Synthesis and photophysical properties of 1,4-bis(4,5-diarylimidazol) benzene dyes

A class of π-conjugated 1,4-bis(4,5-diarylimidazol)benzene dyes (1–5) are synthesized, and all dyes exhibit strong fluorescence in solution (ϕf = 0.96–0.45, in DMSO). It is found that both absorption and fluorescence of dyes are influenced by molecular structures and electronic properties of substitute groups, but little influenced by the polarity of solvents and pH value. Besides, two-photon properties of dyes are also investigated. The largest two-photon absorption cross-section (σ = 98 GM) for dye 4 is obtained with 700 nm in DMSO, and two-photon fluorescence emission is also observed with 740 nm excitation in solution.