New Styryl 1,3,4-Oxadiazol-Based Fluorometric "Turn on" pH Sensor

A new 1,3,4-oxadiazole derivative (MeO-SODA) was synthesized, fully characterized by means of IR, NMR and HRMS data and and additionally, its ability to detect extremely acidic pH values ​​was examined. Firstly, the characteristic behavior of MeO-SODA was examined in ten different solvents, revealing that it underwent non-radiative transitions as the hydrogen bonding capacity of solvent increased. Secondly, the absorption and fluorescence measurements for MeO-SODA were conducted across various pH levels (pH 2, 4, 6, 7, 9, 10, 12), with fluorescence emission observed exclusively at pH 2. We propose that this new probe could serve as a highly selective sensor at extremely acidic pH levels. Additionally, experiments with lemon juice demonstrated that this new 1,3,4-oxadiazole derivative could be suitable for practical applications. Furthermore, the results of this study are expected to provide insights into synthesizing new probes capable of detecting at a single pH value, setting them apart from the typical pH studies found in the literature.