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Zigler DF, Morseth ZA, Wang L, et al. Disentangling the Physical Processes Responsible for the Kinetic Complexity in Interfacial Electron Transfer of Excited Ru(II) Polypyridyl Dyes on TiO2. J Am Chem Soc. 2016;138(13):4426-38doi: 10.1021/jacs.5b12996.
Zigler, D. F., Morseth, Z. A., Wang, L., Ashford, D. L., Brennaman, M. K., Grumstrup, E. M., Brigham, E. C., Gish, M. K., Dillon, R. J., Alibabaei, L., Meyer, G. J., Meyer, T. J., & Papanikolas, J. M. (2016). Disentangling the Physical Processes Responsible for the Kinetic Complexity in Interfacial Electron Transfer of Excited Ru(II) Polypyridyl Dyes on TiO2. Journal of the American Chemical Society, 138(13), 4426-38. https://doi.org/10.1021/jacs.5b12996
Zigler, David F, et al. "Disentangling the Physical Processes Responsible for the Kinetic Complexity in Interfacial Electron Transfer of Excited Ru(II) Polypyridyl Dyes on TiO2." Journal of the American Chemical Society vol. 138,13 (2016): 4426-38. doi: https://doi.org/10.1021/jacs.5b12996
Zigler DF, Morseth ZA, Wang L, Ashford DL, Brennaman MK, Grumstrup EM, Brigham EC, Gish MK, Dillon RJ, Alibabaei L, Meyer GJ, Meyer TJ, Papanikolas JM. Disentangling the Physical Processes Responsible for the Kinetic Complexity in Interfacial Electron Transfer of Excited Ru(II) Polypyridyl Dyes on TiO2. J Am Chem Soc. 2016 Apr 06;138(13):4426-38. doi: 10.1021/jacs.5b12996. Epub 2016 Mar 25. PMID: 26974040.
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J Am Chem Soc. 2016 Apr 06;138(13):4426-38. doi: 10.1021/jacs.5b12996. Epub 2016 Mar 25.

Disentangling the Physical Processes Responsible for the Kinetic Complexity in Interfacial Electron Transfer of Excited Ru(II) Polypyridyl Dyes on TiO2.

Journal of the American Chemical Society

David F Zigler, Zachary A Morseth, Li Wang, Dennis L Ashford, M Kyle Brennaman, Erik M Grumstrup, Erinn C Brigham, Melissa K Gish, Robert J Dillon, Leila Alibabaei, Gerald J Meyer, Thomas J Meyer, John M Papanikolas

Affiliations

  1. Caudill, Kenan, and Murray Laboratories, Department of Chemistry, University of North Carolina at Chapel Hill , Campus Box 3290, Chapel Hill, North Carolina 27599, United States.

PMID: 26974040 DOI: 10.1021/jacs.5b12996

Abstract

Interfacial electron transfer at titanium dioxide (TiO2) is investigated for a series of surface bound ruthenium-polypyridyl dyes whose metal-to-ligand charge-transfer state (MLCT) energetics are tuned through chemical modification. The 12 complexes are of the form Ru(II)(bpy-A)(L)2(2+), where bpy-A is a bipyridine ligand functionalized with phosphonate groups for surface attachment to TiO2. Functionalization of ancillary bipyridine ligands (L) enables the potential of the excited state Ru(III/)* couple, E(+/)*, in 0.1 M perchloric acid (HClO4(aq)) to be tuned from -0.69 to -1.03 V vs NHE. Each dye is excited by a 200 fs pulse of light in the visible region of the spectrum and probed with a time-delayed supercontiuum pulse (350-800 nm). Decay of the MLCT excited-state absorption at 376 nm is observed without loss of the ground-state bleach, which is a clear signature of electron injection and formation of the oxidized dye. The dye-dependent decays are biphasic with time constants in the 3-30 and 30-500 ps range. The slower injection rate constant for each dye is exponentially distributed relative to E(+/)*. The correlation between the exponentially diminishing density of TiO2 sub-band acceptor levels and injection rate is well described using Marcus-Gerischer theory, with the slower decay components being assigned to injection from the thermally equilibrated state and the faster components corresponding to injection from higher energy states within the (3)MLCT manifold. These results and detailed analyses incorporating molecular photophysics and semiconductor density of states measurements indicate that the multiexponential behavior that is often observed in interfacial injection studies is not due to sample heterogeneity. Rather, this work shows that the kinetic heterogeneity results from competition between excited-state relaxation and injection as the photoexcited dye relaxes through the (3)MLCT manifold to the thermally equilibrated state, underscoring the potential for a simple kinetic model to reproduce the complex kinetic behavior often observed at the interface of mesoporous metal oxide materials.

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