title: Structural, electrochemical and photophysical properties of an exocyclic di-ruthenium complex and its application as a photosensitizer.
abstract: The reaction of cis-bis(2,2'-bipyridine)dichlororuthenium(ii) hydrate with a conformationally mobile bipyridyl macrocycle afforded [(bpy)2Ru(μ-L)Ru(bpy)2]Cl4·6H2O, a bridged di-Ru complex. Single crystal X-ray diffraction showed the macrocyclic ligand adopting a bowl-like structure with the exo-coordinated Ru(ii) centers separated by 7.29 Å. Photophysical characterization showed that the complex absorbs in the visible region (λmax = 451 nm) with an emission maximum at 610 nm (τ = 706 ns, ΦPL = 0.021). Electrochemical studies indicate the di-Ru complex undergoes three one-electron reversible reductions and a reversible one-electron oxidation process. This electrochemical reversibility is a key characteristic for its use as an electron transfer agents. The complex was evaluated as a photocatalyst for the electronically mismatched Diels-Alder reaction of isoprene and trans-anethole using visible light. It afforded the expected product in good conversion (69%) and selectivity (dr > 10 : 1) at low loadings (0.5-5.0 mol%) and the sensitizer/catalyst was readily recycled. These results suggest that the bipyridyl macrocycle could be widely applied as a bridging ligand for the generation of chromophore-catalyst assemblies.
authors.affiliation: Department of Chemistry and Biochemistry, University of South Carolina, Columbia, SC 29208, USA. shimizls@mailbox.sc.edu.
authors.forename: Sahan R
authors.initials: SR
authors.lastname: Salpage
authors.forename: Avishek
authors.initials: A
authors.lastname: Paul
authors.forename: Bozumeh
authors.initials: B
authors.lastname: Som
authors.forename: Tanmay
authors.initials: T
authors.lastname: Banerjee
authors.forename: Kenneth
authors.initials: K
authors.lastname: Hanson
authors.forename: Mark D
authors.initials: MD
authors.lastname: Smith
authors.forename: Aaron K
authors.initials: AK
authors.lastname: Vannucci
authors.forename: Linda S
authors.initials: LS
authors.lastname: Shimizu