DFT studies of binding of fluoride anions with silyl-fluorescein derivatives

Fluoride is abundantly used in dental healthcare and pharmaceutical industry, it is harmful if it is found over certain concentration in drinking water and in soil. It is therefore essential to develop portable tools to detect fluoride. Fluorescence sensing can be used as a simple and sensitive tool to detect fluoride anions. Fluorescent detection of anions is less widely studied compared to metal cation and neutral organic small molecules. As such, the interactions between F- anion and two silyl-fluorescein based sensors were studied here using density functional theory (DFT). Chemical shifts and electronic properties of the free sensor and the sensors in the presence of different number of fluoride anions were obtained and compared. The DFT results show that strong binding responses can be found as a function of fluoride concentration. The change in UV-Vis spectra due to the presence of fluoride indicates they are promising sensor candidates for fluoride detection and further studies on fluorescence response of these sensors are worthwhile.