Regulating the excited state behaviors of 2-benzooxazol-2-yl-4,6-di-tert-butyl-phenol fluorophore by solvent polarity: A theoretical simulation

Abstract

• The enhanced hydrogen bonding provides the impetus to promote the ESIPT reaction. • Photo-induced increased electronic densities around N atom plays vital roles in attracting hydroxyl proton. • Non-polar solvents are more favorable for the ESIPT behavior of BDTBP compound. In view of the unique luminescent characteristics, ESIPT materials have attracted lots of eyes. Given promising highly efficient green-emitting material, 2-benzooxazol-2-yl-4,6-di- tert -butyl-phenol (BDTBP) reveals important properties in designing Schiff base optical sensors. In this work, solvent dependent excited state behavior and ESIPT process of BDTBP has been explored theoretically. Analyses of chemical structural variations and infrared (IR) vibrational spectra in both S 0 and S 1 state, the enhanced intramolecular hydrogen bonding interactions could be clearly found that promotes ESIPT tendency. Particularly, BDTBP in nonpolar solvents with stronger hydrogen bond reveals the easier PT tendency. Paying attention to the changes of HOMO and LUMO orbitals, it could be found the charge transfer happens in the excited-state molecules, the reorganization of charge densities should be conducive to promoting the ESIPT process. Simulated potential energy curves indicated the ultrafast ESIPT reaction occurs for BDTBP fluorophore, which could be regulated and controlled via solvent polarity.