Exploring ESInterPT behaviors of water sensitive probes: 3HF derivative clusters

•The excited-state intermolecular proton transfer in 3HF-D-(H2O)1-3 follows concerted mechanism.•The differences in excited-state thermodynamic and kinetics of 3HF-D-(H2O)1-3 clusters results in different sensitivity of 3HF derivative to water.•The water sensitivity is correlated with the excited-state charge transfer degree. The fluorescent probe molecules 3-hydroxyflavone derivatives (PPC, EPC and MNC) have been synthesized and for the first time realized the dual color fluorescence imaging of lipid droplets (J. Am. Chem. Soc., 2021, 143, 3169–3179), and PPC and EPC demonstrate the fluorescent sensitivity to water. In this work, the excited-state intermolecular proton transfer (ESInterPT) process in the clusters of 3HF-D with water molecules ((3HF-D-(H2O)n, abbreviated as D-(H2O)n: n = 1, 2, 3, 1 + 2, 2 + 1; D = PPC, EPC, MNC) are investigated by means of the time-dependent density functional theory (TDDFT) method. Based on the calculated potential energy scheme, we found that the dynamics and thermodynamic of excited-state intermolecular proton transfer in D-(H2O)n are different and dependent on the number of water molecules, but all proton transfer processes follow the concerted mechanism. We further reveal the water sensitivity of PPC, EPC and MNC, and theoretically confirm the feasibility of PPC and EPC as water sensitive probes. Besides we found the water sensitivity is correlated with charge transfer degree. This work provides significant insight into fluorescent sensing water using 3HF derivatives which is useful for rational design of new organic fluorescent probes with excellent performance.