Photoinduced Cascading Charge Transfer in Perylene Bisimide-Based Triads

We synthesize three perylene bisimide-based triads with donor-acceptor-acceptor (D-A(1)-A(2)) architectures, in which the distance between D and A(1) is varied to study its influence on the excited state electron processes. Very different intramolecular charge transfer (D+similar to A(1)-A(2)-) lifetimes in dichloromethane (DCM) for these three triads are revealed by steady-state and transient spectroscopies. Free-energy changes of charge transfer (CT) are calculated based on the single-crystal X-ray diffraction data and electrochemical measurements. The results show that photoinduced cascading CT comprises two competing processes in DCM (CTs in D similar to A(1) units and in A(1)-A(2) units) by pumping of the A(1) unit, and then the long-distance CT state is formed. The charge recombination (CR) process is restrained effectively by the increased distance between the anion and cation. This research reveals the importance of multistep cascading CTs on tuning the CT lifetime in multichromophoric systems.

Automated summary

We synthesized perylene bisimide-based triads with different distances between donor and acceptor to study their influence on excited state electron processes. Different charge transfer lifetimes were observed in dichloromethane for these triads. Through calculation of charge transfer free-energy changes, it was found that cascading charge transfer processes play an important role in tuning charge transfer lifetime in multichromophoric systems.