Effects of Chalcogen Atoms on Excited-State Double-Proton Transfer Behavior for 3,6-bis(4,5-Dihydroxyoxazo-2-yl)benzene-1,2-diol Derivatives: A Computational Investigation

The impact of the chalcogen atomic electronegativity (O, S, and Se atoms) of new organic molecules on excited-state dynamical reactions is self-evident. Inspired by this kind of distinguished photochemical characteristic, in this work, we performed a computational investigation of chalcogen-substituted 3,6-bis(4,5-dihydroxyoxazo-2-yl)benzene-1,2-diol (BDYBD) derivatives (i.e., BDYBD-O, BDYBD-S, and BDYBD-Se). In this paper, we pay close attention to characteristic BDYBD derivatives that contain intramolecular double hydrogen bonds (O1-H2 center dot center dot center dot N3 and O4-H5 center dot center dot center dot N6). The main goal of this study was to explore how changes in atomic electronegativity affect the way hydrogen bonds interact and how excited molecules affect transfer protons. We go into further detail in the main text of the paper. By fixing our attention to geometrical variations and infrared (IR) vibrational spectra between the S0 and S1 states, exploring hydrogen bonding behaviors using the core-valence bifurcation (CVB) index, and simulating hydrogen bonding energy (EHB) via the atom in molecule (AIM) method, we clarified the photo-induced strengthened dual hydrogen bonding interactions that facilitate the excited-state dual-proton transfer (ESDPT) behavior of BDYBD derivatives. The reorganization of charge stemming from photoexcitation further verifies the tendencies of ESDPT reactions. We relied on constructing potential energy surfaces (PESs) by adopting a restrictive optimization approach, and herein, we finally clarify the gradual ESDPT mechanism of BDYBD derivatives. Particularly, we confirm that the variation in chalcogen atomic electronegativity has a regulatory effect on the ESDPT behavior of BDYBD derivatives; that is, the lower the atomic electronegativity, the more favorable it is for the gradual ESDPT reaction.