Synthesis of multi-porphyrin dendrimer as artificial light-harvesting antennae

To mimic bacterial light-harvesting antenna complexes, a series of dendritic multi porphyrin arrays, nP(Zn)-P-FB (n = 2, 4; cone-shaped dendrimers, n = 8, 16; star-shaped dendrimers), were synthesized and characterized by H-1 NMR and MALDI-TOF-MS spectroscopy. Photoinduced energy-transfer efficiency (F ET) from peripheral Zn porphyrin (P-Zn) units to an inner core free-base porphyrin (P-FB) in the dendrimers was evaluated by fluorescence measurement. Both star-and cone-shaped multi-porphyrin arrays exhibited significantly high efficiency energy transfer from the photoexcited P-Zn units to the energy-accepting P-FB, where the star-shaped dendrimers, 8P(Zn)-P-FB (94%) and 16P(Zn)-P-FB (88%), had a slightly higher efficiency than those of the cone-shaped dendrimers, 2P(Zn)-P-FB (92%) and 4P(Zn)-P-FB (80%), respectively.