Spectroscopic Properties of Morin in Various CH^sub 3^OH-H^sub 2^O and CH^sub 3^CN-H^sub 2^O Mixed Solvents

The specific fluorescence properties of morin (3,2',4',5,7-pentahydroxyflavone) were studied in various ... and ... mixed solvents. Although the dihedral angle is large in the ... state, morin has an almost planar molecular structure in the ... state owing to the very low rotational energy barrier around the interring bond between B and the A, C ring. The excited state intramolecular proton transfer (ESIPT) at the ... state cannot occur immediately after excitation, ... fluorescence can be observed. Two conformers, Morin A and B have been known. At the ..., Morin B will be the principal species but at the ..., Morin A is the principal species. At the ..., owing to the large Franck-Condon (FC) factor for ... internal convernal (IC) and flexible molecular structure, only ... fluorescence was exhibited. At the ..., as the FC factor for ... is small and molecular structure is rigid, ... and ... dual fluorescence was observed. This abnormal fluorescence property was further supported by the small pK... value, effective delocalization of the lone pair electrons of C(2')-OH to the A, C ring, and a theoretical calculation. (ProQuest: ... denotes formulae/symbols omitted.)