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Theoretical study of catalytic mechanism for single-site water oxidation process.

Publication ,  Journal Article
Lin, X; Hu, X; Concepcion, JJ; Chen, Z; Liu, S; Meyer, TJ; Yang, W
Published in: Proceedings of the National Academy of Sciences of the United States of America
September 2012

Water oxidation is a linchpin in solar fuels formation, and catalysis by single-site ruthenium complexes has generated significant interest in this area. Combining several theoretical tools, we have studied the entire catalytic cycle of water oxidation for a single-site catalyst starting with [Ru(II)(tpy)(bpm)(OH(2))](2+) (i.e., [Ru(II)-OH(2)](2+); tpy is 2,2':6',2''-terpyridine and bpm is 2,2'-bypyrimidine) as a representative example of a new class of single-site catalysts. The redox potentials and pK(a) calculations for the first two proton-coupled electron transfers (PCETs) from [Ru(II)-OH(2)](2+) to [Ru(IV) = O](2+) and the following electron-transfer process to [Ru(V) = O](3+) suggest that these processes can proceed readily in acidic or weakly basic conditions. The subsequent water splitting process involves two water molecules, [Ru(V) = O](3+) to generate [Ru(III)-OOH](2+), and H(3)O(+) with a low activation barrier (~10 kcal/mol). After the key O-O bond forming step in the single-site Ru catalysis, another PECT process oxidizes [Ru(III)-OOH](2+) to [Ru(IV)-OO](2+) when the pH is lower than 3.7. Two possible forms of [Ru(IV)-OO](2+), open and closed, can exist and interconvert with a low activation barrier (< 7 kcal/mol) due to strong spin-orbital coupling effects. In Pathway 1 at pH = 1.0, oxygen release is rate-limiting with an activation barrier ~12 kcal/mol while the electron-transfer step from [Ru(IV)-OO](2+) to [Ru(V)-OO](3+) becomes rate-determining at pH = 0 (Pathway 2) with Ce(IV) as oxidant. The results of these theoretical studies with atomistic details have revealed subtle details of reaction mechanisms at several stages during the catalytic cycle. This understanding is helpful in the design of new catalysts for water oxidation.

Duke Scholars

Published In

Proceedings of the National Academy of Sciences of the United States of America

DOI

EISSN

1091-6490

ISSN

0027-8424

Publication Date

September 2012

Volume

109

Issue

39

Start / End Page

15669 / 15672

Related Subject Headings

  • Water
  • Ruthenium
  • Photochemical Processes
  • Oxidation-Reduction
  • Organometallic Compounds
  • Models, Chemical
  • Catalysis
 

Citation

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Lin, X., Hu, X., Concepcion, J. J., Chen, Z., Liu, S., Meyer, T. J., & Yang, W. (2012). Theoretical study of catalytic mechanism for single-site water oxidation process. Proceedings of the National Academy of Sciences of the United States of America, 109(39), 15669–15672. https://doi.org/10.1073/pnas.1118344109
Lin, Xiangsong, Xiangqian Hu, Javier J. Concepcion, Zuofeng Chen, Shubin Liu, Thomas J. Meyer, and Weitao Yang. “Theoretical study of catalytic mechanism for single-site water oxidation process.Proceedings of the National Academy of Sciences of the United States of America 109, no. 39 (September 2012): 15669–72. https://doi.org/10.1073/pnas.1118344109.
Lin X, Hu X, Concepcion JJ, Chen Z, Liu S, Meyer TJ, et al. Theoretical study of catalytic mechanism for single-site water oxidation process. Proceedings of the National Academy of Sciences of the United States of America. 2012 Sep;109(39):15669–72.
Lin, Xiangsong, et al. “Theoretical study of catalytic mechanism for single-site water oxidation process.Proceedings of the National Academy of Sciences of the United States of America, vol. 109, no. 39, Sept. 2012, pp. 15669–72. Epmc, doi:10.1073/pnas.1118344109.
Lin X, Hu X, Concepcion JJ, Chen Z, Liu S, Meyer TJ, Yang W. Theoretical study of catalytic mechanism for single-site water oxidation process. Proceedings of the National Academy of Sciences of the United States of America. 2012 Sep;109(39):15669–15672.
Journal cover image

Published In

Proceedings of the National Academy of Sciences of the United States of America

DOI

EISSN

1091-6490

ISSN

0027-8424

Publication Date

September 2012

Volume

109

Issue

39

Start / End Page

15669 / 15672

Related Subject Headings

  • Water
  • Ruthenium
  • Photochemical Processes
  • Oxidation-Reduction
  • Organometallic Compounds
  • Models, Chemical
  • Catalysis