Structural and electrical properties of soluble conducting poly(3-pentylthiophene)

A solution of processible poly (3-pentylthiophene) (P3PT) was synthesized by chemical polymerization. The structure of the resulting polymer was investigated by gel permeation chromatography (GPC); infrared;¹H and¹³C nuclear magnetic resonance; Ultraviolet visible spectroscopy (UV-Vis) and wide-angle X-ray scattering (WAXS) techniques. It was found that the microstructure of the chains has a low number of irregular couplings and thus has desirable electrical properties. In the small-angle region of X-ray scattering, a pronounced peak was observed with ad (coherence length) value of 1.51 nm for P3PT and 1.835 nm for poly (3-heptylthiophene (P3Hept). Electron spin resonance measurements showed that P3PT has 10¹⁸ spins g^–1, ag value 2.0039, and a H _pp of about 6 Gauss. The Pauli-like susceptibility after doping P3PT with I₂ is of the same order as for poly paraphenylene (PPP) doped with AsF₅, and corresponds to a density of states at the Fermi level about 0.01 states eV^–1 per carbon atom in the thiophene ring. The current-voltage (I–V) characteristics obtained for different temperatures were always linear. The dark room temperature conductivity was 10^–8 Sm^–1 and distinctly increased after doping. The P3PT studied is a good candidate for potential commercial applications.     

Cyclic and Linear Structures of C13: A Computational Study

Recently, a linear structure of C₁₃ was observed and its infrared spectrum recorded. Computations of the linear and cyclic structures of C₁₃ are thus presented. The computations are performed at ab initio level using the standard 6-31G* basis set. Electron correlation is treated by density functional theory (Becke3LYP) and perturbation treatment (MP2=FC). With the density-functional approach the standard 6-311G* and 6-311G(2d,p) basis sets are applied, too. In all the treatments the cyclic structure (C_2v symmetry) is located about 90 kJ/mol below the linear form (D_∞h symmetry), while a tricyclic structure is considerably higher in energy (about 280 kJ/mol above the monocyclic species). Even at high temperatures the linear form represents less than 10% of the equilibrium isomeric mixture. Computed IR spectra are also reported. The stability evaluation corresponds to the findings of ion chromatography.     

Quantum-chemical model evaluations of thermodynamics and kinetics of oxygen atom additions to narrow nanotubes

This paper reports a computational study of oxygen additions to narrow nanotubes, a problem frequently studied with fullerenes. In fact, fullerene oxides were the first observed fullerene derivatives, and they have naturally attracted the attention of both experiment and theory. C60O had represented a long-standing case of experiment-theory disagreement, and there has been a similar problem with C60O2. The disagreement has been explained by kinetic rather than thermodynamic control. In this paper a similar computational approach is applied to narrow nanotubes. Recently, very narrow nanotubes have been observed with a diameter of 5 A and even with a diameter of 4 A. It has been supposed that the narrow nanotubes are closed by fragments of small fullerenes like C36 or C20. In this report we perform calculations for oxygen additions to such model nanotubes capped by fragments of D2d C36, D4d C32, and Ih C20 fullerenic cages (though the computational models have to be rather short). The three models have the following carbon contents: C84, C80, and C80. Both thermodynamic enthalpy changes and kinetic activation barriers for oxygen addition to six selected bonds are computed and analyzed. The lowest isomer (thermodynamically the most stable) is never of the 6/6 type, that is, the enthalpically favored structures are produced by oxygen additions to the nanotube tips. Interestingly enough, the lowest energy isomer has, for the D2d C36 and D4d C32 cases, the lowest kinetic activation barrier as well.     

One-, Two- and Three-Dimensional Structures of C20

The aggregates C₂₀ have been studied by the AM1 quantum-chemical method and at least three different local energy minima found. The located planar cyclic ground state exhibits C_10h symmetry, being followed by two triplet linear structures, a spheroidal C₁ structure, and a bowl-shaped C_5v structure.     

Katalytische und elektrochemische Aktivität einiger Metall-Polyphthalocyanine

The catalytic properties of Fe, Co, Cu, Ni and Mg polyphthalocyanines in the reaction of hydrogen peroxide decomposition and their electrochemical properties in the reaction of oxygen reduction have been investigated. The accordance of the orders of catalytic and electrochemical activities of the investigated metallic polyphthalocyanines has been stated. The influence of reaction environment on catalytic and electrochemical activities also has been found. It has been established, that the linear dependence between reaction rate constant of hydrogen peroxide and its electrical conductivity, for iron polyphthalocyanine soluble in concentrated sulphuric acid can be observed.     

A class of robust edge detectors based on latin squares

The theory of Latin Square experimental designs is extended to edge detection of multi-grey level pictorial data. Latin Square designs are realized using mask operations either as a square or in linear forms using ANOVA to estimate the model parameters. The test statistics are based upon the robust F-test and the thresholds are selected by an empirical interactive process. A post hoc comparison method is used to confine the edge element ambiguities to 2-pixel layer thickness in masks greater than 2 × 2 × k. Computer simulations are shown to verify the theory.     

Computations on Metallofullerenes Derivatized during Extraction: La@C80-C6H3Cl2 and La@C82-C6H3Cl2

Recently, an extraction of la metallofullerenes from soot using 1,2,4-trichlorobenzene has been reported for La@C₈₀ and La@C₈₂. In both cases, the cages were derivatized by the solvent (forming La@C₈₀-C₆H₃Cl₂ and La@C₈₂-C₆H₃Cl₂) and the following X-ray analysis disclosed rather unexpected cages: C₈₀(C _2v ;3) and C₈₂(C _3v ;7). In order to explain the challenging observations, a two-step computational treatment is presented. The first step deals with the high-temperature gas-phase formation of the underivatized endohedrals while the second step models the reaction with the solvent. The Gibbs free energies were evaluated for representative temperatures and the computational scheme was able to confirm high relative populations for the observed derivatized cages.