Water oxidation by a ruthenium complex with noninnocent quinone ligands

Possible formation of an O-O bond at a low oxidation state of the metal

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164 Citations (Scopus)

Abstract

Tanaka and co-workers reported a novel dinuclear Ru complex, [Ru 2(OH)2(3,6-Bu2Q)2(btpyan)](SbF 6)2 (3,6-Bu2Q = 3,6-ditert-butyl-1,2- benzoquinone, btpyan = 1,8-bis(2,2′:6′,2″-terpyrid-4′- yl)anthracene), that contains redox active quinone ligands and has an excellent electrocatalytic activity for water oxidation when immobilized on an indium-tin-oxide electrode (Inorg. Chem., 2001, 40, 329-337). The novel features of the dinuclear and related mononuclear Ru species with quinone ligands, and comparison of their properties to those of the Ru analogues with the bpy ligand (bpy = 2,2′-bipyridine) replacing quinone, are summarized here together with new theoretical and experimental results that show striking features for both the dinuclear and mononuclear species. The identity and oxidation state of key mononuclear species, including the previously reported oxyl radical, have been reassigned. Our gas-phase theoretical calculations indicate that the Tanaka Ru-dinuclear catalyst seems to maintain predominantly Ru(II) centers while the quinone ligands and water moiety are involved in redox reactions throughout the entire catalytic cycle for water oxidation. Our theoretical study identifies [Ru2(O2 -)(Q-1.5)2(btpyan) ]0 as a key intermediate and the most reduced catalyst species that is formed by removal of all four protons before four-electron oxidation takes place. While our study toward understanding the complicated electronic and geometric structures of possible intermediates in the catalytic cycle is still in progress, the current status and new directions for kinetic and mechanistic investigations, and key issues and challenges in water oxidation with the Tanaka catalyst (and its analogues with Cl- or NO2-substituted quinones and a species with a xanthene bridge instead an antheracene) are discussed.

Original languageEnglish
Pages (from-to)1787-1802
Number of pages16
JournalInorganic Chemistry
Volume47
Issue number6
DOIs
Publication statusPublished - Mar 17 2008

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Ruthenium
quinones
ruthenium
Metals
Ligands
Oxidation
ligands
oxidation
Water
metals
water
Catalysts
catalysts
Xanthenes
Quinones
analogs
Redox reactions
cycles
Protons
anthracene

ASJC Scopus subject areas

  • Inorganic Chemistry

Cite this

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title = "Water oxidation by a ruthenium complex with noninnocent quinone ligands: Possible formation of an O-O bond at a low oxidation state of the metal",
abstract = "Tanaka and co-workers reported a novel dinuclear Ru complex, [Ru 2(OH)2(3,6-Bu2Q)2(btpyan)](SbF 6)2 (3,6-Bu2Q = 3,6-ditert-butyl-1,2- benzoquinone, btpyan = 1,8-bis(2,2′:6′,2″-terpyrid-4′- yl)anthracene), that contains redox active quinone ligands and has an excellent electrocatalytic activity for water oxidation when immobilized on an indium-tin-oxide electrode (Inorg. Chem., 2001, 40, 329-337). The novel features of the dinuclear and related mononuclear Ru species with quinone ligands, and comparison of their properties to those of the Ru analogues with the bpy ligand (bpy = 2,2′-bipyridine) replacing quinone, are summarized here together with new theoretical and experimental results that show striking features for both the dinuclear and mononuclear species. The identity and oxidation state of key mononuclear species, including the previously reported oxyl radical, have been reassigned. Our gas-phase theoretical calculations indicate that the Tanaka Ru-dinuclear catalyst seems to maintain predominantly Ru(II) centers while the quinone ligands and water moiety are involved in redox reactions throughout the entire catalytic cycle for water oxidation. Our theoretical study identifies [Ru2(O2 -)(Q-1.5)2(btpyan) ]0 as a key intermediate and the most reduced catalyst species that is formed by removal of all four protons before four-electron oxidation takes place. While our study toward understanding the complicated electronic and geometric structures of possible intermediates in the catalytic cycle is still in progress, the current status and new directions for kinetic and mechanistic investigations, and key issues and challenges in water oxidation with the Tanaka catalyst (and its analogues with Cl- or NO2-substituted quinones and a species with a xanthene bridge instead an antheracene) are discussed.",
author = "James Muckerman and Dmitry Polyansky and Tohru Wada and Koji Tanaka and Etsuko Fujita",
year = "2008",
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T1 - Water oxidation by a ruthenium complex with noninnocent quinone ligands

