Synthesis of bis[2-(2’-hydroxyphenyl)benzazole] derivatives as “Turn-on” fluorescent pH probes for detection of alkaline pH

Abstract

The pH is a very important parameter in several region such as human health, industry, and environment. For this reason, a lot of pH fluorescent probes have been studied to monitor various pH ranges. However, the number of fluorescent probes capable of detecting alkaline range is relatively small compared to their importance. In this work, we synthesized bis[2-(2’-hydroxyphenyl)benzazole] (bis(HBX)) derivatives and evaluated their properties to confirm that they could be used as fluorescent probes to monitor alkaline pH. The three bis(HBX) probes have high pKa values between 9.7 and 10.8 and show strong fluorescence intensities and color changes above pH 10. Also, these probes have properties as photostability, reversibility and anti-interference toward pH variation. Therefore, we envisioned that the bis(HBX) derivatives can be used as useful probes to identify fluorescence changes with pH in the basic range.