Solvent polarity and chalcogen electronegativity synergistically regulate excited-state proton transfer in BBYPD derivatives.

This study aims to investigate the regulatory behaviors of solvent polarity and chalcogen electronegativity on excited-state proton transfer process of BBYPD derivatives, filling the theoretical gaps related to proton transfer pathways and regulatory rules of double hydrogen bond systems in similar studies. The study used DFT and TDDFT methods for systematic calculations, selected three solvents with different polarities (hexane, benzene, acetonitrile), and constructed two types of BBYPD derivative systems: symmetrically substituted (BBYPD-SS, BBYPD-SeSe) and asymmetrically substituted (BBYPD-OS, BBYPD-OSe). Results show hydrogen bonds of BBYPD derivatives are significantly enhanced in excited state, which is a key factor promoting proton transfer, the higher the solvent polarity, the more it can optimize the spatial configuration of hydrogen bonds and reduce reaction energy barriers, thereby facilitating proton transfer, the lower the electronegativity of chalcogen elements (i.e., O > S > Se), the stronger the intramolecular hydrogen bond interaction and the easier proton transfer occurs, and asymmetric derivatives only undergo proton transfer on the sulfur or selenium substituted side with low electronegativity. This study established a qualitative correlation between solvent polarity, atomic electronegativity, and the ESIPT behavior of BBYPD derivatives, providing theoretical support for the targeted development of functional materials such as optoelectronic devices and fluorescent probes.