CONDENSED HETEROCYCLES WITH A THIAZOLE RING. 14 NATURE OF THE ELECTRONIC SPECTRA OF SYMMETRICAL POLYMETHINE DYES OF THE THIAZOLOTRIAZINE SERIES

Article abstract of DOI:10.1007/BF00475337

Symmetrical mono-, tri-, and pentamethinecyanine dyes with a thiazolo<3,4-b><1,2,4>triazine ring were synthesized.The electron-density distributions in the dye molecules in the ground and first and second excited states were obtained by quantum-chemical calculations.It was established that the first two electron transitions are localized on the same atoms and that charge transfer to the triazine fragment of the molecule is realized in the case of excitation.The degree of participation of the heterocyclic ring in the first electron transition, which is responsible for the color of the dye, decreases with lengthening of the polymethine chain.