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.     

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.     

Synthesis of (2′-Methyloxiranyl)quinones as bioreductive alkylating agents

1,4-Benzoquinones and 1,4-naphthoquinones bearing 2′-methyloxiranyl substituents have been synthesized as new bioreductive alkylating agents. The method presented here involved the synthesis of 2-acetyl-1,4-dimethoxybenzenes 6a, b, d and -naphthalenes 6c, e, f , conversion of the acetyl group into 2′-methyloxirane ring using trimethylsulfonium chloride and sodium hydroxide in anhydrous medium, and oxidative demethylation of these intermediates 7a-f to quinones 8a, c, e, f with silver(II) dipicolinate.     

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.     

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.