Organochalcogen substituted dimesityl borane-imidazoles as fluorogenic fluoride and cyanide sensors in aqueous media

• Published in: Analyst (London) 2023-05, Vol.148 (1), p.2362-2374
• Main Authors: Parveen, Sabeeha, Naaz, Farha, Prasad, Dasari L. V. K, Anantharaman, Ganapathi
• Format: Article
• Language: English
• Subjects: Anions; Aqueous solutions; Binding; Crystallography; First principles; Fluorides; Halides; Imidazole; Quantum mechanics; Sensors; Single crystals; Substrates
• ISSN: 0003-2654; 1364-5528
• DOI: 10.1039/d2an02095e

Natural and anthropogenic activities leading to excessive toxic biological anions in water have warranted the development of anion sensors, especially for cyanide (CN − ) and fluoride (F − ) ions in aqueous media. Herein, a contemporary synthetic route to embed organochalcogen compounds (-SPh and -SePh) in a boron-functionalized imidazole scaffold via metal halogen exchange is reported. Upon methylation, fluorogenic compounds 5-dimesitylboryl-2-phenylthio-1-methylimidazole ( 7 ) and 5-dimesitylboryl-2-phenylselone-1-methylimidazole ( 8 ) form the corresponding imidazolium salts, 5-dimesitylboryl-2-phenylthio-1-methylimidazolium iodide ( 9 ) and 5-dimesitylboryl-2-phenylselone-1-methylimidazolium iodide ( 10 ), which are non-luminescent. All of the compounds are thoroughly characterized, and their utility in sensing F − , CN − , and various other biologically relevant halides has been studied through UV-vis and fluorescence spectroscopy. The substrates and products of 1 : 1 binding of anions (F − /CN − ) with the compounds have been established by spectroscopy, spectrometry, single-crystal X-ray crystallography, and first principles quantum mechanical theoretical calculations. The superior binding ability and micromolar sensitivity towards CN − ions over other anions in aqueous media were elucidated. The reversibility of compound 7 was also tested and it was found that fluoride binding was reversible while cyanide binding was not. Various sustainable fluorogenic anion sensors based on organochalcogens (-SPh, -SePh) substituted imidazole borane scaffolds, which particularly detect F − and CN − over other biologically relevant ions in competitive aqueous media are reported.