skip to main content
DOE PAGES title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: O–O Radical Coupling: From Detailed Mechanistic Understanding to Enhanced Water Oxidation Catalysis

Abstract

In this paper, a deeper mechanistic understanding of the key O–O bond formation step of water oxidation by the [Ru(bda)(L)2] (bdaH2 = 2,2'-bipyridine-6,6'-dicarboxylic acid; L is a pyridine or isoquinoline derivative) family of catalysts is reached through harmonious experimental and computational studies of two series of modified catalysts with systematic variations in the axial ligands. The introduction of halogen and electron-donating substituents in [Ru(bda)(4-X-py)2] and [Ru(bda)(6-X-isq)2] (X is H, Cl, Br, and I for the pyridine series and H, F, Cl, Br, and OMe for the isoquinoline series) enhances the noncovalent interactions between the axial ligands in the transition state for the bimolecular O–O coupling, resulting in a lower activation barrier and faster catalysis. From detailed transition state calculations in combination with experimental kinetic studies, we find that the main contributor to the free energy of activation is entropy due to the highly organized transition states, which is contrary to other reports. Previous work has considered only the electronic influence of the substituents, suggesting electron-withdrawing groups accelerate catalysis, but we show that a balance between polarizability and favorable π–π interactions is the key, leading to rationally devised improvements. Our calculations predict the catalysts with the lowest ΔG for the O–Omore » coupling step to be [Ru(bda)(4-I-py)2] and [Ru(bda)(6,7-(OMe)2-isq)2] for the pyridine and isoquinoline families, respectively. Our experimental results corroborate these predictions: the turnover frequency for [Ru(bda)(4-I-py)2] (330 s–1) is a 10-fold enhancement with respect to that of [Ru(bda)(py)2], and the turnover frequency for [Ru(bda)(6-OMe-isq)2] reaches 1270 s–1, two times faster than [Ru(bda)(isq)2].« less

Authors:
ORCiD logo [1]; ORCiD logo [1]; ORCiD logo [1]
  1. Chemistry Division, Brookhaven National Laboratory, Upton, New York 11973, United States
Publication Date:
Research Org.:
Brookhaven National Lab. (BNL), Upton, NY (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES). Chemical Sciences, Geosciences, and Biosciences Division
OSTI Identifier:
1435374
Alternate Identifier(s):
OSTI ID: 1476288
Report Number(s):
BNL-209120-2018-JAAM
Journal ID: ISSN 0020-1669
Grant/Contract Number:  
SC00112704; SC0012704
Resource Type:
Published Article
Journal Name:
Inorganic Chemistry
Additional Journal Information:
Journal Name: Inorganic Chemistry Journal Volume: 57 Journal Issue: 17; Journal ID: ISSN 0020-1669
Publisher:
American Chemical Society (ACS)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; water oxidation; ruthenium catalysts; halogen substituents; DFT calculations; stopped-flow kinetics; kinetic/mechanistic studies

Citation Formats

Xie, Yan, Shaffer, David W., and Concepcion, Javier J. O–O Radical Coupling: From Detailed Mechanistic Understanding to Enhanced Water Oxidation Catalysis. United States: N. p., 2018. Web. https://doi.org/10.1021/acs.inorgchem.8b00329.
Xie, Yan, Shaffer, David W., & Concepcion, Javier J. O–O Radical Coupling: From Detailed Mechanistic Understanding to Enhanced Water Oxidation Catalysis. United States. https://doi.org/10.1021/acs.inorgchem.8b00329
Xie, Yan, Shaffer, David W., and Concepcion, Javier J. Mon . "O–O Radical Coupling: From Detailed Mechanistic Understanding to Enhanced Water Oxidation Catalysis". United States. https://doi.org/10.1021/acs.inorgchem.8b00329.
@article{osti_1435374,
title = {O–O Radical Coupling: From Detailed Mechanistic Understanding to Enhanced Water Oxidation Catalysis},
author = {Xie, Yan and Shaffer, David W. and Concepcion, Javier J.},
abstractNote = {In this paper, a deeper mechanistic understanding of the key O–O bond formation step of water oxidation by the [Ru(bda)(L)2] (bdaH2 = 2,2'-bipyridine-6,6'-dicarboxylic acid; L is a pyridine or isoquinoline derivative) family of catalysts is reached through harmonious experimental and computational studies of two series of modified catalysts with systematic variations in the axial ligands. The introduction of halogen and electron-donating substituents in [Ru(bda)(4-X-py)2] and [Ru(bda)(6-X-isq)2] (X is H, Cl, Br, and I for the pyridine series and H, F, Cl, Br, and OMe for the isoquinoline series) enhances the noncovalent interactions between the axial ligands in the transition state for the bimolecular O–O coupling, resulting in a lower activation barrier and faster catalysis. From detailed transition state calculations in combination with experimental kinetic studies, we find that the main contributor to the free energy of activation is entropy due to the highly organized transition states, which is contrary to other reports. Previous work has considered only the electronic influence of the substituents, suggesting electron-withdrawing groups accelerate catalysis, but we show that a balance between polarizability and favorable π–π interactions is the key, leading to rationally devised improvements. Our calculations predict the catalysts with the lowest ΔG‡ for the O–O coupling step to be [Ru(bda)(4-I-py)2] and [Ru(bda)(6,7-(OMe)2-isq)2] for the pyridine and isoquinoline families, respectively. Our experimental results corroborate these predictions: the turnover frequency for [Ru(bda)(4-I-py)2] (330 s–1) is a 10-fold enhancement with respect to that of [Ru(bda)(py)2], and the turnover frequency for [Ru(bda)(6-OMe-isq)2] reaches 1270 s–1, two times faster than [Ru(bda)(isq)2].},
doi = {10.1021/acs.inorgchem.8b00329},
journal = {Inorganic Chemistry},
number = 17,
volume = 57,
place = {United States},
year = {2018},
month = {4}
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record
https://doi.org/10.1021/acs.inorgchem.8b00329

