Symmetry breaking charge transfer processes of zinc dipyrrin complexes

Photoinduced charge transfer (CT) via symmetry breaking (SB) processes plays a crucial role in photosynthetic reaction center of biol. systems. In such systems, which contain two or more identical and sym. chromophores, CT process from one to another chromophore occurs upon photo-excitation, thus breaking the symmetry. It is of great interest to apply SBCT processes in org. photovoltaics (OPV) and related systems. For application to OPVs, it is desirable for compds. that undergo SB processes to have absorption in the visible spectrum. The most well-documented compds. for SB phenomenon, such as bianthryl derivs., do not absorb visible light. Herein we present study on Zinc Dipyrrin complexes, which contain two identical dipyrrin ligands and absorb strongly at 450-550 nm. These compds. undergo efficient SBCT processes in polar solvents; the photoinduced CT state from the singlet excited state occurs in 4-7 ps, and then recombines back to the triplet state in 1-4 ns.