Theoretical insights into excited state behaviors of D3HF derivatives via altering atomic electronegativity of chalcogen

Inspired by the distinguished photochemical characteristics of new organic molecule containing the chalcogenide substitution that could be potentially applied across various disciplines, in this work, the effects of atomic electronegativity of chalcogen (O, S and Se) on hydrogen bond interactions and proton transfer (PT) reaction. We present the characteristic 2,8-diphenyl-3,7-dihydroxy-4H,6H-pyrano[3,2-g]-chromene-4,6-dione (D3HF), which is based on 3-hydroxyflavone (3HF) and contains intramolecular double hydrogen bonds that is the main objective of this study to explore in detail the influence of the change of atomic electronegativity on the dual hydrogen bond interaction and the excited state proton transfer (ESPT) behavior by photoexcitation. By comparing the structural changes and infrared (IR) vibrational spectra of the D3HF derivatives (D3HF-O, D3HF-S and D3HF-Se) fluorophores in S0 and S1 states, combined with the preliminary detection of hydrogen bond interaction by core-valence bifurcation (CVB) index, we can conclude that the hydrogen bond is strengthened in S1 state, which is favorable for the occurrence of ESPT reactions. The charge recombination behavior of hydrogen bond induced by photoexcitation also further illustrates this point. Via constructing potential energy surfaces (PESs) based on restrictive optimization, we finally clarify the excited state single PT mechanism for D3HF derivatives. Specially, we confirm change of atomic electronegativity has a regulatory effect on the ESIPT behavior of D3HF and its derivatives, that is, the lower the atomic electronegativity is more conducive to the ESIPT reaction.