LAUSR

Abstract In this present work, we theoretically investigate the four HBO derivatives (i.e., HBO-NH2, HBO-OH, HBO-NO2, HBO-COOH) about their different excited state behaviors involved in excited state intramolecular proton transfer (ESIPT) process. Based on density functional theory (DFT) and time-dependent density functional theory (TDDFT) theoretical level, we analyze the bond lengths, bond angles and relative chemical changes about these four structures. In addition, coupling with the infrared (IR) vibrational spectra, we confirm that the intramolecular hydrogen bond O1 H2···N3 in these four structures should be strengthened in the S1 state, which might provide the possibility for ESIPT reaction. Further, studying the vertical excitation process, we explore the charge redistribution and find that more charge would be transferred from HOMO to LUMO orbital for electron withdrawing groups (i.e., HBO-NO2 and HBO-COOH). In other words, electron withdrawing groups NO2 and COOH would facilitate the ESIPT reaction. Via constructing the potential energy curves of both S0 and S1 states, we further confirm that electron withdrawing substitutions could promote the ESIPT process for HBO systems. We believe that this present work not only elaborates the different excited state behaviors of HBO-NH2, HBO-OH, HBO-NO2 and HBO-COOH, but also plays important roles in designing and developing new materials and applications in future.