Spectroscopic probing of the microenvironment of 7-oxy(5-selenocyanato-pentyl)-2H-1-benzopyran-2-one in ionic and nonionic micelles

• Modulation of photophysics in different micellar assembly.
• Rotational behavior in confined media.
• Dramatic enhancement of the PCM fluorescence in the CTAB micelles upon addition of quencher.
• Ion exchange phenomenon operative at the micelle surface.
• Development of highly polarity sensitive fluorescence molecular probe.

Entrapping of a drug molecule having prospective therapeutic activity in microhetrogeneous environments and modulating important photophysical properties is of immense importance in various potential applications. The photophysical properties of a newly synthesized bioactive 7-oxy(5-selenocyanato-pentyl)-2H-1-benzopyran-2-one (PCM) has been studied in micellar solutions of anionic sodium dodecyl sulfate (SDS), cationic cetyl trimethyl ammonium bromide (CTAB) and nonionic p-tert-octylphenoxy polyoxyethanol (TX-100) micelle using steady state, time resolved fluorescence and fluorescence anisotropy techniques. The present effort illustrates the degree of accessibility of the fluorophore toward the heavy ion quencher in the presence of micelles of different surface charge characteristics. Iodide induced quenching leads to a decrease in the fluorescence intensity in case of SDS and TX-100 micelles, where as in CTAB micelles enhancement of fluorescence intensity is observed. Quantitative estimation of the micropolarity at the binding site of the probe has been determined. The imposed motional restriction of the microenvironment around the probe has been established from environment dependent fluorescence parameter, fluorescence anisotropy (r) value.