How an Eight-Membered Ring Alters the Rhodamine Chromophore.

Readily available phenylene-1,3-diamines can be converted into unprecedented analogs of rhodamine and malachite green pos-sessing a central eight-membered ring in three steps. The overall process couples a cyanine chromophore with a urea bridge giv-ing rise to new dyes possessing distinct spectral characteristics: absorption of orange light combined with weak emission of red light both in solution and in the crystalline state. Their photophysics is governed by the twist of lateral phenyl rings and intra- and intermolecular CT transitions.