Syntheses and characterization of new styryl fluorescent dyes from DAMN .2.

2,3-Bis(bromomethyl)-5,6-dicyanopyrazine (3) can be prepared more readily by the condensation of DAMN (1) and 1,4-dibromobutane-2,3-dione (2) than by direct bromination of 2,3-dimethyl-5,6-dicyanopyrazine. The Wittig reaction of 3 with arylaldehydes gave a new type of fluorescent styryl dyes (6-8). These styryl dyes have extended pi-conjugation systems and strong intramolecular charge-transfer chromophoric systems. They have strong fluorescence in solution and some have fluorescence even in the solid state, which is very important to evaluate their electroluminescence (EL) property as the emitter for EL devices. Calculation of excitation energies using the PPP-MO method, and optimization of their structures using the MOPAC with the PM 3 method were conducted, and their spectral properties are discussed to correlate their functionalities with chemical structures. (C) 1997 Elsevier Science Ltd.