Pyrylocyanines. 11. Symmetrical tetraphenyl-substituted pyrylo-2-cyanines

Symmetrical polymethine dyes (monomethylidyne, carbo-, and dicarbocyanines), viz., 4,6-diphenylpyrylium, -thiopyrylium, and -pyridinium derivatives, were synthesized. It follows from a comparison of the absorption spectra of pyrylo-2-cyanines and their heteroanalogs with the spectra of the corresponding 4 isomers that these dyes differ from one another with respect to the positions, intensities, and forms of the bands. The pyrylocarbo- and -dicarbocyanines and their sulfur analogs are more deeply colored than their isomers, while the reverse regularity is observed in the pyridocyanine series. The long-wave bands in the spectra of all of the isomers are accompanied by more intensive transitions to the vibrational sublevels than in the case of the isomers.See 1] for Communication 10.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 898–902, July, 1980.