Elaborating and modulating the excited state intramolecular proton transfer behavior for 2-benzothiazole-2-yl-5-hex-1-ynyl-phenol

Abstract

Excited state intramolecular proton transfer (ESIPT) of organic molecules has been drawing continuously considerable interests. This reaction 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-benzothiazole-2-yl-5-hex-1-ynyl-phenol (BYHYP) molecule. Based on DFT and TDDFT means, we firstly examine and certify hydrogen bond O–H···N role in BYHYP. Probing into molecular structure, infrared (IR) vibrational behaviors and computational hydrogen bonding energies, we validate O–H···N of BYHYP is enhanced in S1-state via photoinduced excitation. Accessorial negative electronic densities over N atom facilitate attracting hydrogen proton, which caters to the truth of strengthening hydrogen bond in S1. In addition, frontier orbital gap indicates that the solvent polarity plays vital roles in affecting excited state courses for BYHYP system. By means of potential energy curves (PECs) in four kinds of solvents, we propose the ultrafast ESIPT mechanism for BYHYP by explaining previous experimental characteristics. Along the way of ESIPT, we search the transition state (TS) and present the regulation mechanism for BYHYP via solvent effects.