Substituted xanthylocyanines, Part IV: Trinuclear dyes with a pyronine nucleus

Trinuclear, dicationic and cation–anionic dyes carrying a pyronine nucleus were synthesized. Whilst their absorption spectra displayed two bands corresponding to the absorption of the cyanine and pyronine chromophores, none of the dyes fluoresced, in contrast to the parent compounds. The spectral evidence suggests a significant, though not perpendicular, twist around the bond between the cyanine and pyronine moieties.