Bioinspired energy conversion

TL;DR: In this paper, a new antenna reaction center complex is described in which a carotenoid moiety is located in partial conjugation with the tetrapyrrole π-system allowing fast energy transfer between the chromophores.

Abstract: Artificial photosynthetic antenna systems have been synthesized based on carotenoid polyenes and polymer-polyenes covalently attached to tetrapyrroles. Absorption of light in the blue/green region of the spectra excites the polyenes to their S 2 state, and ultra- fast singlet energy transfer to the tetrapyrroles occurs when the chromophores are in partial conjugation. The additional participation of other excited states of the polyene in the energy- transfer process is a requirement for perfect antenna function. Analogs of photosynthetic re- action centers consisting of tetrapyrrole chromophores covalently linked to electron accep- tors and donors have been prepared. Excitation of these constructs results in a cascade of energy transfer/electron transfer which, in selected cases, forms a final charge-separated state characterized by a giant dipole moment (>150 D), a quantum yield approaching unity, a sig- nificant fraction of the photon energy stored as chemical potential, and a lifetime sufficient for reaction with secondary electron donors and acceptors. A new antenna-reaction center complex is described in which a carotenoid moiety is located in partial conjugation with the tetrapyrrole π-system allowing fast energy transfer (<100 fs) between the chromophores. In this assembly, the energy transduction process can be initiated by light absorbed by the poly- ene.