Theoretical Design of Near-Infrared Fluorescent Sensor for F Anion Detection Based on 10-Hydroxybenzo[]quinoline Backbone.

Proper design and development of near-infrared (NIR) fluorescent sensors is very important for applications in vivo. In this work, we theoretically designed a ratiometric and NIR fluorescent sensor based on the 10-hydroxybenzo[]quinoline (HBQ) backbone via systematically investigating the substituent effects of electron-donating groups (-NH, -CH, -C(CH)) and electron-withdrawing groups (-NO, -CN, -F, -Cl, -CF) at the proton donor site on the proton transfer process in HBQ in both the S and the S states. According to the calculated potential energy profiles along the proton transfer as well as the photophysical properties among all the derivatives, we successfully screened out that 7NH-HBQ is a promising fluorescent sensor exhibiting the near IR emission spectra accompanied by the large Stokes shift. The potential use of 7NH-HBQ for F detection among anions (F, Cl, and Br) was further studied, and the results showed that 7NH-HBQ is very sensitive and selective toward F based on the intermolecular hydrogen bonding interaction between F and OH bond, forming a new complex FAC . The ratiometric change in the fluorescence intensity could be induced by the H-F bond transfer from the O atom to the N atom in the S state.