Larissa Alexandrova

Cryochemical synthesis of Mg-containing poly(p-xylylene)

The organomagnesium compounds included in the polymer chain were produced by solid-state photopolymerization of p-xylylene at 80 K. The structure of the compounds and features of the obtained polymer are discussed using the infra-red and Raman spectroscopic data.

Manganese (I) complexes of p-xylene and [2n] cyclophanes from a theoretical sight

Abstract Theoretical B3LYP/6-311G** calculations were performed in order to understand the electronic structure and the structural behavior of bis( p -xylene) and bis([2,2]- p -cyclophane) manganese (I) complexes. The minimum energy configuration of bis( p -xylene) has D 2 d symmetry while that of bis([2,2]- p -cyclophane) has D 2 symmetry. The energy difference between the D 2 d and the D 2 h structures for both compounds is small. The results of the calculation for the pseudorotational barrier indicate that a process of interconversion may be possible. A comparison between experimental and theoretical infrared spectra was done for bis( p -xylene) Mn(I). Theoretical and experimental spectra are in good agreement. For both compounds, the HOMO has a big contribution from the metal orbital. In bis([2,2]- p -cyclophane) manganese (I) the HOMO and HOMO-1 form a bridge between the rings, this can explain some of the electric flow. Much of the evidences that we present in this work, indicates that transannular electronic interaction for bis([2,2]- p -cyclophane) manganese (I) is present.

Topochemical polymerization of butadiynylene dibenzamides

SummarySeries of meta- and para-substituted butadiynylene dibenzamides were synthesized, and their solid state polymerization was studied. The meta-isomers were light sensitive but not heat sensitive. The polymerizability of para-isomers depended on the type of N-substitutents. The polydiacetylenes from the para-isomers were blue, while those of the meta-isomers were light purple. Studies with molecular models and computer imaging suggested that hydrogen bonding between the topochemically polymerizable dibenzamides in the polymerization array is rather unlikely.

Bulk polymerization of 1,3,5,7-tetravinyltetramethylcyclotetrasiloxane induced by gamma radiation

Abstract Gamma ray-induced bulk polymerization of 1,3,5,7-tetravinyltetramethylcyclotetrasiloxane at ambient temperature has been investigated. It was found that the polymerization proceeds via a free radical mechanism through the reaction of vinyl groups, and the resulting polymer had a three-dimensional network structure. Kinetic features of the reaction were also studied, strong postpolymerization effects were observed at doses between 8 and 80 kGy. The composition of the sol fractions was determined by high pressure liquid chromatography, and the chemical structure of both the sol and gel fractions was analyzed by FTIR spectroscopy. Thermal stability of the gel fractions, determined by thermogravimetric analysis, and the thermomechanical behavior of unextracted samples were found to depend on the irradiation dose.

Theoretical simulation of the topochemical polymerization of some diacetylene molecules

The solid-state reaction of crystalline diacetylenes to yield polydiacetylenes is studied from a theoretical point of view to understand the possible reaction pathway and the nature of the resultant crystal in the case of a meta-substituted isomer. The lack of crystallization of the para isomer of the same molecule is also analysed, and it is shown that the large change required of the crystal cell parameters can explain this feature.

Synthesis and characterisation of fully aromatic lactamimide-containing polyesters

Three novel aromatic naphthalene-lactamimide monomers were synthesised and polymerised via high temperature transesterification in melt to produce fully aromatic lactamimide-containing polyesters. Molecular modelling of the synthesised polymers showed that they should possess better solubility compared to the respective polyimides due to the more flexible polymer chain. Some of the synthesised polymers are soluble in chloroform and show medium molecular weight. Polymers were found to be rather thermostable exhibiting T 10 up to 510°C. Aromatic polylactamimides did not show strong photoemission, probably due to Loose-Bolt quenching, however, the third order non-linear optical susceptibilities of the polymers were up to 9. 1 × 10 -11 esu, which is 5 times that of polylactamimides bearing aliphatic substituents and comparable with those of polydiacetylenes, polyanilines and polythiophenes known for their non-linear optical properties.

Low-Temperature Route to 1, 2-Benzoylenebenzimidazole Ladder Structure

Low-temperature catalytic conversion of N-(o-aminophenyl)phthalamic acid (I) was studied as a model reaction for the synthesis of ladder poly(aroylenebenzimidazole)s. The treatment of I with acetic anhydride/pyridine or trifluoroacetic anhydride resulted in the selective and quantitative cyclodehydration to yield either imide or isoimide structures respectively. The imidization was accompanied by acylation of the ortho amino group to form lateral acetamide or trifluoroacetamide substitutes. Thermodynamically unstable N-(o-trifluoroacetamidophenyl)phthalisoimide (III) underwent secondary cyclization to yield ladder 1, 2-benzoylenebenzimidazole (V) between 130 and 150 °C. The conversion of this reaction did not exceed 35% because it competed with the thermal isomerization of III to the stable N-(o-trifluoroacetamido-phenyl)phthalimide (IV). The cyclization of N-(o-trifluoroacetamidophenyl)phthalisoimide (III) was found to be possible even at room temperature. The formation of 30–35% of the ladder 1, 2-benzoylene-benzimidazole (V) was observed after III was dissolved in DMF and stored at room temperature for 4–10 h. This also was accompanied by the catalytic isoimide-to-imide isomerization. The obtained data may be useful for the further development of novel low-temperature approaches to the synthesis of ladder poly(aroylenebenzimidazole)s. Synthesis of aromatic polyimides and polyisoimides with lateral alkylamide or trifluoroalkylamide from available aromatic dianhydrides and tetraamines may also be of practical interest.

Pathway for polymerization of p-xylylenes

Abstract The pathway for polymerization of p -xylylenes is analysed at a theoretical level. The influence of the substituents on the aromatic ring on the conditions of the reaction is discussed on the basis of the Taft and Topson rules and Δ q π constants.

Hybridization vs. bond stretching isomerism in Ru(II) cyclometalated complexes of 2-phenylpyridine.

The phenomenon of formation of two isomers, yellow and orange, of the cyclometalated Ru(II) complex, [Ru(o-C6H4-py)(MeCN)4]+, was investigated by EELS spectroscopy and theoretical calculations. Both forms show very similar structures and spectroscopic properties, but slight differences in X-ray data and absorption between them were noted. No double minimum on the potential energy surface was found and thus these two forms cannot be considered as bond stretching isomers. However, the DFT study revealed the change in the hybridization of the carbon in trans-position of one of acetonitrile ligands. This effect can be responsible for the difference in colour. The results of the theoretical modelling coincide well with the experimental EELS data.

Theoretical study of N-(o-aminophenyl amic) acid cyclodehydration to 1,2-benzoilenebenzimidazole as a model reaction of ladder polypyrrones synthesis: thermodynamic and thermochemical data

Abstract The mechanism of polyimidazopyrrolones formation was studied via thermodynamic simulation of N-(o-aminophenyl)amic acid cyclodehydration to 1,2-benzoylenebezimidazole. It was found that 2-(o-carboxyphenyl)benzimidazole and N-(o-aminophenyl)phthalimide were the most thermodynamically favorable intermediates of this process. The thermodynamic possibility of 1,2-benzoylenebezimidazole formation from N-(o-acetamidophenyl)phthalimide and N-(o-trifluoroacetamidophenyl)isophthalimide was also evaluated using the same method. All thermodynamic values were obtained from semiempirical quantum mechanics calculations.