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Comparison of the Self-Exchange and Interfacial Charge-Transfer Rate Constants for Methyl- versustert-Butyl-Substituted Os(III) Polypyridyl Complexes

Hamann, Thomas W. and Brunschwig, Bruce S. and Lewis, Nathan S. (2006) Comparison of the Self-Exchange and Interfacial Charge-Transfer Rate Constants for Methyl- versustert-Butyl-Substituted Os(III) Polypyridyl Complexes. Journal of Physical Chemistry B, 110 (50). pp. 25514-25520. ISSN 1520-6106. https://resolver.caltech.edu/CaltechAUTHORS:20170712-070026392

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Abstract

Differences in the self-exchange and interfacial electron-transfer rate constants have been evaluated for a relatively unhindered Os(III/II) redox system, osmium(III/II) tris(4,4‘-di-methyl-2,2‘-bipyridyl), [Os(Me_2bpy)_3]^(3+/2+), relative to those of a relatively hindered system, osmium(III/II) tris(4,4‘-di-tert-butyl-2,2‘-bipyridyl), [Os(t-Bu_2bpy)_3]^(3+/2+). In contrast to the predicted increase in rate constant by a factor of 2−3 due to the difference in reorganization energy of the two complexes, introduction of the tert-butyl functionality decreased the self-exchange rate constant, as measured by NMR line-broadening techniques, by a factor of ∼50 as compared to that of the analogous methyl-substituted osmium complex. Steady-state current density versus potential measurements, in conjunction with differential capacitance versus potential measurements, were used to compare the interfacial electron-transfer rate constants at n-type ZnO electrodes of [Os(t-Bu_2bpy)_3]^(3+/2+) and [Os(Me_2bpy)_3]^(3+/2+). The interfacial electron-transfer rate constant for the reduction of [Os(t-Bu_2bpy)_3]^(3+) was 100 times smaller than that for [Os(Me_2bpy)_3]^(3+). The results indicate that the tert-butyl group can act as a spacer on an outer-sphere redox couple and significantly decrease the electronic coupling of the electron-transfer reaction in both self-exchange and interfacial electron-transfer processes.


Item Type:Article
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URLURL TypeDescription
http://dx.doi.org/10.1021/jp0649697DOIArticle
http://pubs.acs.org/doi/abs/10.1021/jp0649697PublisherArticle
ORCID:
AuthorORCID
Brunschwig, Bruce S.0000-0002-6135-6727
Lewis, Nathan S.0000-0001-5245-0538
Additional Information:© 2006 American Chemical Society. Received 2 August 2006. Published online 14 December 2006. Published in print 1 December 2006. We thank Dr. Norman Sutin for very helpful discussions. We thank the Office of Basic Energy Sciences, Department of Energy, for support of this work, and acknowledge support from the Molecular Materials Resource Center of the Beckman Institute at the California Institute of Technology.
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Department of Energy (DOE)UNSPECIFIED
Caltech Beckman InstituteUNSPECIFIED
Issue or Number:50
Record Number:CaltechAUTHORS:20170712-070026392
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20170712-070026392
Official Citation:Comparison of the Self-Exchange and Interfacial Charge-Transfer Rate Constants for Methyl- versus tert-Butyl-Substituted Os(III) Polypyridyl Complexes Thomas W. Hamann, Bruce S. Brunschwig, and Nathan S. Lewis The Journal of Physical Chemistry B 2006 110 (50), 25514-25520 DOI: 10.1021/jp0649697
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:78977
Collection:CaltechAUTHORS
Deposited By: Ruth Sustaita
Deposited On:12 Jul 2017 18:04
Last Modified:03 Oct 2019 18:14

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