrogen sulfide and form black lustrous powders (sulfur content ≈80%) that possess electric conductivity (10⁻⁶–10⁻⁸ S cm⁻¹ when doped with I₂). Elemental analysis data, IR spectra, X-ray patterns, DSC-TGA. derivatographic data, electric conductivity, and mass spectrometric characteristics of the polymers synthesized suggest the presence of fused polythienothiophene and polynaphthothienothiophene blocks in the polymers. For Part 1, see Ref. 1 Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 865–871, May, 2000.     

Effects of pH on electrocatalytic activity of functionalized carbon nanotubes

In this study, we modified carbon nanotubes (CNTs) by grafting with poly(ethylene glycol) (PEG) using the “grafting to” method. The PEG-grafted CNT (CNT-g-PEG) was cast on indium tin oxide (ITO) electrode to investigate the electrocatalytic activity of CNT to the redox reactions of the Fe(CN)₆^3−/4−as a probe using cyclic voltammetry and electrochemical impedance spectroscopy. The electrocatalytic activity of CNT was correlated with CNT dispersion in the cast film on ITO as a function of pH of aqueous solution from which the film was cast. The CNT dispersions in aqueous solutions of different pH and in the cast films were examined by visual observation and zeta potential, scanning electron microscopy and transmission electron microscopy, respectively. At a pH in the range of 3–11 at which ITO electrode was modified, two functionalized CNT (fCNT and CNT-g-PEG) were both found to electrocatalyze the redox reactions of the Fe(CN)₆^3−/4−probe and the PEG grafts in CNT-g-PEG could help CNT adhere to the electrode to obtain durable modified electrode. The more uniform CNT dispersions in aqueous solutions and in the cast films appeared to have greater electrocatalytic acitivity.     

Comparison of the hole mobility in undoped and boron-doped polycrystalline CVD diamond films

The drift mobility of nonequilibrium holes injected in undoped polycrystalline diamond films was determined, by a transit-time technique, as ca. 10⁻³ cm²/(V s). This hole mobility is three orders of magnitude lower than the “equilibrium” mobility in boron-doped diamond films [0.1–1 cm²/(V s)], determined from the films' dc conductivity. This difference is explained by the effect of a nonequilibrium charge carrier trapping during the carrier transport in polycrystalline diamond. Received: 3 December 1997 / Accepted: 9 April 1998     

Effect of ionic conductivity of a PAN–PC–LiClO<Subscript>4</Subscript> solid polymeric electrolyte on the performance of a TiO<Subscript>2</Subscript> photoelectrochemical cell

A nanoparticle TiO₂ solid-state photoelectrochemical cell has been fabricated. The effect of ionic conductivity of a solid electrolyte of polyacrylonitrile (PAN)–propylene carbonate (PC)–lithium perchlorate (LiClO₄) on the performance of a photoelectrochemical cell of indium tin oxide (ITO)/TiO₂/PAN–PC–LiClO₄/graphite has been investigated. A nanoparticle TiO₂ film was deposited onto ITO-covered glass substrate by controlled hydrolysis technique. A solid electrolyte of PAN–LiClO₄ with PC plasticizer prepared by solution casting technique was used as a redox couple medium. The room temperature conductivity of the electrolyte was determined by AC impedance spectroscopy technique. A graphite electrode was prepared onto a glass slide by electron beam evaporation technique. The device shows a photovoltaic effect under illumination. The short-circuit current density, J _sc, and open-circuit voltage, V _oc, vary with the conductivity of the electrolyte. The highest J _sc of 2.82 μA cm⁻² and V _oc of 0.56 V were obtained at the conductivity of 4.2 × 10⁻⁴ Scm⁻¹ and at the intensity of 100 mW cm⁻².     

Sulfurization of polymers

Polydiethylsiloxane reacts with elemental sulfur at 300–320 °C (ZnCl₂ slightly accelerates the process) with evolution of hydrogen sulfide and formation of black lustrous paramagnetic powders (sulfur content up to 38.50%), which possess a noticeable electric conductivity (3.20·10⁻⁷ S cm⁻¹ when doped with I₂) and redox properties. Polydimethylsiloxanes are stable under the same conditions. In rechargeable lithium batteries, the sulfurized polydiethylsiloxane behaves as an active cathode material allowing charging and discharging of the battery. The specific capacities of the cathodic and anodic processes (80–100 (mA h) g⁻¹) change insignificantly. The hydrolytic stability, elemental analysis, IR and ESR spectra, DSC-TGA and derivatographic analyses data, the electric conductivity, and the character of the electrochemical activity of the polymers synthesized indicate that the polymers contain the polyvinylene disulfide blocks cross-linked by the polysiloxane chain.     

The kinetics of chemical reactions in the products of dissociation of the CO2−H2 gas mixture in microwave discharge

The yields of hydrogen atoms, oxygen atoms and molecules, and hydroxyl radicals after a microwave discharge in the mixture of CO₂ and H₂ were measured by ESR spectroscopy in a flow-type system. A mathematical model of the kinetics of chemical reactions downstream the microwave discharge was devised. The concentrations of particles that cannot be detected under our experimental conditions were estimated. Experimental values of the concentration sensitivity for an RE-1306 ESR spectrometer are as follows: for a pressure of 1 Torr and optimized detection conditions, H^., 10¹¹ cm⁻³; O^., 3·10¹⁰ cm⁻³; OH^., 10¹⁰ cm⁻³; O₂, 3·10¹³ cm⁻³ (Ref. 7); for a pressure of 2 Torr, H^., 5·10¹² cm⁻³; O^., 2·10¹² cm⁻³; OH^., 2.5·10¹¹ cm⁻³; O₂, 7.5·10¹⁴ cm^{−3 8} Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 4, pp. 665–669, April, 2000.     

