Pyrylocyanines. 20. Symmetrical methoxy-substituted tetraphenyl-pyrylocyanines and their heteroanalogs

Symmetrical tetraphenyl-substituted -pyrylo-, -thiopyrylo-, and -pyridotrimethylcyanines, containing electron donor methoxy groups in two or four phenyl rings, were synthesized. Using the methods of quantum chemistry, the characteristics of the long-wave absorption bands of the dyes obtained are discussed. The independence of the theoretical conclusions from the selection of the quantum chemical parameters was demonstrated. The hypothesis of greater participation of the carbon-carbon bonds of the oxygen- and especially the sulfur-containing heteroresidues in comparison with the nitrogen-containing residues in the general system of conjugation is confirmed.For communication 19, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1486–1491, November, 1984.