SYNTHESIS OF PROTON-TRANSFER FLUORESCENT DYES - 2,5-BIS(2'-BENZAZOLYL)HYDROQUINONES AND RELATED-COMPOUNDS

The synthesis and efficient purification of the fluorescent dyes 2,5-bis(2'-benzimidazolyl) hydroquinone (1) and 2,5-bis(2-benzoxazolyl)hydroquinone (2), in the quantities needed for laser work, are reported Additionally, simple modifications of these procedures are described for obtaining the corresponding monoheterocyclic compounds 4-(2'-benzimidazolyl)- and 4-(2'-benzoxazolyl)-2,5-dihydroxybenzoic acids 3 and 4. Methylation and/or acetylation of bisbenzoxazole 2 yielded the respective mono- and disubstituted derivatives, which are important model molecules for the photophysical study of the parent dye.