Unpaired-electron localization and delocalization in macromolecules with a system of conjugated C=C bonds

The radical polymerization of acetylene monomers has been studied in a wide temperature range (77–340 K) using EPR spectroscopy, calorimetry, chromatography, and gravimetry It has been found that the growing macroradical is active, and its unpaired electron is localized at a terminal fragment of the molecule. However, it lost its activity even at small chain lengths (less than ten monomer units) because of delocalization of the unpaired electron along the system of conjugated double bonds.     

Resonance in compounds with multiple conjugated bonds

The resonance of the compounds buta-1,3-diyne (1), buta-1,3-diene (2), hexa-1,3,5-triyne (3), hexa-1,3,5-triene (4), hexa-3-en-1,5-diyne (5), and hexa-1,5-dien-3-yne (6) was analyzed. The molecular geometry, π molecular orbitals, and the electron density of these compounds were analyzed. The NBO, AIM, and NRT methods were used. By comparing the electronic structures of compounds 1 and 2 and by considering that the latter is a classic example of a π-conjugated compound (Org Lett 5:2373–2375, 2003; Org Lett 5:2373–2375, 2004), it was possible to conclude that the conjugation of compound 1 is larger than that of 2. Compounds 3 and 4 were also studied, in order to understand the effect of a longer conjugated chain, and it was found that the resonance also increases in the case of 3. In addition, the effect of changing the order of the central bond was investigated by comparison of compounds 5 and 6 with 3 and 4, respectively. The results indicated that changes produce small alterations in the properties of compounds 3 and 4.     

Electronic structure of long molecules with conjugated bonds

The -electron system in a long molecule of the polyene type was calculated according to the Hartree-Fock self-consistent field method in which electrons with different spins are located on different molecular orbitals. The ground state of the -electron system in a long molecule is found to be antiferromagnetic and possesses a gap in the one-particle excitation spectrum. The calculated value of the first -electron transition as a function of the number of atoms in the polyene chain is in good agreement with experiment.     

Photophysical properties of polymers with a system of conjugated bonds and their use in light energy conversion processes

We consider the photophysical properties of polymers with a system of conjugated bonds and their use in light energy conversion processes. Based on our analysis of literature data we show that conjugated polymers of different classes (capable of exhibiting the properties of a dielectric, a semiconductor, or a metal) are characterized by efficient photoconductivity, photoluminescence, and electroluminescence. We determine the regularities in the dependence of the photophysical characteristics on the nature and structure of the conjugated polymers, their degree of doping, the energy and intensity of the incident light, the temperature, etc. In a series of polymers we show that conjugated polymers can be used in particular as photoconductors, electrophotographic materials, materials for lasers, electroluminescent diodes, and also solid-state photoconverters of light energy etc.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 30, No. 5, pp. 241–263, September–October, 1994.     

Molecular structure and photosensitivity of polyesters with conjugated double bonds

Photocrosslinkable polyesters of m- and p-phenylenebis(α-cyanoacrylic acids) ( I-a and I-b ), m- and p-phenylenebis(α-cyanobutadiene carboxylic acids) ( I-d and I-e ), p-phenylenebis(acrylic acid) ( I-c ), and p-phenylenebis(butadiene carboxylic acid) ( I-f ) were prepared, and their photosensitivities were investigated. The spectral sensitivities of I-a , I-c , I-d , and I-e ranged up to 365, 385, 510, and 560 nm, respectively. This order corresponds to that of λ_max due to the π-π^* transition in their absorption spectra. I-e was sensitive to the visible part of argon ion laser even in the absence of photosensitizer. The highest sensitivity observed with I-e was estimated to be 1.5 mJ/cm². In contrast, the sensitivity of I-c was low (> 10⁵ mJ/cm²) and that of I ′- d , a modified I-d , was 1300 mJ/cm², respectively. Addition of 2,6-di(4′-methoxyphenyl)-4-(4′-n-amyloxyphenyl)thiapyrylium perchlorate to them extended their sensitivity range, improving their sensitivity values to 35 and 110 mJ/cm², respectively.     

Some monomers,oligomers and polymers with conjugated triple bonds

In the first part new monoaminodiacetylenes with different numbers of CH₂-groups, the formation of Perowskit-type Mn complexes and their polymerizability are described. Symmetrical diaminodiacetylenes and some derivatives therefrom have also been prepared. The second part deals with different types of polymers with diacetylene units in the backbone. Under irradiation color formation and crosslinking take place. Well-defined low molecular weight model compounds of polydiacetylenes is the subject of the third part. Finally rod-like but soluble polymers with alternating p-phenylene and acetylene units are described.