Title: The Role of Seven-Coordination in Ru-Catalyzed Water Oxidation

Abstract

A family of Ru complexes based on the pentadentate ligand t5a^3– ((2,5-bis(6-carboxylatopyridin-2-yl)pyrrol-1-ide) and pyridine (py) that includes {Ru^II(Ht5a-κ-N²O)(py)₃} (1H^II(κ-N²O)), {Ru^III(t5a-κ-N³O^1.5)(py)₂} (2^III(κ-N³O^1.5)), and {Ru^IV(t5a-κ-N³O²)(py)₂}+ ({2^IV(κ-N3O²)}+) has been prepared and thoroughly characterized. Complexes 1HII(κ-N²O), 2^III(κ-N³O^1.5), and {2^IV(κ-N³O²)}+ have been investigated in solution by spectroscopic methods (NMR, UV–vis) and in the solid state by single-crystal X-ray diffraction analysis and complemented by density functional theory (DFT) calculations. The redox properties of complex 2^III(κ-N³O^1.5) have been studied by electrochemical methods (CV and DPV), showing its easy access to high oxidation states, thanks to the trianionic nature of the t5a^3– ligand. Under neutral to basic conditions complex {2^IV(κ-N3O²)}+ undergoes aquation, generating {Ru^IV(OH)(t5a-κ-N²O)(py)₂} (2^IV(OH)(κ-N²O)). Further oxidation of the complex forms {Ru^V(O)(t5a-κ-N²O)(py)₂} (2^V(O)(κ-N²O)), which is a very efficient water oxidation catalyst, reaching a TOF_MAX value of 9400 s^–1 at pH 7.0, as measured via foot of the wave analysis. The key to fast kinetics for the catalytic oxidation of water to dioxygen by 2^V(O)(κ-N²O) is due not only to the easy access to high oxidation states but also to the intramolecular hydrogen bonding provided by the noncoordinated dangling carboxylate at the transition state, as corroborated by DFT calculations.

Authors:

Matheu, Roc  ^[1];

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• Search DOE PAGES for ORCID "0000-0001-8601-5219"

Ertem, Mehmed Z. ^[2]; Pipelier, Muriel ^[3]; Lebreton, Jacques  ^[3];

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• Search DOE PAGES for ORCID "0000-0003-2603-8982"

Dubreuil, Didier ^[3]; Benet-Buchholz, Jordi ^[4]; Sala, Xavier ^[5]; Tessier, Arnaud ^[3]; Llobet, Antoni  ^[6]

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• Search DOE PAGES for ORCID "0000-0002-6176-5272"

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1. The Barcelona Institute of Science and Technology (BIST), Tarragona (Spain). Inst. of Chemical Research of Catalonia (ICIQ); Univ. Rovira i Virgli, Tarragona (Spain)
2. Brookhaven National Lab. (BNL), Upton, NY (United States)
3. Univ. de Nantes (France)
4. The Barcelona Institute of Science and Technology (BIST), Tarragona (Spain). Inst. of Chemical Research of Catalonia (ICIQ)
5. Univ. Autonoma de Barcelona (Spain)
6. The Barcelona Institute of Science and Technology (BIST), Tarragona (Spain). Inst. of Chemical Research of Catalonia (ICIQ); Univ. Autonoma de Barcelona (Spain)

Publication Date:

Fri Jan 19 00:00:00 EST 2018

Research Org.:

Brookhaven National Lab. (BNL), Upton, NY (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Basic Energy Sciences (BES)

OSTI Identifier:

1425070

Report Number(s):

BNL-203210-2018-JAAM
Journal ID: ISSN 2155-5435

Grant/Contract Number:  

SC0012704

Resource Type:

Accepted Manuscript

Journal Name:

ACS Catalysis

Additional Journal Information:

Journal Volume: 8; Journal Issue: 3; Journal ID: ISSN 2155-5435

Publisher:

American Chemical Society (ACS)

Country of Publication:

United States

Language:

English

Subject:

37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY