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