ESIPT-inspired benzothiazole fluorescein: Photophysics of microenvironment pH and viscosity

• Synthesized novel ESIPT Inspired compounds which are unknown to this date, synthesis route is very easy and reproducible.
• Existing fluorescein compounds shows 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 were investigated.
• Experimental photophysical properties were compared with TD-DFT computational data.

A series of novel substituted ESIPT benzothiazole fluorescein derivatives were synthesized from the intermediate, (1H-benzo[d]thiazole-2-yl) benzene-1,3-diol and different anhydrides. The photophysical properties of these fluorescein derivatives were studied as a function of pH and viscosity. Enhancement in fluorescence emission was observed with increasing percentage of glycerin in water. The relative fluorescence quantum yields of these derivatives were determined by using anthracene and fluorescein as a reference standards. Density Functional Theory computations were performed to optimize the geometry at the ground state. The excited state geometry was optimized using the time dependent-DFT. The synthesized fluorescein derivatives were characterized by using elemental analysis, FT-IR and 1H NMR spectroscopy.

ESIPT inspired benzothiazole based fluorescein derivatives were synthesized by reacting the intermediate, (1H-benzo[d]thiazole-2-yl) benzene-1,3-diol with different substituted anhydrides. Effects of pH and viscosity on photophysical characteristics of ESIPT fluorescein derivatives were studied. Experimental photophysical properties were compared with density functional theory calculations.Figure optionsDownload as PowerPoint slide