Mimicking electron transfer reactions in photosystem II : synthesis and photochemical characterization of a ruthenium(II) tris(bipyridyl) complex with a covalently linked tyrosine.

• In the natural photosynthetic reaction center photosystem II, absorption of a photon leads to photooxidationof the primary electron donor P680, which subsequently retrieves electrons from a tyrosyl residue, functioning as aninterface to the oxygen-evolving manganese complex. In a first step toward mimicking these reactions, we havemade a Ru(II)-polypyridine complex with an attached tyrosyl moiety. The photoexcited ruthenium complex playedthe role of P680and was first oxidized by external acceptors. Combined transient absorbance and EPR studies provided evidence that the Ru(III) formed was reduced by intramolecular electron transfer from the attached tyrosine, with a rate constant of 5104s-1. Thus we show that a tyrosine radical could be formed by light-induced electrontransfer reactions, and we indicate future directions for developing a closer analogy with the photosystem II reactions.

Subject headings

NATURVETENSKAP  -- Biologi (hsv//swe)

NATURAL SCIENCES  -- Biological Sciences (hsv//eng)

Keyword

Photosynthetic oxygen evolution

Y-Z

manganese cluster

excited-states

model

metal

PHOTOSYNTHETIC OXYGEN EVOLUTION

Y-Z

MANGANESE CLUSTER

EXCITED-STATES

MODEL

METAL

Publication and Content Type

ref (subject category)

art (subject category)