Mimicking photosynthetic antenna-reaction-center complexes with a (Boron Dipyrromethene) 3-Porphyrin-C 60 pentad

Abstract

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 .+-C 60 .-, which has a lifetime of 476 and 1000a ps in benzonitrile and toluene, respectively. Interestingly, a slow charge-recombination process (κ T CR=2.6×10 6a s -1) and a long-lived triplet charge-separated state (τ T CS=385 ns) were detected in polar benzonitrile by nanosecond transient measurements. Good combination! Covalent linkage of three boron dipyrromethene units, a zinc(II) porphyrin core, and a C 60 moiety results in the formation of a novel pentad (see figure) which can mimic the efficient processes of energy transfer followed by electron transfer occurring in photosynthetic antenna-reaction-center complexes. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.