High-Contrast On/Off Fluorescence Switching via Reversible <i>E</i>–<i>Z</i> Isomerization of Diphenylstilbene Containing the α-Cyanostilbenic Moiety

Abstract

Fluorescence switching or modulation of π-conjugated molecules is of great interest in the area of optoelectronic materials science and technology because of their promising applications. However, the "concentration fluorescence quenching" problems commonly associated with conventional π-conjugated molecules in the solid state were occasionally an obstacle to use of π-conjugated molecules in high-contrast memory storage devices. We designed and synthesized a novel class of fluorescence switching π-conjugated molecule, (Z)-CN-MBE, that exhibits a reversible photo/thermal E/Z isomerization process, accompanied by a remarkable fluorescence on/off switching in the solid state. This may provide a promising way to construct high-contrast optical binary memory storage devices. (Z)-CN-MBE is virtually nonfluorescent but exhibits an extraordinary Z to E isomerization upon external light/thermal stimuli even in the solid state with a concomitant drastic fluorescence enhancement owing to the unique "aggregation-induced enhanced emission" (AIEE)' phenomenon of its trans isomer.