Self-assembling of aminopyrazine fluorescent dyes and their solid state spectra, Part 2

2,5-Diamino-3,6-dicarboxy pyrazine derivatives have a strong intramolecular charge-transfer chromophoric system and are new fluorescent candidates for many applications. The thioester and carbamoyl derivatives were newly synthesized and their solid state spectra were evaluated with respect to their molecular stacking. Hydrophobic interactions of the n-butyl groups were observed but intermolecular pi¯pi interactions were not observed from the X-ray crystal analysis of 2,5-diamino-3,6-bis(butoxycarbonyl)pyrazine. These space-filling intermolecular interactions of dicyanopyrazines make it possible to construct strong three dimensional molecular stacking in single crystals, which affect their solid state absorption spectra.