Crystallization-induced emission of 1,2-bis(3-methyl-5-(4-alkylphenyl)-2-thienyl)perfluorocyclopentenes: A mechanical and thermal recording system

Abstract

Organic luminescent materials have attracted much attention due to potential application to organic optoelectronics. Search for new molecules with high fluorescence quantum yield in solid states is one of the most important tasks in the research field of the organic luminescent materials. Here, we newly synthesized diarylethenes, 1,2-bis(3-methyl-5-(4-alkylphenyl)-2-thienyl)perfluorocyclopentenes having methyl, ethyl, n-propyl, and n-butyl substituents at the p-position of phenyl rings, and investigated their fluorescence properties in the solid states. The diarylethenes in the crystalline phase exhibited strong fluorescence with relatively high fluorescence quantum yields (Φf) of 0.12–0.20 compared with those in the amorphous phase (Φf = 0.064–0.069), which indicates that the diarylethenes have crystallization-induced emission (CIE) characteristics. The diarylethene having methyl group as the alkyl chain has the highest Φf value among the diarylethenes that we synthesized in this work. We found that the amorphous solid of the diarylethene having methyl group was crystallized after mechanical scratching followed by heating at 90 °C. We successfully demonstrated reversible fluorescence recording based on CIE characteristics and mechanical scratching and heating induced crystallization.