Modulation of photochromic dynamics in donor-π-acceptor azobenzene derivatives: Impact of diphenylamine donor and π-bridge engineering

초록

This study presents a systematic investigation of novel donor-π-acceptor azobenzene derivatives (DPAC, DPAF, and DPAT) incorporating a sterically demanding diphenylamine (DPA) donor, varied π-bridges (benzene, furan, and thiophene), and a cyanoacrylic-acid acceptor. Through complementary application of density functional theory calculations and time-resolved UV–Vis absorption spectroscopy, we establish quantitative structure-property relationships governing photochromic behavior. The photoisomerization dynamics reveal characteristic biexponential E→Z conversion profiles, reflecting mechanistic pathway complexity towards photostationary states. Thermal Z→E relaxation processes demonstrate pronounced π-bridge dependence, with DPAC exhibiting substantially retarded kinetics compared to DPAF and DPAT, correlating precisely with computed activation barriers. Potential energy surface analyses reveal preferential adoption of inversion pathways in these push-pull systems, contrasting with the mechanistic bifurcation observed in unsubstituted azobenzene. The systematic variation in thermal stability and photoisomerization dynamics demonstrates the critical role of π-bridge electronic character in modulating excited-state behavior. These findings establish fundamental principles governing electronic and steric control of photochromic behavior, providing critical insights for rational design of advanced photoresponsive materials. © 2025

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