Visible light-harvesting in covalently-linked porphyrin-cyanine dyes

We report the synthesis and properties of three members of a new class of photochemical model compounds containing a covalently-linked porphyrin and a cyanine dye. In compounds 1 and 2 the dye absorbs in the 450–570 nm region and energy transfer occurs with 80% efficiency from the dye to the free base porphyrin. In compound 3 the dye absorbs in the 650–780 nm region and energy transfer occurs with 80% efficiency from the free base porphyrin to the dye . The zinc-porphyrin-dyes exhibit both donor and acceptor quenching with only moderate yields of energy transfer. This work is a first step toward the development of an artificial phycobilisome.