Citation Metrics:
Cited by: 9 works
Citation information provided by
Web of Science

Save / Share:

Works referencing / citing this record:

Impact of substituents on molecular properties and catalytic activities of trinuclear Ru macrocycles in water oxidation
journal, January 2020

  • Meza-Chincha, Ana-Lucia; Lindner, Joachim O.; Schindler, Dorothee
  • Chemical Science
  • DOI: 10.1039/d0sc01097a

Iridium Water Oxidation Catalysts Based on Pyridine‐Carbene Alkyl‐Substituted Ligands
journal, March 2019

  • Corbucci, Ilaria; Zaccaria, Francesco; Heath, Rachel
  • ChemCatChem, Vol. 11, Issue 21
  • DOI: 10.1002/cctc.201901092

Catalytic Oxidation of Water to Dioxygen by Mononuclear Ru Complexes Bearing a 2,6‐Pyridinedicarboxylato Ligand
journal, November 2018

  • Hoque, Md Asmaul; Benet‐Buchholz, Jordi; Llobet, Antoni
  • ChemSusChem, Vol. 12, Issue 9
  • DOI: 10.1002/cssc.201802996

The Art of Splitting Water: Storing Energy in a Readily Available and Convenient Form: The Art of Splitting Water: Storing Energy in a Readily Available and Convenient Form
journal, March 2019

  • Shatskiy, Andrey; Kärkäs, Markus D.; Åkermark, Björn
  • European Journal of Inorganic Chemistry, Vol. 2019, Issue 15
  • DOI: 10.1002/ejic.201801548

The development of molecular water oxidation catalysts
journal, April 2019

  • Matheu, Roc; Garrido-Barros, Pablo; Gil-Sepulcre, Marcos
  • Nature Reviews Chemistry, Vol. 3, Issue 5
  • DOI: 10.1038/s41570-019-0096-0

Artificial photosynthesis: opportunities and challenges of molecular catalysts
journal, January 2019

  • Zhang, Biaobiao; Sun, Licheng
  • Chemical Society Reviews, Vol. 48, Issue 7
  • DOI: 10.1039/c8cs00897c

Kinetics and mechanisms of catalytic water oxidation
journal, January 2019

  • Fukuzumi, Shunichi; Lee, Yong-Min; Nam, Wonwoo
  • Dalton Transactions, Vol. 48, Issue 3
  • DOI: 10.1039/c8dt04341h

Early photophysical events of a ruthenium( ii ) molecular dyad capable of performing photochemical water oxidation and of its model compounds
journal, January 2019

  • Nastasi, Francesco; Santoro, Antonio; Serroni, Scolastica
  • Photochemical & Photobiological Sciences, Vol. 18, Issue 9
  • DOI: 10.1039/c8pp00530c

A stable dye-sensitized photoelectrosynthesis cell mediated by a NiO overlayer for water oxidation
journal, September 2019

  • Wang, Degao; Niu, Fujun; Mortelliti, Michael J.
  • Proceedings of the National Academy of Sciences, Vol. 117, Issue 23
  • DOI: 10.1073/pnas.1821687116

Modeling the Catalyst Activation Step in a Metal–Ligand Radical Mechanism Based Water Oxidation System
journal, May 2019