Spectroscopic Properties of Quercetin-3-O-rhamnoside and Quercetin-3-O-rutinoside in Aerosol-OT Reverse Micelles

Abstract

The anomalous spectroscopic properties of quercetin-3-O-rhamnoside (QCRM) and quercetin-3-O-rutinoside (QCRT) in AOT reverse micelle were studied. The excited state intramolecular proton transfer (ESIPT) occurs through the strong hydrogen bond between the -OH at position 5 and the carbonyl oxygen. Because the ESIPT can only happens in the S-1 state and the Franck-Condon factor involved in the S-2 --> S-1 internal conversion is small, the S-2 --> S-1 emission alone appears. Because the molecular planarity is improved at the interior of the micelle, the excited state intramolecular charge transfer in the S-1 state is extended, and the excited state is more tolerable for any quenching effects in the micelle. Therefore, an S-1 --> S-o emission was newly discovered under this micelle microenvironment. For the S-2 --> S-o emission, the quantum yields increase but the quantum yield of the S-1 --> S-o emission approximately decreases as the water concentration in the micelle increases.