Photochemistry of deca(acetonitrile) dirhodium(II) cation: evidence for kilosecond-lived photoinduced charge separation
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Events following the photodissociation of the dinuclear rhodium(II,II) complex Rh2L10 (L = CH3CN), are reported. Spectroscopic and electrochemical evidence demonstrates that this complex possesses novel reversible photochemistry with metastable photoproducts that exist for kiloseconds after photodissociation, and ultimately regenerate the original dimer. UV/Vis irradiation of acetonitrile solutions of the complex results in homolytic cleavage of the Rh-Rh bond to give a promptly formed paramagnetic transient that EPR evidence suggests to be Rh(II)L6. This species has a half-life of ca. 50 s, and initiates a reaction sequence that generates photodisproportionated, metastable products, which are inferred to be Rh(III)L6 and Rh3(II,II,I)Ln These products have half-lives in the kilosecond range. The proposed photochemical processes thus achieve photoinduced charge separation, with remarkably long lifetimes for the charge-separated species. The metastable species may be viewed as a photogenerated electron-hole pair in solution that, due to its long lifetimes, may have significant potential in converting light into usable chemical energy.
author list (cited authors)
James, C. A., Morris, D. E., Doorna, S. K., Arrington, C. A., Dunbar, K. R., Finnis, G. M., Pence, L. E., & Woodruff, W. H.