3,6-Diazaxanthylium Salts: Dyes with a New Chromophore

A new tricyclic framework is the characteristic feature of the violet, air‐sensitive dyes 1. The phenyl substituent X (X = Ph, 4‐CF3‐C6H4) is arranged orthogonally to the chromophore both in the crystal and in solution, and the tricycle is bent by about 5° about the axis C9–O10. In comparison to the frequently used rhodamines, compounds 1 absorb at longer wavelengths and fluoresce with lower quantum yields.