Antoni Chyla

New theoretical insight into the thermal cis–trans isomerization of azo compounds: Protonation lowers the activation barrier

The detailed mechanism of thermal cis–trans inversion of protonated diazenes and azobenzenes has been investigated for the first time using ab initio Hartree–Fock (HF), density functional theory (DFT), second order Mo/ller–Plesset (MP2), and complete active space self consistent field (CASSCF) approaches. Protonation of one of the nitrogens at the N=N bond leads to a considerable (5–20 kcal/mol) reduction of the activation barrier. The magnitude of this effect depends on the electron withdrawing nature of the substituents and the differential stabilization of the transition state by positively charged functional groups. In the case of 4-phenylazopirydine protonated at pyridine nitrogen, the barrier is dramatically reduced to just 7 kcal/mol. This result establishes the lowest (close to an experimental estimate) ab initio value for the cis–trans isomerization for a substituted azobenzene. The structures of neutral and protonated transition states are similar, and the correlation effects for molecular param...

Two-component Langmuir and Langmuir-Blodgett films containing monomeric and polymeric alkylheteroaromates: surface plasmon resonance and electrical conductivity

Abstract Langmuir film formation was investigated in a series of alkylheteroaromatic compounds and their mixtures. In the case of pure amphiphilic molecules, the shape and nature of the hydrophilic group seems to play a decisive role in the film formation; however, in binary systems a positive synergy was observed allowing to obtain two-component film of reasonable quality even if one or both the components separately manifested moderate or weak ability for film formation. Compression and deposition of mixtures of poly(3- n -alkylthiophenes) with suitable builders is described. The thicknesses of the binary LB films, determined from the measurements of the surface plasmon resonance, are controlled by the packing of the film builder. The optical and electrical properties of the Langmuir-Blodgett films are modified by the presence of nitrogen oxides. The overall effect is probably due to two competing processes: doping of the polymer and an irreversible reaction destroying the conjugated chain.

Synthetic routes to bis(pyrrolyl)arylenes. Experimental and molecular modeling studies

The synthesis and characterization of compounds derived from 9,9-dialkylfluorene and 1,4-dioxane[3,4-b]thiophene are described. The key step involves a modified Steglich reaction between 9,9-dialkyl-2,7-N,N′-diallyliminochlorofluorene or 2,5-N,N′-diallyliminochloroethylenedioxythiophene and tert-BuOK (Route 1). Route 2 for bis(pyrrol-2-yl)dioxanethiophene, involving the reaction between 1,4-dioxane[2,3-c]thiophene and a dioxolanepropanol, is also a useful and general strategy. Molecular modeling studies indicate relationships between the molecular parameters (structure, ionization potential, atomic charges) of the synthesized moieties and their polymerization properties.

Gas Sensing Device Based on Phthalocyanine LB Films

Abstract An investigation of the electrical conductivity of films consisting of multilayers of tetra-t−butyl-substituted copper phthalocyanine (TTBCuPc) films exposed to various levels of nitrogen oxides in air (within the ppm range) was carried out. The TTBCuPc films were deposited, using the Langmuir-Blodgett (LB) technique, onto glass substrates. Gold interdigital electrodes (ca. 2μm thick, 100 μm wide and 100 μm spaced) were evaporated on the top of the films. High reproducibility and reasonable sensitivity of the sensors to the nitrogen oxide at a relatively low temperature (313 K) suggest that TTBCuPc may be a viable material for gas sensing devices.

CONVENIENT SYNTHESIS AND PHYSICOCHEMICAL PROFILE OF NEW DERIVATIVES OF PYRIMIDINE

A synthesis of linear oligoheterocycles based on the substituted pyrimidines are described. The desired compounds have been accomplished by the variation of the original Pinner synthesis in which the aliphatic nitrile reacted with hydrogen chloride to give imino ester. These compound reacted with ammonia gas to give amidine. Chalcones in reaction with amidines give bis(phenyl)pyrimidines. The bis(phenyl)pyrimidines reacted with 3,4- ethylenedioxy-2-trimethyltinthiophene or 2-trimethyltinthiophene in the presence of Pd(PPh3)2Cl2 or Pd(PPh3)4 as catalyst to give designed compounds. In this work are presented also some electrochemical measurements using Langmuir - Blodgett technique in mono- and binary systems.