Enhancing fluorescence of benzimidazole derivative via solvent-regulated ESIPT and TICT process: A TDDFT study

In this work, we use density functional theory and time dependent density functional theory to explore the ESIPT and TICT process of 6-(1H-Benzoimidazol-2-yl)-2,3-dimethoxy-phenol (BIDOP) in cyclohexane (CHX) and tetrahydrofuran (THF) solvent, respectively. It reveals that ESIPT process of BIDOP can occur in both CHX and THF solvent at the first excited state with similar reaction barrier. Remarkably, compared to barrierless from keto (K*) to TICT state of BIDOP in THF solvent, the reaction barrier between K* and TICT state is up to 20.28 kcal/mol for in CHX that TICT process is inhibited in CHX solvent. The absence of nonradiative decay TICT state of BIDOP in CHX solvent induces higher fluorescence in CHX compared to in THF solvent. These findings indicate that CHX solvent can effectively enhance fluorescence of BIDOP. Our study highlights a convenient approach for enhancing fluorescence and is significant for photophysics and photobiology field.