Substituted xanthylocyanines. II. Pyroninocyanines

Symmetric and unsymmetric dyes derived from 9-methylpyronine have been obtained. Their absorption spectra exhibit an intensive long-wavelength band and a weaker short-wavelength one. The absorption maximum positions and the intensity ratio for the two bands are essentially influenced by the nature of the second end nucleus. The pyroninocyanines obtained are found to be stable long-wavelength dyes.