Synthesis and photochromic modulation of aromaticity in dinaphthylethene derivatives

Abstract

Photoinduced modulation of aromaticity, intricately coupled with the reversible photoisomerization of diarylethenes, establishes a fundamental mechanism for tailoring photoreactivity and developing multifunctional optical materials. In this study, we present the synthesis and comprehensive photochemical characterization of dinaphthylethene derivatives 1o–4o functionalized with naphthalene side chains. Experimental results reveal that specific light irradiation enables precise modulation of both (i) the photochromic reactivity of 1o–4o and (ii) the aromaticity of their naphthalene substituents. To unravel the mechanistic link between photocyclization and aromaticity dynamics, we conducted nucleus-independent chemical shift (NICS) calculations and chemical bond character analyses of the naphthalene units. These theoretical insights, combined with experimental observations of photochromic reactivity, fluorescence intensity variations and rapid thermal back-reaction kinetics, establish a robust structure–function correlation: (i) light-driven cyclization selectively alters the electron delocalization in specific naphthalene rings; (ii) emission quenching correlates with closed isomer formation, enabling real-time monitoring of photostationary states; (iii) large activation energy barriers facilitate rapid thermal reversion, critical for reversible applications. Collectively, this work provides a strategic framework for designing photoresponsive diarylethenes capable of dynamically tuning both six-membered aromatic systems and optoelectronic properties. The synergistic integration of photoswitching, fluorescence modulation, and thermal stability positions these materials as promising candidates for next-generation photonic devices, including adaptive optoelectronics and erasable optical memory systems.