A theoretical investigation about sensing mechanism of fluoride anion for (E)-2-(2-(dimethylamino)ethyl)-6-(4-hydroxystyryl)-1H-benzo[de]-isoquinoline-1,3 (2H)-dione

In the present work, we theoretical study the sensing mechanism of a new fluoride chemosensor (E)-2-(2-(dimethylamino)ethyl)-6-(4-hydroxystyryl)-1H-benzo[de]-isoquinoline-1,3(2H)-dione (the abbreviation is NIM). Based on density functional theory and time-dependent density functional theory methods, the fluoride anion response mechanism has been confirmed via constructing potential energy curve. The exothermal deprotonation process along with the intermolecular hydrogen bond O-HF reveals the uniqueness of detecting F-. After capturing hydrogen proton forming NIM-A anion configuration, a new absorption peak around 655nm appears in dimethyl sulfoxide solvent. In addition, the emission of NIM can be quenched when adding F- has been also confirmed. Due to the twisted intramolecular charge transfer character NIM-A-S-1 form, we further verify the experimental phenomenon. The theoretical electronic spectra (vertical excitation energies and fluorescence peak) reproduced previous experimental results (ACS Appl. Mater. Interfaces 2014, 6, 7996), which not only reveals the rationality of our theoretical level used in this work but also confirms the correctness of geometrical attribution. In view of the excitation process, the strong intramolecular charge transfer process of S0S1 transition explain the redshift of absorption peak for NIM with the addition of fluoride anion. This work presents a straightforward sensing mechanism (deprotonation process) of fluoride anion for the novel NIM chemosensor.