SYNTHESIS AND PROPERTIES OF NEW STYRYL DYES DERIVED FROM 2,3-DICYANO-5-METHYLPYRAZINES

Reaction of 2,3-dicyano-5-methylpyrazine derivatives (3a-e) with aryla ldehydes gave new florescent styryl dyes (4-8). These styryl dyes have extended pi-conjugated systems and are strong intramolecular charge-t ransfer chromophoric systems. They are of interest as non-linear optic al materials, which should produce a large dipole moment in the excite d state, and consequently induce large dipole moment differences accom panying laser irradiation. The styryl dyes derived from 2,3-dicyano-6- hydroxy-5-methylpyrazine showed large solvatochromism, depending on th e polarity of the solvent, due to tautomerism between the hydroxypyraz ine and the pyridone forms. The fluorescence and solvatochromism prope rties of dyes 4-8 were also studied, and structure-property relationsh ips in solution an din the solid state were evaluated on the basis of molecular stacking in the solid state. (C) 1996 Elsevier Science Ltd