Redox reactivity of photogenerated osmium(II) complexes |
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Authors: | Dempsey Jillian L Winkler Jay R Gray Harry B |
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Institution: | Beckman Institute, California Institute of Technology, 1200 E. California Blvd., MC 139-74, Pasadena, California 91125, USA. |
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Abstract: | Powerful reductants Os(II)(NH(3))(5)L](2+) (L = OH(2), CH(3)CN) can be generated upon ultraviolet excitation of relatively inert Os(II)(NH(3))(5)(N(2))](2+) in aqueous and acetonitrile solutions. Reactions of photogenerated Os(II) complexes with methyl viologen to form methyl viologen radical cation and Os(III)(NH(3))(5)L](3+) were monitored by transient absorption spectroscopy. Rate constants range from 4.9 × 10(4) M(-1) s(-1) in acetonitrile solution to 3.2 × 10(7) (pH 3) and 2.5 × 10(8) M(-1) s(-1) (pH 12) in aqueous media. Photogeneration of five-coordinate Os(II) complexes opens the way for mechanistic investigations of activation/reduction of CO(2) and other relatively inert molecules. |
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