Theoretical insights into atomic-electronegativity-regulated ESIPT behavior for B-bph-fla-OH fluorophore

Abstract

Inspired by the potential applications for detecting cysteine and the novel phototriggered CO release molecule (photoCORM) property, B-bph-fla-OH is explored in this work about its excited state behaviors. In view of significance of atomic electronegativity in photochemical reactions, we mainly focus on decoding photo-induced hydrogen bonding interactions and atomic-electronegativity-dependent excited state intramolecular proton transfer (ESIPT) behavior for Bbph-O, Bbph-S and Bbph-Se derivatives. Combining optimized geometrical changes and infrared (IR) stretching vibration related to hydrogen bond Oa-Hb···Oc, the photo-induced hydrogen bonding strengthening can be confirmed. Via predicting bond energy (EHB), we find low atomic electronegativity is in favor of enhancing hydrogen bonding interactions in both S0 and S1 states. Charge reorganization stemming from photoexcitation and atomic-electronegativity energy gap between HOMO and LUMO orbitals further reveals the ESIPT tendency. Insights into potential energy surfaces (PESs) and constructing energy profiles via searching transition state (TS) for Bbph-O, Bbph-S and Bbph-Se, we present the atomic-electronegativity-regulated ESIPT mechanism and spectral behaviors. We sincerely wish the specific and controlled excited state dynamical behavior could pave the ways for designing and developing novel fluorescent sensors based on B-bph-fla-OH derivatives in future.