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Title: Mechanistic analysis of water oxidation catalyst cis-[Ru(bpy) 2(H 2O) 2] 2+: Effect of dimerization

While the catalytic activity of some Ru-based polypyridine complexes in water oxidation is well established, the relationship between their chemical structure and activity is less known. In this work, the single site Ru complex [Ru(bpy) 2(H 2O) 2] 2+ (bpy = 2,20-bipyridine)—which can exist as either a cis isomer or a trans isomer—is investigated. While a difference in the catalytic activity of these two isomers is well established, with cis-[Ru(bpy) 2(H 2O) 2] 2+ being much more active, no mechanistic explanation of this fact has been presented. The oxygen evolving capability of both isomers at multiple concentrations has been investigated, with cis-[Ru(bpy) 2(H 2O) 2] 2+ showing a second-order dependence of O2 evolution activity with increased catalyst concentration. Measurement of the electron paramagnetic resonance (EPR) spectrum of cis-[Ru(bpy) 2(H 2O) 2] 2+, shortly after oxidation with CeIV, showed the presence of a signal matching that of cis,cis-[Ru III(bpy) 2(H 2O)ORu IV(bpy) 2(OH)] 4+, also known as “blue dimer”. The formation of dimers is a concentration-dependent process, which could serve to explain the greater than first order increase in catalytic activity. The trans isomer showed a first-order dependence of O 2 evolution on catalyst concentration. As a result, behavior of [Ru(bpy)more » 2(H 2O) 2] 2+ isomers is compared with other Ru-based catalysts, in particular [Ru(tpy)(bpy)(H 2O)] 2+ (tpy = 2,20;6,20 0-terpyridine).« less
Authors:
 [1] ;  [1] ;  [1]
  1. Purdue Univ., West Lafayette, IN (United States)
Publication Date:
Grant/Contract Number:
SC0009988
Type:
Accepted Manuscript
Journal Name:
Catalysts
Additional Journal Information:
Journal Volume: 7; Journal Issue: 2; Journal ID: ISSN 2073-4344
Publisher:
MDPI
Research Org:
Purdue Univ., West Lafayette, IN (United States)
Sponsoring Org:
USDOE Office of Science (SC)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; Ru complexes; catalysis of water oxidation; density functional theory; X-ban EPR spectroscopy; oxygen evolution; H-bond; dimer formation
OSTI Identifier:
1358441

Erdman, Darren, Pineda-Galvan, Yuliana, and Pushkar, Yulia. Mechanistic analysis of water oxidation catalyst cis-[Ru(bpy)2(H2O)2]2+: Effect of dimerization. United States: N. p., Web. doi:10.3390/catal7020039.
Erdman, Darren, Pineda-Galvan, Yuliana, & Pushkar, Yulia. Mechanistic analysis of water oxidation catalyst cis-[Ru(bpy)2(H2O)2]2+: Effect of dimerization. United States. doi:10.3390/catal7020039.
Erdman, Darren, Pineda-Galvan, Yuliana, and Pushkar, Yulia. 2017. "Mechanistic analysis of water oxidation catalyst cis-[Ru(bpy)2(H2O)2]2+: Effect of dimerization". United States. doi:10.3390/catal7020039. https://www.osti.gov/servlets/purl/1358441.
@article{osti_1358441,
title = {Mechanistic analysis of water oxidation catalyst cis-[Ru(bpy)2(H2O)2]2+: Effect of dimerization},
author = {Erdman, Darren and Pineda-Galvan, Yuliana and Pushkar, Yulia},
abstractNote = {While the catalytic activity of some Ru-based polypyridine complexes in water oxidation is well established, the relationship between their chemical structure and activity is less known. In this work, the single site Ru complex [Ru(bpy)2(H2O)2]2+ (bpy = 2,20-bipyridine)—which can exist as either a cis isomer or a trans isomer—is investigated. While a difference in the catalytic activity of these two isomers is well established, with cis-[Ru(bpy)2(H2O)2]2+ being much more active, no mechanistic explanation of this fact has been presented. The oxygen evolving capability of both isomers at multiple concentrations has been investigated, with cis-[Ru(bpy)2(H2O)2]2+ showing a second-order dependence of O2 evolution activity with increased catalyst concentration. Measurement of the electron paramagnetic resonance (EPR) spectrum of cis-[Ru(bpy)2(H2O)2]2+, shortly after oxidation with CeIV, showed the presence of a signal matching that of cis,cis-[RuIII(bpy)2(H2O)ORuIV(bpy)2(OH)]4+, also known as “blue dimer”. The formation of dimers is a concentration-dependent process, which could serve to explain the greater than first order increase in catalytic activity. The trans isomer showed a first-order dependence of O2 evolution on catalyst concentration. As a result, behavior of [Ru(bpy)2(H2O)2]2+ isomers is compared with other Ru-based catalysts, in particular [Ru(tpy)(bpy)(H2O)]2+ (tpy = 2,20;6,20 0-terpyridine).},
doi = {10.3390/catal7020039},
journal = {Catalysts},
number = 2,
volume = 7,
place = {United States},
year = {2017},
month = {1}
}