Pyrene-derived benzimidazoles as fluorescent sensors for detection of fluoride anion

Fluoridated water is widely used all over the world for decreasing tooth decay among the population. According to World Health Organization (WHO), dental caries is a major oral health problem in most industrialized countries affecting 60-90% of schoolchildren and the vast majority of adults. On the other hand, high concentrations of fluoride anion can cause dental fluorosis and even skeletal fluorosis. The optimal level of fluoride in drinking water is still not exactly known and recommended concentration varies from country to country. Thus, determination of fluoride is very important. Among all methods of determination of fluoride, the use of fluorescent sensors is most mobile and fast approach. Herein we report on synthesis and some sensing properties of pyrene-derieved 1H- benzimidazoles 2 and investigating their ability to determine fluoride anion qualitatively. Compound 2a has shown specific reaction to the fluoride anion which consisted in changing of emission color from bright blue to yellowish. Solution color has also changed from pale yellow to orange. All the other compounds have shown slight changes in case of cyanide ion or no changes at all.