U-shaped donor [bridge] acceptor systems with remarkable charge transfer fluorescent properties: An experimental and computational investigation.

The photoinduced intramolecular electron transfer in two donor−bridge−acceptor systems was studied using (time-resolved) fluorescence and transient absorption techniques. DPN[8cy]DCV and DPMN[8cy]DCV consist of a 1,4-diphenylnaphthalene (DPN) and a 1,4-diphenyl-5,8-dimethoxynaphthalene (DPMN) electron donor, respectively, and the 1,1-dicyanovinyl acceptor (DCV) in both systems. The overall geometry of the saturated hydrocarbon bridge is U-shaped, separating the donor and acceptor by an 8-σ-bond through-bond distance and a 5.8 A (center-to-center) through-space distance in the ground state. In all solvents fast electron transfer is observed in both systems resulting in a fluorescent charge transfer (CT) state. Especially for DPN[8cy]DCV CT fluorescence can be detected over a wide range of solvent polarity. The solvent dependence of the CT fluorescence position, lifetime, and quantum yield could thus be employed to estimate the solvent effect on the dipole moment of the CT state, the rate of charge recombin...