Sensing of fluoride anion based on desilylation and intramolecular charge transfer of 2‐[2‐(tert‐butyl‐diphenyl‐silanyloxy)‐phenyl]‐4,5‐diphenyl‐1H‐imidazole

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AbstractIn view of the tremendous potential for fluorescent chemosensors, more and more people pay attention to design and synthesize high‐efficiency sensors. Given the importance of fluorescence response mechanism, in the present work, the specific sensing mechanism of a novel fluoride anion chemosensor 2‐[2‐(tert‐butyl‐diphenyl‐silanyloxy)‐phenyl]‐4,5‐diphenyl‐1H‐imidazole (abbreviated as TBDI) has been investigated based on density functional theory (DFT) and time‐dependent DFT (TDDFT) methods. Our theoretical electronic spectra (vertical excitation energies and fluorescence emission peaks) reproduced previous experimental results (Sensor Actuat B‐Chem. 2016, 232, 175), which confirms the rationality of our theoretical level adopted in this work. The constructed potential energy curve about fluoride‐triggered desilylation reaction suggests that the low barrier could be responsible for the rapid response to fluoride anion. Analyses about binding energies demonstrate that only fluoride anion could be detected for TBDI chemosensor in dimethyl sulfoxide (DMSO) solvent. In view of the vertical excitation process, the strong intramolecular charge transfer (ICT) process between the S0‐state and S1‐state transition explains the redshift of absorption peak for TBDI sensor with the addition of fluoride anion. This work not only presents a straightforward sensing mechanism of fluoride anion for TBDI sensor but also plays important roles in synthesizing and designing fluorescent chemosensors in future.