Enhanced Ring-Opening Efficiency of Fluorescence Photochromic Switches Based on Benzo[e]-Fused Dimethyldihydropyrene.

Abstract

Fluorophores have a significant impact on the photoswitching efficiency of photochromic systems such as azobenzene, dithienylethene, and spiropyrans by facilitating energy transfer processes that modulate the photoisomerization dynamics. In this study, we investigate the effect of side-chain functionalization of benzo[e]-fused dimethyldihydropyrene (BDHP) photochromic system with carefully selected fluorophores, namely anthracene and coumarin, on the ring-opening photoisomerization efficiency to the corresponding cyclophanediene (BCPD) form. The corresponding phenyl and naphthyl derivatives and the unsubstituted parent BDHP were studied as controls. Comprehensive photophysical analyses, including absorption and emission spectroscopy, along with quantum yield measurements, demonstrate efficient energy transfer from the attached fluorophores to the BDHP core, leading to an enhanced BDHP→BCPD isomerization process. This energy transfer mechanism significantly enhances the photoisomerization efficiency, resulting in more than a twofold increase in the ring-opening quantum yield compared to the nonfunctionalized BDHP controls. Additionally, the efficiency of photoisomerization of the coumarin-substituted derivative was extended in the switching studies in embedded solid polymeric matrices with efficient reversible photoisomerization, photostability over multiple switching cycles, and an all-optical logic gate. These findings demonstrate a promising strategy to improve the performance of the BDHP photochromic systems and their potential applications in molecular logic devices in thin film.