Intramolecular excited-state proton transfer and charge transfer fluorescence of a 3-hydroxyflavone derivative in micellar media

Abstract

The fluorescence emission behaviour of 4′- N,N-dimethylamino-3-hydroxyflavone (DMA3HF), has been examined in representative micellar media. The utility of this fluorophore as a novel micellar probe is demonstrated, exploiting various parameters of its excited-state intramolecular proton transfer (ESIPT) and charge transfer (CT) fluorescence. The intensity and polarization anisotropy of both ESIPT and CT fluorescence prove to be highly sensitive monitors for estimating the first and second critical micelle concentrations (CMC1 and CMC2). Furthermore, the CT fluorescence exhibits dramatic blue shifts in micelles, along with high values of polarization anisotropy and significant red edge excitation shift (REES). The results suggest that the fluorophore resides in highly polar, motionally constrained regions in the micelle interface.