Flattened Calixarene-like Cyclic BODIPY Array: A New Photosynthetic Antenna Model

A cyclic BODIPY array, characterized by a rigid flattened calixarene-like conformation, acts as a photosynthetic antenna mimic. The system in question, triBODIPY, is a better antenna than the corresponding BF₂-free ligand. On the basis of absorption spectral studies and supporting calculations, it is concluded that exciton coupling between the BODIPY subunits occurs readily. TriBODIPY supports a complex with Li⁺@C₆₀ that bring an antenna-like light absorber into close proximity to an electronic acceptor without the need for linking spacers. As inferred from X-ray diffraction analyses of complexes between triBODIPY and C₆₀, it is inferred that the fullerene complexes are stabilized via convex-concave donor-acceptor interactions. Steady state absorption/fluorescence, time-correlated single photon counting, and transient absorption measurements have allowed a complete characterization of the complexes in both the ground and excited states, including the host-guest recognition features, fluorescence quenching effects, and charge separation/recombination dynamics.