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Teoret. i eksperim. khimiya. 2004. Vol.40 No. 2. p. 83-87

Length of Soliton Wave in Excited State in Cationic Symmetrical Pyridocyanines
and Their Carbo- and Heteroanalogues


A. D. Kachkovsky, M. Yu. Kornilov*, D. N. Shut

Institute of Organic Chemistry, National Academy of Sciences of Ukraine
5 Murmanska Vul., 02094 Kyiv, Ukraine

* Taras Shevchenko Kyiv National University
64 Volodymyrska Vul., 01033 Kyiv, Ukraine

The quantum-chemical calculations of the optimized geometry in the ground state as well as the distribu- tion of electron density in FrankñCondon exited state of the polymethine dyes [R+-(CH=CH)n-H=R], where R are phenyl substituents or pyridinium, pyrylium and thiapyrylium residues, and n = 1-6, were performed in AM1 approximation. It was found that excitation of the molecule leads to decreasing the length of the charge wave (soliton). The length of the soliton was shown to depend on electrondonor ability of the endgroups R and on the length of the conjugated chain. In the thiapyrylocyanines, a decrease of the soliton size is accompanied by breaking of its symmetry.

Key words polymethine dyes, excited state, quantum-chemical calculations, soliton.