Excited-State Intramolecular Proton Transfer and Charge Transfer Fluorescence of a 3-Hydroxyflavone Derivative in AOT Reverse Micelles

摘要

We have investigated the fluorescence emission behaviour of 4' -N, N-dimethylamino-3-hydroxyflavone DMA3HF in reverse micelles of AOT in n-heptane at different water / surfactant molar ratio (w_0). DMA3HF encompasses proton transfer (PT) as well as charge transfer (CT) fluorescence in a single molecular system. Both these emissions are prominent in DMA3HF solubilized in AOT reverse micelles, with emission maxima occurring at 449 nm and 552 nm for the CT and PT bands respectively at w_0 = 0. The PT fluorescence may be attributed to a ground state population of DMA3HF located in the apolar phase of the reverse micelles, while the CT fluorescence appears to originate from the DMA3HF molecules residing in the interfacial region, proximal to the AOT head groups. As w_0 is increased, the yield of PT fluorescence is enhanced, while the CT fluorescence undergoes a decrease in emission yield, together with dramatic red shifts in #lambda#_(max)~(em). These results along with fluorescence anisotropy, REES and fluorescence lifetime data have been used to probe the microenvironments of the DMA3HF molecules in the reverse micelles.