Solvatochromism of Heteroaromatic Compounds: XVI. Theoretical Study of the Effect of Nonspecific Solvation on the Rotational Isomerism and Spectral Characteristics of 2-[2,2-Dicyano-1-(methylthio)vinyl]-5-methylpyrrole

The effect of nonspecific solvation of the relative stability of rotational isomers of 2-[2,2-dicyano-1-(methylthio)vinyl]-5-methylpyrrole was studied theoretically (HF/6-31G*) in terms of the Onsager model. In the free form this compound exists as an ensemble of four nonplanar C, N, S rotamers, the largest energy gap between which being no more than 2 kcal/mol. The effects of media whose generalized parameters correspond to chloroform and 1,2-dichlroethane reduce this gap to 0.7 and 0.5 kcal/mol. The vibration spectra of the rotamers and characteristics of the π→π* electronic transitions with intramolecular charge redistribution were calculated. Prospects of experimental studies of the solvatochromism and conformational isomerism of the title compound were discussed.