T2 - Possible formation of an O-O bond at a low oxidation state of the metal

AU - Muckerman, James

AU - Polyansky, Dmitry

AU - Wada, Tohru

AU - Tanaka, Koji

AU - Fujita, Etsuko

PY - 2008/3/17

Y1 - 2008/3/17

N2 - Tanaka and co-workers reported a novel dinuclear Ru complex, [Ru 2(OH)2(3,6-Bu2Q)2(btpyan)](SbF 6)2 (3,6-Bu2Q = 3,6-ditert-butyl-1,2- benzoquinone, btpyan = 1,8-bis(2,2′:6′,2″-terpyrid-4′- yl)anthracene), that contains redox active quinone ligands and has an excellent electrocatalytic activity for water oxidation when immobilized on an indium-tin-oxide electrode (Inorg. Chem., 2001, 40, 329-337). The novel features of the dinuclear and related mononuclear Ru species with quinone ligands, and comparison of their properties to those of the Ru analogues with the bpy ligand (bpy = 2,2′-bipyridine) replacing quinone, are summarized here together with new theoretical and experimental results that show striking features for both the dinuclear and mononuclear species. The identity and oxidation state of key mononuclear species, including the previously reported oxyl radical, have been reassigned. Our gas-phase theoretical calculations indicate that the Tanaka Ru-dinuclear catalyst seems to maintain predominantly Ru(II) centers while the quinone ligands and water moiety are involved in redox reactions throughout the entire catalytic cycle for water oxidation. Our theoretical study identifies [Ru2(O2 -)(Q-1.5)2(btpyan) ]0 as a key intermediate and the most reduced catalyst species that is formed by removal of all four protons before four-electron oxidation takes place. While our study toward understanding the complicated electronic and geometric structures of possible intermediates in the catalytic cycle is still in progress, the current status and new directions for kinetic and mechanistic investigations, and key issues and challenges in water oxidation with the Tanaka catalyst (and its analogues with Cl- or NO2-substituted quinones and a species with a xanthene bridge instead an antheracene) are discussed.

AB - Tanaka and co-workers reported a novel dinuclear Ru complex, [Ru 2(OH)2(3,6-Bu2Q)2(btpyan)](SbF 6)2 (3,6-Bu2Q = 3,6-ditert-butyl-1,2- benzoquinone, btpyan = 1,8-bis(2,2′:6′,2″-terpyrid-4′- yl)anthracene), that contains redox active quinone ligands and has an excellent electrocatalytic activity for water oxidation when immobilized on an indium-tin-oxide electrode (Inorg. Chem., 2001, 40, 329-337). The novel features of the dinuclear and related mononuclear Ru species with quinone ligands, and comparison of their properties to those of the Ru analogues with the bpy ligand (bpy = 2,2′-bipyridine) replacing quinone, are summarized here together with new theoretical and experimental results that show striking features for both the dinuclear and mononuclear species. The identity and oxidation state of key mononuclear species, including the previously reported oxyl radical, have been reassigned. Our gas-phase theoretical calculations indicate that the Tanaka Ru-dinuclear catalyst seems to maintain predominantly Ru(II) centers while the quinone ligands and water moiety are involved in redox reactions throughout the entire catalytic cycle for water oxidation. Our theoretical study identifies [Ru2(O2 -)(Q-1.5)2(btpyan) ]0 as a key intermediate and the most reduced catalyst species that is formed by removal of all four protons before four-electron oxidation takes place. While our study toward understanding the complicated electronic and geometric structures of possible intermediates in the catalytic cycle is still in progress, the current status and new directions for kinetic and mechanistic investigations, and key issues and challenges in water oxidation with the Tanaka catalyst (and its analogues with Cl- or NO2-substituted quinones and a species with a xanthene bridge instead an antheracene) are discussed.

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