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Transient Absorption Spectroscopy of Ruthenium and Osmium Polypyridyl Complexes Adsorbed onto Nanocrystalline TiO_2 Photoelectrodes

Kuciauskas, Darius and Monat, Jeremy E. and Villahermosa, Randy and Gray, Harry B. and Lewis, Nathan S. and McCusker, James K. (2002) Transient Absorption Spectroscopy of Ruthenium and Osmium Polypyridyl Complexes Adsorbed onto Nanocrystalline TiO_2 Photoelectrodes. Journal of Physical Chemistry B, 106 (36). pp. 9347-9358. ISSN 1520-6106. doi:10.1021/jp014589f.

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Transient absorption spectroscopy has been used to probe the electron injection dynamics of transition metal polypyridyl complexes adsorbed onto nanocrystalline TiO_2 photoelectrodes. Experiments were performed on photoelectrodes coated with Ru(H_2L‘)_2(CN)_2, Os(H_2L‘)_2(CN)_2, Ru(H_2L‘)_2(NCS)_2, or Os(H_2L‘)_2(NCS)_2, where H_2L‘ is 4,4‘-dicarboxylic acid-2,2‘-bipyridine, to study how the excited-state energetics and the nature of the metal center affect the injection kinetics. All of these complexes exhibited electron injection dynamics on both the femtosecond and picosecond time scales. The femtosecond components were instrument-limited (<200 fs), whereas the picosecond components ranged from 3.3 ± 0.3 ps to 14 ± 4 ps (electron injection rate constants k_2‘ = (7.1−30) × 10^(10) s^(-1)). The picosecond decay component became more rapid as the formal excited-state reduction potential of the complex became more negative. Variable excitation wavelength studies suggest that femtosecond injection is characteristic of the nonthermalized singlet metal-to-ligand charge-transfer (^1MLCT) excited state, whereas picosecond injection originates from the lowest-energy ^3MLCT excited state. On the basis of these assignments, the smaller relative amplitude of the picosecond component for the Ru sensitizers suggests that electron injection from nonthermalized excited states competes more effectively with ^1MLCT → ^3MLCT conversion for the Ru sensitizers than for the Os sensitizers.

Item Type:Article
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URLURL TypeDescription
Kuciauskas, Darius0000-0001-8091-5718
Gray, Harry B.0000-0002-7937-7876
Lewis, Nathan S.0000-0001-5245-0538
Additional Information:© 2002 American Chemical Society. Received: December 18, 2001; In Final Form: April 8, 2002; Publication Date (Web): August 17, 2002. This work was supported by the Department of Energy, Office of Basic Energy Sciences, Grants DE-FG03-88ER13932 (D.K., N.S.L.) and DE-FG03-96ER14665 (JKM); by the NSF (H.B.G.); by the University of California Energy Institute (JKM); by the Petroleum Research Fund administered by the American Chemical Society, grant 36108-AC6 (JKM); and by the Alfred P. Sloan Foundation (JKM). We also acknowledge a generous gift in support of work on TiO_2 photoelectrochemistry to Caltech by the DuPont Company.
Funding AgencyGrant Number
Department of Energy (DOE)DE-FG03-88ER13932
Department of Energy (DOE)DE-FG03-96ER14665
University of California Energy InstituteUNSPECIFIED
American Chemical Society Petroleum Research Fund36108-AC6
Alfred P. Sloan FoundationUNSPECIFIED
Issue or Number:36
Record Number:CaltechAUTHORS:20170515-143505122
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Official Citation:Transient Absorption Spectroscopy of Ruthenium and Osmium Polypyridyl Complexes Adsorbed onto Nanocrystalline TiO2 Photoelectrodes Darius Kuciauskas, Jeremy E. Monat, Randy Villahermosa, Harry B. Gray, Nathan S. Lewis, and James K. McCusker The Journal of Physical Chemistry B 2002 106 (36), 9347-9358 DOI: 10.1021/jp014589f
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:77464
Deposited By: Tony Diaz
Deposited On:16 May 2017 03:38
Last Modified:15 Nov 2021 17:31

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