Energy Transfer Among Like and Unlike Molecules in Solution VI. Effect of the Mediation of Donor Molecules Upon the Electronic Excitation Energy Transfer in Binary Systems

The effect of an interdonor energy transfer is investigated on the following donor-acceptor systems in thin rigid cellulose acetate films: anthracene and tetracene (I), 9-methylanthracene and 2-aminobenzophenone (II), 9,10-diphenylanthracene and 2-aminobenzophenone (III). The donor quantum yield and fluorescence anisotropy in systems I-III are in good agreement with theoretical predictions for a model of a multi-step excitation energy transfer process. In mixed two-component solutions the donor fluorescence anisotropy is higher than in single-component solutions, indicating an interdonor excitation transfer preceding the donor-acceptor transfer in these binary systems.