Electronic properties of polymethine systems. 12. Solitonic nature of charge distribution in the excited state

The electron density distribution in the excited state as compared with the ground state of the ionic polymethine dyes containing both the simplest terminal groups and carbo- and heterocyclic residues are considered. It is found that the charge waves in the excited state are of solitonic nature, however, excitation causes the considerable change in their shape. The dimension of the soliton becomes significantly shorter in excited state than in the ground state; the wave shape and width are highly sensitive to donor strength of terminal groups. In the asymmetrical form, the solitonic wave is shifted to the polymethine chain center.