Theoretical unraveling detailed excited state proton transfer mechanism for 2,5‐bis (benzoxazol‐2‐yl)thiophene‐3,4‐diol‐ethyl compound in different solvents

Abstract

AbstractExcited state intramolecular proton transfer (ESIPT) of organic molecules has been drawing continuously considerable interests. It is not only one of the most basic processes in life but also exists in wide of application fields. In this work, we theoretically make a thorough inquiry about molecular excited state trends and ESIPT procedures for the novel highly miscible 2,5‐bis (benzoxazol‐2‐yl)thiophene‐3,4‐diol‐ethyl (BBTE) molecule. Based on DFT and TDDFT means, we first examine and certify hydrogen bond O1–H2···N3 role in BBTE. Probing into molecular structure and infrared (IR) vibrational behaviors, we validate O1–H2···N3 of BBTE is enhanced in S1 state via photo‐induced excitation. Accessorial negative electronic densities over N3 atom facilitate attracting hydrogen proton, which caters to the truth of strengthening hydrogen bond in S1. In addition, frontier orbital gap indicates the solvent polarity plays vital roles in affecting excited state courses for BBTE. By means of potential energy curves (PECs) in three kinds of solvents, we propose the ultrafast ESIPT mechanism for BBTE with explaining previous experimental characteristics. Along the way of ESIPT, we present the regulation mechanism for BBTE via solvent polarities.The enhanced hydrogen bond and charge redistribution facilitate excited state intramolecular proton transfer (ESIPT) reaction for 2,5‐bis (benzoxazol‐2‐yl)thiophene‐3,4‐diol‐ethyl (BBTE) system. Frontier orbital gap reveals that solvent polarity could play vital roles in controlling excited state dynamical behaviors for BBTE compound. Solvent polarity could regulate and control the ultrafast ESIPT behavior for BBTE molecule.