Environment-sensitive benzoxazole based fluorescein derivatives: Synthesis and application to the design of ON–OFF fluorescent chemosensors for microenvironment

The intermediate 2-(2′, 4,-dihydroxyphenyl) benzoxazole was used for the synthesis of substituted fluorescein derivatives. Fluorescence behavior of the synthesized fluorescein derivatives was studied under different microenvironments like pH, viscosity, surfactant sodium dodecyl sulfate (SDS) and protein Bovine Serum Albumin (BSA). Further, the fluorescence of these molecules was used for the detection of blood sample. Photophysical properties show that all the fluorescent compounds are very sensitive to pH, and in basic medium these compounds show hyper chromic shift. These compounds are also sensitive to the viscosity of the medium. All the compounds are characterized by FT-IR, H NMR and mass spectral analysis. •Synthesized novel ESIPT inspired compounds which are unknown to this date, synthesis route is very easy.•Existing fluorescein compounds show single absorption in UV region having restricted applications are overcome by introducing ESIPT unit in fluorescein core.•First and unique study of fluorescein compounds having pH sensitive dual absorption–emission characteristics.•Relative fluorescence quantum yield of fluorescein derivatives was investigated.