Topochemically photoreacted fluorescent dimers of 2,3-dicyanopyrazines

Abstract

Novel fluorescent materials derived from 2,3-dicyanopyrazine were synthesized and subjected to photodimerization reaction. Styryl substituents were attached by Wittig reaction, and the [2+2] photocycloaddition of the 2,3-dicyanopyrazine, either in solution or as a thin film, was studied with irradiation under a high-pressure Hg lamp. The resulting compounds were characterized by H-1 NMR, FT-IR and elemental analysis. Spectral changes of UV-visible absorption intensity and fluorescent intensity were examined at specific exposure intervals. While the cyclobutane ring of dimers induced a discrete pi-conjugation with aryl substituents to show a hypsochromic shift of absorption and emission spectra, the fluorescence intensity was increased and the specific lowest unoccupied molecular orbital (LUMO) levels were formed compared to monomers. (C) 2011 Elsevier Ltd. All rights reserved.