The sensing mechanism of fluoride anion for a novel molecule D2: Desilylation and intramolecular charge transfer

Abstract

In this work, the sensing mechanism of a new fluoride chemosensor 12‐([tert‐butyldiphenylsilyl]oxy)‐8a,13a‐dihydro‐7H‐benzo[de]benzo[4,5]imidazo[2,1‐a]‐isoquinolin‐7‐one (abbreviated as D2) is investigated using density functional theory (DFT) and time‐dependent DFT (TDDFT) methods. The theoretical electronic spectra (vertical excitation energies and fluorescence peak) reproduced previous experimental results (D. Li et al., Spectrochim. Acta A Mol. Biomol. Spectrosc. 2017, 185, 173), which confirms the rationality of the theoretical level used in this work. The constructed potential energy curve of the desilylation process suggests that the low barrier could be responsible for the rapid response to fluoride anions. Analyses of the binding energies show that only fluoride anion can be detected by D2 chemosensor in dimethylsulfoxide (DMSO). In view of the excitation process, the strong intramolecular charge transfer (ICT) process of the S0 → S1 transition explains the red shift of the absorption peak of the D2 sensor with the addition of fluoride anions. This work not only presents a straightforward sensing mechanism of sensing of the fluoride anion by the D2 chemosensor but should also play an important role in the synthesis and design of fluorescent sensors in future.