Synthesis, Crystal Structure and Optical Properties of 3,5-Dihydroxyphenyl-5-(dimethylamino)naphthalene-1-sulfonate as a Fluorescence Sensor for Fluoride Ion Detection

3,5-Dihydroxyphenyl-5-(dimethylamino)naphthalene-1-sulfonate, also referred to as sensor R1, was synthesized and characterized by 1H- and 13C-NMR, IR, HRMS, and single-crystal X-ray diffraction. Connections in the packing crystal structure of sensor R1 occur through hydrogen bonding interactions. However, no π-π stacking interactions between molecules of sensor R1 were observed. Addition of fluoride ion to a solution of sensor R1 resulted in the appearance of a new absorption band at 310 nm, which corresponded to the deprotonated species, and quenching of the peak at an emission wavelength of 562 nm. For the addition of other anions, there was a slight decrease in corresponding peaks in the UV-visible and emission spectra of sensor R1. According to the 1H-NMR study, the aromatic proton resonances of sensor R1 shifted upfield when adding fluoride ion. Analysis of the solutions prepared using Job’s method revealed that the complexation ratio of the complex formed between sensor R1 and fluoride ion was 1:1. The Stern−Volmer quenching constant (Ksv) between sensor R1 and fluoride ion was characterized as 7157 M−1.