PHOTOINDUCED INTRAMOLECULAR CHARGE-TRANSFER IN DIPHENYLAMINO-SUBSTITUTED TRIPHENYLBENZENE, BIPHENYL, AND FLUORENE

The photophysical properties of a diphenyl amino-substituted triphenyl benzene, (pEFTP), biphenyl (pEFBP), and fluorene (pEFF) derivative are compared. The similarity of the photophysical properties and their so lvent dependence for the triphenylbenzene and the biphenyl model compo und indicate the formation of a polar excited state, localized in one branch of pEFTP. Further comparison with the fluorene model compound s uggests an excited state relaxation process of the biphenyl moiety in solvents of medium and high polarity toward a more planar geometry. Th e depopulation of the excited state is explained in the framework of t he model developed to rationalize the photophysics of substituted biph enyl.