Fluoride anion sensing mechanism of a BODIPY-linked hydrogen-bonding probe

The sensing mechanism of a fluoride-anion probe BODIPY-amidothiourea (1c) has been elucidated through the density functional theory (DFT) and time-dependent density functional theory (TDDFT) calculations. The theoretical study indicates that in the DMSO/water mixtures the fluorescent sensing has been regulated by the fluoride complex that formed between the probe 1c/two water molecules and the fluoride anion, and the excited-state intermolecular hydrogen bond (H-B) plays an important role in the fluoride sensing mechanism. In the first excited state, the H-Bs of the fluoride complex 1cFH(2) are overall strengthened, which induces the weak fluorescence emission. In addition, molecular orbital analysis demonstrates that 1cFH(2) has more obvious intramolecular charge transfer (ICT) character in the S-1 state than 1cH(2) formed between the probe 1c and two water molecules, which also gives reason to the weaker fluorescence intensity of 1cFH(2). Further, our calculated UV-vis absorbance and fluorescence spectra are in accordance with the experimental measurements. (c) 2018 Wiley Periodicals, Inc.