Development of Highly Fluorescent Materials Containing Pyrazine Ring

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Recently, fluorescent compounds are expected as the material for flat display, using electro-luminescence device, althogh some other applications have been realized. In the course of our reserch on liquid crystal and Langmuier-Blodgett film using pyrazine derivatives, we noticed that pyrazine derivatives show strong fluorescence. In this investigation, we synsthesize many pyrazine derivatives to develope highly fluorescnet material. Important results are as follow ;1. Three methds fot the synthesis of pyrazine derivatives were investigted. (1) Reaction of lithiated mechylpyrazine with carbonyl compounds followed by dehydration was revealed to give alkenyl pyrazine derivatives. (2) Azidomethylaryl ketones gave 2,5-diarylpyrazine by the reaction with triphenylphosphine. (3) Reactions of glyoxals or bromomethyl ketones with o-phenylenediamine gave quinoxalilne derivatives.2. In the case of 2,5-diarylpyrazines, electron-donating groups, such as p-methoxyphenyl or furyl group, ebhanced the fluorescence. Conjugative effects of large pi-electron system, such as naphthyl group, was also edffective for the enhancement of fluorescence. However, the furyl derivative in solution was not stable as to decompose in a few days.3. In the case of quinoxaline derivatives, substitution by methoxyphenyl, 2,3-dimetoxyphenyl, or N,N-dimethyphenyl group cenhanced fluorescence of the compound. Although, the fluorescence of these compounds were not strong as 2,5-diarylpyrazine, they were shown to be very stable.In this investigation, we could demonstrate that substitution by the group, having electron-donating effect and conjugative effect, enhances the fluorescence. On the basis of these results, we are now planning to prepare more stable pyrazine derivattives showing strong fluorescence.