Chemical oxidative polymerization of dianilinium 5-sulfosalicylate

Dianilinium 5-sulfosalicylate was prepared in situ and then oxidized in aqueous solution with ammonium peroxydisulfate. The precipitated polyaniline 5-sulfosalicylate was soluble in polar aprotic solvents and showed conductivity of ∼0.1 S cm⁻¹. Scanning electron microscopy revealed the coexistence of nanorods and granular morphology of the polyaniline 5-sulfosalicylate. The weight-average molecular weight and poly-dispersity index were determined by gel-permeation chromatography as 53000 and 9.0, respectively. FTIR spectroscopic analysis combined with AM1 and MNDO-PM3 semi-empirical quantum chemical studies of the polymerization mechanism indicate both covalent and ionic bonding of sulfosalicylate to polyaniline chains. Raman spectroscopy proved the presence of substituted phenazine structural units besides ordinary emeraldine segments. The text was submitted by the authors in English.     

Rubidium-cationic conductance in the systems Rb2 ? 2xAl2 ? xAxO4 (A = P, V)

RbAlO₂-based solid solutions are synthesized in the systems Rb_{2 − x} Al_{2 − x} A _x O₄ (A = P, V). Temperature and concentration dependences of their conductance are studied; the rubidium-cationic character of the conductance is corroborated. The high ionic conductivity of the synthesized phases (∼5 × 10⁻³ S cm⁻¹ at 300°C, ∼2 × 10⁻² S cm⁻¹ at 700°C) is caused by (a) formation of rubidium vacancies as a result of the replacing of Al³⁺ ions by fivefold-charged cations of phosphorus or vanadium and (b) disordered crystal structure of γ-KAlO₂ type. The obtained data are compared with the results of the studying of similar systems. Original Russian Text ? G.Sh. Shekhtman, E.I. Volegova, E.I. Burmakin, 2009, published in Elektrokhimiya, 2009, Vol. 45, No. 4, pp. 495–499.     

Effect of dioxygen on ESR spectra of polyaniline

The effect of dioxygen on the width of ESR lines of powders and films of polyaniline was studied at 15–300 K. It was found that the line broadening can decrease or increase, which corresponds to strong or weak exchange, respectively. For dry polyaniline powders and films, maxdimum broadening was observed at 240 K. The findings were explained by spin exchange during collisions of a mobile polaron with immobile O₂ molecules bound to the polymer. The values of exchange interaction between the O₂ molecule and the polaron and the mobility of the polarons along the polymer chain were found. The mobility of polarons along the polymer chains decreases in the presence of H₂O, and dioxygen predominantly adds to the imine N atom. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2293–2297, December, 1999.     

Modeling Ar and Kr matrix effect on the ν s (Cl–H) and ν l (Cl–H) of Cl–H···NH3 by the IEF-PCM method

Ar and Kr matrix effect on the geometry and Cl–H stretching (ν _s (Cl–H)) and librational (ν _l (Cl–H)) frequencies of the hydrogen-bonded complex Cl–H···NH₃ are simulated within the framework of polarizable continuum model with integral equation formalism (IEF-PCM) at B3LYP and MP2 levels of theory with the basis set 6-311++G(2df,2pd). Within the framework of B3LYP and IEF-PCM, the simulated gas phase, Ar, and Kr matrix ν _s (Cl–H) of the complex are 2140, 1684, and 1550 cm⁻¹, respectively, which deviate from the experimental values (~2200, 1371, and 1218 cm⁻¹) by −60, 313, and 332 cm⁻¹. Within the framework of MP2 and IEF-PCM, the gas phase, Ar, and Kr matrix ν _s (Cl–H) are calculated as 2366, 2037, and 1957 cm⁻¹ by the harmonic approximation, and as 2177, 1876, and 1665 cm⁻¹ by the full-dimensional anharmonic correction. The matrix effect modeling is of greater importance than the anharmonic correction in accounting for the large experimental gas phase to Ar or Kr matrix shift of the ν _s (Cl–H) (−829 or −982 cm⁻¹). Our calculations do not support the assignment of the 733.8 and 736.9 cm⁻¹ bands to the Ar and Kr matrix ν _l (Cl–H).     

Hydrothermal syntheses and crystal structures of two CuI coordination polymers: [CuI(TATP)(CN)] n and [CuI(bpy)(SCN)] n (TATP = 1,4,8,9-tetranitrogen-trisphene, bpy = 2,2′-bipyridine)

Two new Cu^I coordination polymers, [Cu^I(TATP) (CN)] _n (1) and [Cu^I(bpy)(SCN)] _n (2) (TATP = 1,4,8,9-tetranitrogen-trisphene, bpy = 2,2′-bipyiridine), have been synthesized under hydrothermal conditions and structurally characterized by elemental analysis, IR, and X-ray crystallography. In 1 and 2, the metal centers are linked by bridging CN⁻/SCN⁻ to form one-dimensional chains in the crystals and are stabilized by interchain π–π stacking interaction.