PHOTOCHEMICAL ENERGY-CONVERSION IN A HELICAL OLIGOPROLINE ASSEMBLY

A general method is described for constructing a helical oligoproline assembly having a spatially ordered array of functional sites protrudi ng from a proline-II helix, Three different redox-active carboxylic ac ids were coupled to the side chain of cis-4-amino-L-proline. These red ox modules were incorporated through solid-phase peptide synthesis int o a 13-residue helical oligoproline assembly bearing in linear array a phenothiazine electron donor, a tris(bipyridine)ruthenium(II) chromop hore, and an anthraquinone electron acceptor, Upon transient 460-nm ir radiation in acetonitrile, this peptide triad formed with 53% efficien cy an excited state containing a phenothiazine radical cation and an a nthraquinone radical anion, This light-induced redox-separated state h ad a lifetime of 175 ns and stored 1.65 eV of energy.