Pyrylocyanines

Unsymmetrical selenaflavylocyanines containing flavylium, thiaflavylium, 1,3,3-trimethylindoleninium, or 1-ethylbenzothiazolium rings were synthesized. The deviations for the dyes obtained, which were calculated from the absorption maxima and by the band moment method, were compared with the same values obtained for similar dyes with flavylium or thiaflavylium rings in place of the selenaflavylium ring. The results indicate that the basicity of the heterorings in the polymethine dyes increases in the order selenaflavylium < thiaflavylium < flavylium. This is confirmed by a comparison of the deviations in hemicyanines and styryls.See [1] for communication II.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1177–1181, September, 1971.