Axially Assembled Photosynthetic Antenna-Reaction Center Mimics Composed of Boron Dipyrromethenes, Aluminum Porphyrin, and Fullerene Derivatives.

Sequential photoinduced energy transfer followed by electron transfer leading to the formation of charge separated states in a newly assembled series of supramolecular triads comprised of boron dipyrromethenes (BODIPY or BDP), aluminum porphyrin (AlTPP) and C is demonstrated. In the present strategy, the energy donor (BDP) and electron acceptor (C) were axially positioned to the plane of AlTPP via the central metal. The structural integrity of the newly synthesized compounds and self-assembled systems were fully established using spectral, electrochemical and computational methods. Thermodynamic feasibility of energy transfer from BDP* to AlTPP and subsequent electron transfer from AlTPP* to generate BDP-AlTPP-C charge separated states was derived from free-energy calculations. Occurrence of ultrafast energy transfer from BDP* to AlTPP was established from studies involving steady-state and time-resolved emission, as well as femtosecond transient spectroscopic techniques. The BDP-AlTPP-C charge separated states persisted for several nanoseconds prior returning to the ground state.