Synthesis, Crystal Structure, and Photophysical Properties of (1E,3E,5E)-1,3,4,6-Tetraarylhexa-1,3,5-trienes: A New Class of Fluorophores Exhibiting Aggregation-Induced Emission

Double Horner-Wadsworth-Emmons reaction of (E)-2,3-diaryl-1,4-bis(diethylphosphonyl)but-2-ene with (p-substituted) benzaldehydes gave (1E,3E,5E)-1,3,4,6-tetraarylhexa-1,3,5-trienes in moderate to good yields. Substitution of electron-withdrawing or -donating groups at the para position of the 1,6-diphenyl groups induced a slight bathochromic shift of UV spectra measured in CHCl(3) compared with that of the parent 1,3,4,6-tetraphenylhexa-1,3,5-triene. Although fluorescence was not observed with all the trienes in CHC(3), they markedly emitted visible light in powder forms with quantum yields of 0.15-0.44. Introduction of amino groups at the para position of the 3,4-diphenyl groups induced a bathochromic shift of emission maxima with good solid-state quantum yields. Thus, the tetraarylated triene framework is found to serve as a new class of fluorophores that exhibit aggregation-induced emission.