Kenji Mochida

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 CHCl(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.

Efficient blue electroluminescence of silylene-bridged 2-(2-naphthyl)indole

We synthesised 12,12-diisopropyl-7-methyl-12H-indololo[3,2-d]-naphtho[1,2-b][1]silole from 1-bromo-2-naphtholvia four steps. The silylene-bridged 2-(2-naphthyl)indole exhibited intense blue photoluminescence in solution and in the solid state. For example, the fluorescence maximum of the powder appeared at 476 nm with a high quantum yield (Φ = 0.70). The organic light-emitting device using the silylene-bridged indole as a light-emitting layer demonstrated a high current efficiency of 3.80 cd A−1 and a power efficiency of 3.64 lm W−1 at 10 mA cm−2 with excellent colour coordinates (0.152, 0.094), while the device fabricated with the blue-emissive indole as a dopant achieved even higher current and power efficiencies of 6.68 cd A−1 and 5.58 lm W−1, respectively, at 10 mA cm−2.

Solid state structures and photophysical properties of (trimethylsilyl)methyl-substituted anthracenes and pyrenes.

(Trimethylsilyl)methyl groups incorporated at 9- and 9,10-positions of anthracenes and at 1,3,6,8-positions of pyrenes were found to orient perpendicular to the aromatic frameworks in their crystals and induce red-shift of UV absorption and fluorescence spectra and enhancement of fluorescence quantum yields as compared with the parent hydrocarbons.