Excitation energy transfer from BODIPY to self-aggregate of zinc bacteriochlorophyll-d analog in supramolecule

Abstract

In the main light-harvesting antennas (chlorosomes) of anoxygenic photosynthetic green bacteria, photoexcited carotenoids absorbing green light donate singlet excitation energy to self-aggregates of bacteriochlorophylls(BChls)-c/d/e with their site energies in a far-red light region. To mimic the energy transfer systems, a zinc BChl-d analog covalently linked with a boron dipyrromethene (BODIPY) derivative was investigated in 1%(v/v) tetrahydrofuran and hexane. In the less polar organic solvent, the Zn-BChl-d part in the conjugate self-aggregated similarly as in chlorosomes and accepted excitation energy from the BODIPY part with absorption around 500 nm in a green light region. The excitation energy transfer from BODIPY* to (Zn-BChl-d)_n in the supramolecular self-assembly of the conjugate was analyzed by visible absorption and fluorescence emission spectroscopy.