Dynamics of Electron Transfer and Energy Transfer by Newly Synthesized Asymmetric Photosensitizer

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We newly synthesized chiral photosensitizers, Δ-[Ru(menbpy)ィイD23ィエD2]ィイD12+ィエD1 (menbpy=4,4'-bis(1R,2S,5R)-(-)menthoxycarbonyl}-2,2'-bipyridine), Δ-[Ru(phenebpy)ィイD23ィエD2]ィイD12+ィエD1 (phenebpy=4,4'-bis(1-phenethylaminocarbonyl)-2,2'-bipyridine), [Cu(tmdcbpy)(PRィイD23ィエD2)ィイD22ィエD2]ィイD12+ィエD1 (tmdcbpy=4,4'-6,6'-tetramethyl-5,5'-bis(S)-(-)-1-phenylcarbamoyl-2,2'-bipyridine).These photosensitizers do not cause photoracemization and their photoexcited states (triplet MLCT excited state) are long-lived, (2) Δ-[Ru(menbpy)ィイD23ィエD2]ィイD12+ィエD1 performs effectively stereoselective photoreduction of [Co(acac)ィイD23ィエD2] under visible light irradiation. [Cu(tmdcbpy)(PPhィイD23ィエD2)]ィイD1+ィエD1 also performs stereoselective photoreduction of [Co(edta)]ィイD1-ィエD1 with significantly large enantiomer excess (60% at l0% conversion), under near-UV light irradiation. On the other hand, [Ru(phenebpy)ィイD23ィエD2]ィイD12+ィエD1 cannot perform stereoselective photoreduction. (3) An anionic chiral Cu(I) complex, [Cu(tmdcb … More py){PPhィイD22ィエD2(m-CィイD26ィエD2HィイD24ィエD2SOィイD23ィエD2ィイD1-ィエD1)}ィイD22ィエD2]ィイD1-ィエD1, performs photoreduction of [Co(edta)]ィイD1-ィエD1 with less reactivity and smaller stereoselectivity. The reaction mechanism is different from that of photoreduction of [Co(edta)]ィイD1-ィエD1 by [Cu(tmdcbpy)(PPhィイD23ィエD2)ィイD22ィエD2]ィイD1+ィエD1. The former proceeds through dynamic quenching mechanism, while the latter through static quenching mechanism. (4) We succeeded the photoasymmetric synthesis of [Co(edta)]ィイD1-ィエD1 from CoXィイD22ィエD2 (X=AcOィイD1-ィエD1, NOィイD23ィエD2ィイD1-ィエD1 etc.) and LィイD24ィエD2edta (L=H or Na) with [Cu(tmdcbpy)(PPhィイD23ィエD2]ィイD1+ィエD1 under near-UV light irradiation. Δ-[Co(edta)]ィイD1-ィエD1 is formed in excess when NaィイD24ィエD2edta was used, while ∧-[Co(edta)]ィイD1-ィエD1 is formed when HィイD24ィエD2edta was used. (5) Photoderacemization of [Co(acac)ィイD23ィエD2] was successfully carried out with Δ-[Ru(menbpy)ィイD23ィエD2]ィイD12+ィエD1 in acetonitrile-water under visible light irradiation. The reaction mechanism was elucidated. (6) Stereoselective photoreduction of chiral viologen was successfully performed with Δ-[Ru(menbpy)ィイD23ィエD2]ィイD12+ィエD1 and analysis based on Marcus theory was presented. Less