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Electronic structures, photophysical properties, and electrochemistry of ruthenium(II)(bpy)_2 pyridylimidazole complexes

Lancaster, Kyle M. and Gerken, James B. and Durrell, Alec C. and Palmer, Joshua H. and Gray, Harry B. (2010) Electronic structures, photophysical properties, and electrochemistry of ruthenium(II)(bpy)_2 pyridylimidazole complexes. Coordination Chemistry Reviews, 254 (15-16). pp. 1803-1811. ISSN 0010-8545.

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The properties of Ru^(II) complexes involving the imidazole moiety are discussed. Complexes [Ru(bpy)_2(L)]^(2+) [bpy = 2,2′-bipyridine, L = 2-(2′-pyridyl)imidazole (2-pimH) and 4-(2′-pyridyl)imidazole (4-pimH)] have been synthesized and fully characterized. Reduction potentials are 0.76 V vs. Fc^+/Fc^0 for both complexes in acetonitrile solution, and the deprotonated complexes undergo irreversible electrochemical oxidation at 0.38 V vs. Fc^+/Fc^0. Density functional theory (DFT) calculations suggest that oxidation of the protonated complexes is primarily metal-based and that of the deprotonated complexes is ligand-centered. The pK_a of the 4-pimH complex was found to be 9.7 ± 0.2; the pK_a of the 2-pimH complex is 7.9 ± 0.2. Luminescence lifetimes (L = 4-pimH, 277 ns; 2-pimH, 224 ns; 4pim^−, 40 ns; 2pim^−, 34 ns in 5% methanol/water solution) combined with quantum yield data and acid–base behavior suggest that the non-coordinated imidazole nitrogen tunes deactivation pathways.

Item Type:Article
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Lancaster, Kyle M.0000-0001-7296-128X
Gray, Harry B.0000-0002-7937-7876
Additional Information:© 2010 Published by Elsevier B.V. Received 20 August 2009; accepted 9 April 2010. Available online 24 April 2010. We thank Jay Winkler and Theis Brock-Nannestad for discussions. We thank Tony Vlček for a critical reading of this manuscript. We also thank John D. Roberts and Brian Stoltz for the kind loan of reagents and equipment. This work was supported by the NSF Center for Chemical Innovation (Powering the Planet, CHE-0802907 and CHE-0947829), the Arnold and Mabel Beckman Foundation, and CCSER (Gordon and Betty Moore Foundation).
Group:CCI Solar Fuels
Funding AgencyGrant Number
Arnold and Mabel Beckman FoundationUNSPECIFIED
Gordon and Betty Moore FoundationUNSPECIFIED
Subject Keywords:Ruthenium; Pyridylimidazoles; Photophysics; Cyclic voltammetry
Issue or Number:15-16
Record Number:CaltechAUTHORS:20100804-134627105
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:19276
Deposited By: Tony Diaz
Deposited On:04 Aug 2010 21:03
Last Modified:16 Nov 2020 18:02

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