Dynamic Behaviors of the Electron Donor-Acceptor Complex in its Lowest Excited Singlet State

Dynamic behaviors of the weak electron donor-acceptor (EDA) complex in its lowest excited singlet state have been investigated by the nsec flash photolysis method and measurements of fluorescence and transient photocurrent. In polar solvents the weak EDA complex in its lowest excited singlet state dissociates spontaneously into ions. The dynamic behaviors of s-tetracyanobenzene(TCNB)-benzene and TCNB-toluene complexes were studied in some solvents and the existence of the direct radiationless process at the excited Franck-Condon (FC) state as well as in the course of relaxation process from the excited FC state to the fluorescent state has been confirmed in the case of 1,2-dichloroethane solution. The nature of the intra-complex radiationless processes was discussed on the basis of this result. It has been pointed out that the lifetime of excited states is of crucial importance for understanding the dynamic behaviors of excited weak EDA complexes.