Mimicking Photosynthetic Antenna-Reaction-Center Complexes with a (Boron Dipyrromethene)(3)-Porphyrin-C-60 Pentad

A highly efficient functional mimic of the photosynthetic antenna-reaction-center complexes has been designed and synthesized. The model contains a zinc(II) porphyrin (ZnP) core, which is connected to three boron dipyrromethene (BDP) units by click chemistry, and to a C-60 moiety using the Prato procedure. The compound has been characterized using various spectroscopic methods. The intramolecular photoinduced processes of this pentad have also been studied in detail with steady-state and time-resolved absorption and emission spectroscopic methods, both in polar benzonitrile and nonpolar toluene. The BDP units serve as the antennae, which upon excitation undergo singlet singlet energy transfer to the porphyrin core. This is then followed by an efficient electron transfer to the C-60 moiety, resulting in the formation of the singlet charge-separated state (BDP)(3)-ZnP center dot+-C-60(center dot-), which has a lifetime of 476 and 1000 Ps in benzonitrile and toluene, respectively. Interestingly, a slow charge-recombination process (k(CR)(T)=2.6 x 10(6) s(-1)) and a long-lived triplet charge-separated state (tau(T)(CS)=385 ns) were detected in polar benzonitrile by nanosecond transient measurements.