DFT study of the stabilization preconditions of the indoline spiropyrans with a cationic substituent

The computational modeling results are presented in the defining points of the isomerization process of the spiropyrans with cationic vinyl-3H-indolium substituent in the positions 6' and 8' of the 2H-chromene moiety taking into account DMSO solvent. The role of effective conjugation is revealed, that determines the significant difference in the behavior of the studied systems, based on the data of NBO energetic analysis and the atomic charge transfer analysis. The model shows that the interaction between an anion and a cation in these compounds has predominantly electrostatic nature without chemical bonds in the NBO terms.