Theoretical Investigation on Solvent Polarity and Atomic Electronegativity Effects on Stepwise <scp>ESDPT</scp> in <scp>BBYDPD</scp> Derivatives

ABSTRACT To reveal the excited‐state double proton transfer (ESDPT) mechanism within 2,7‐Bis‐benzooxazol‐2‐yl‐3,10c‐dihydro‐pyrene‐1,8‐diol (BBYDPD) derivatives, this study systematically explores the regulatory rules of solvent polarity (hexane, toluene, tetrahydrofuran, acetonitrile) and chalcogen element (O, S, Se) substitution on their ESDPT behaviors. Our results show that the intramolecular hydrogen bonds in S 1 state are significantly enhanced, and ESDPT proceeds via a stepwise route that exhibits a lower energy barrier relative to the concerted proton transfer route. Polar solvents strengthen hydrogen bonds and reduce energy barriers through the solvation effect; substitution with Se, a low electronegativity element, can further enhance excited‐state hydrogen bonds and electron delocalization, and the asymmetric structures of hetero‐substituted derivatives (BBYDPD‐OS/OSe) amplify such regulatory effects. This study clarifies the core regulatory mechanism of ESDPT in BBYDPD derivatives and offers theoretical support for the advancement of high‐performance functional materials, including organic light‐emitting diodes (OLEDs) and fluorescent sensors.