Synthesis and photochemistry of a new benzothiazolinic oxazine salt and its application in the detection of hydrogen sulfate ion

Abstract

Although benzothiazolinic spiropyrans are reported in the literature, a benzothiazolinic oxazine has not been investigated. Therefore, a new photochromic benzothiazolinic oxazine in the salt form was successfully synthesized, and its structure was determined using single-crystal X-ray diffraction, 1H NMR, 13C NMR, IR, and other techniques. The results of X-ray diffraction show that oxazine is present in the open protonated form linked to a chloride ion. The benzothiazolinic oxazine detected the presence of HSO4- ion in an aqueous solution using UV–vis spectroscopy and provided a limit of the detection value of 1.58 µM. The complex formation was also probed using 1H NMR and HR-MS techniques. The structure of the benzothiazolinic probe was observed to be altered by 365 nm light. Unlike conventional photochromic oxazines, benzothiazolinic oxazine displayed greater stability of the open form in an aqueous solution and the closed form was observed after exposure to UV light (365 nm). The computational method (PW6B95D3/6-31G(d,p)) was correlated with the experimental data.