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Article

Static and Dynamic Quenching of Ru(II) Polypyridyl Excited States by Iodide

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Andras Marton, Christopher C. Clark, Ramya Srinivasan, Robert E. Freundlich, Amy A. Narducci Sarjeant, and Gerald J. Meyer*

Departments of Chemistry and Materials Science and Engineering, Johns Hopkins University, Baltimore, Maryland 21218

Inorg. Chem., 2006, 45 (1), pp 362–369

DOI: 10.1021/ic051467j

Publication Date (Web): December 10, 2005

Author to whom correspondence should be addressed. E-mail: meyer@jhu.edu.

Abstract

The metal-to-ligand charge-transfer (MLCT) excited states of Ru(bpy)₂(deeb)(PF₆)₂, where bpy is 2,2-bipyridine and deeb is 4,4‘-(CO₂CH₂CH₃)₂-2,2‘-bipyridine, in dichloromethane were found to be efficiently quenched by iodide at room temperature. The ionic strength dependence of the UV−visible absorption spectra gave evidence for ion pairing. Iodide was found to quench the excited states by static and dynamic mechanisms. Stern−Volmer and Benesi−Hildebrand analysis of the spectral data provided a self-consistent estimate of the iodide−Ru(bpy)₂(deeb)²⁺ adduct in dichloromethane, K = 59 700 M^-¹. Transient absorption studies clearly demonstrated an electron-transfer quenching mechanism with transient formation of I₂^•^- in high yield, phi = 0.25 for 355 or 532 nm excitation. For Ru(bpy)₂(deeb)(PF₆)₂ in acetonitrile, similar behavior could be observed at higher iodide concentrations than that required in dichloromethane. The parent Ru(bpy)₃²⁺ compound also ion pairs with iodide in CH₂Cl₂, and light excitation gave a higher I₂^•^- yield, phi = 0.50. X-ray crystallographic, IR, and Raman data gave evidence for interactions between iodide and the coordinated deeb ligand in the solid state.

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Published In Issue January 09, 2006
Received August 26, 2005

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Article

Static and Dynamic Quenching of Ru(II) Polypyridyl Excited States by Iodide

Abstract

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Dye Dependent Regeneration Dynamics in Dye Sensitized Nanocrystalline Solar Cells: Evidence for the Formation of a Ruthenium Bipyridyl Cation/Iodide Intermediate

High-Extinction Ruthenium Compounds for Sunlight Harvesting and Hole Transport

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