Dipyrrolonaphthyridinediones--structurally unique cross-conjugated dyes.

Red-emissive dyes based on a previously unknown skeleton--dipyrrolo[1,2-b:1',2'-g][2,6]naphthyridine-5,11-dione--can be easily synthesized from simple and inexpensive reagents by one- or two-step routes. A careful selection of the substituents gives access to a variety of dipyrrolonaphthyridinedione derivatives with intense fluorescence in the range of 520-740 nm.