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

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[h]quinoline (HBQ) backbone via systematically investigating the substituent effects of electron-donating groups (-NH₂, -CH₃, -C(CH₃)₃) and electron-withdrawing groups (-NO₂, -CN, -F, -Cl, -CF₃) at the proton donor site on the proton transfer process in HBQ in both the S₀ and the S₁ 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 7NH₂-HBQ is a promising fluorescent sensor exhibiting the near IR emission spectra accompanied by the large Stokes shift. The potential use of 7NH₂-HBQ for F^- detection among anions (F^-, Cl^-, and Br^-) was further studied, and the results showed that 7NH₂-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_S . 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 S₁ state.