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Title: Hydrogen Bonding Rescues Overpotential in Seven-Coordinated Ru Water Oxidation Catalysts

Abstract

In this paper, we describe the synthesis, structural characterization, and redox properties of two new Ru complexes containing the dianionic potentially pentadentate [2,2':6',2"-terpyridine]-6,6"-dicarboxylate (tda 2–) ligand that coordinates Ru at the equatorial plane and with additional pyridine or dmso acting as monondentate ligand in the axial positions: [Ru II(tda-κ-N 3O)(py)(dmso)], 1 II and [Ru III(tda-κ-N 3O 2)(py)(H 2O) ax] +, 2 III(H 2O) +. Complex 1 II has been characterized by single-crystal XRD in the solid state and in solution by NMR spectroscopy. The redox properties of 1 II and 2 III(H 2O) + have been thoroughly investigated by means of cyclic voltammetry and differential pulse voltammetry. Complex 2 II(H 2O) displays poor catalytic activity with regard to the oxidation of water to dioxygen, and its properties have been analyzed on the basis of foot of the wave analysis and catalytic Tafel plots. The activity of 2 II(H 2O) has been compared with related water oxidation catalysts (WOCs) previously described in the literature. Despite its moderate activity, 2 II(H 2O) constitutes the cornerstone that has triggered the rationalization of the different factors that govern overpotentials as well as efficiencies in molecular WOCs. The present work uncovers the interplay between differentmore » parameters, namely, coordination number, number of anionic groups bonded to the first-coordination sphere of the metal center, water oxidation catalysis overpotential, p K a and hydrogen bonding, and the performance of a given WOC. It thus establishes the basic principles for the design of efficient WOCs operating at low overpotentials.« less

Authors:
ORCiD logo [1];  [2];  [3];  [3];  [4]; ORCiD logo [5]
  1. Barcelona Institute of Science and Technology (BIST), Tarragona (Spain); Univ. Rovira i Virgili, Tarragona (Spain)
  2. Brookhaven National Lab. (BNL), Upton, NY (United States)
  3. Barcelona Institute of Science and Technology (BIST), Tarragona (Spain)
  4. Univ. Autonoma de Barcelona, Barcelona (Spain)
  5. Barcelona Institute of Science and Technology (BIST), Tarragona (Spain); Univ. Autonoma de Barcelona, Barcelona (Spain)
Publication Date:
Research Org.:
Brookhaven National Laboratory (BNL), Upton, NY (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1405933
Report Number(s):
BNL-114431-2017-JA
Journal ID: ISSN 2155-5435; R&D Project: CO026; KC0304030
Grant/Contract Number:
SC0012704
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
ACS Catalysis
Additional Journal Information:
Journal Volume: 7; Journal Issue: 10; 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; electrocatalysis; hydrogen bonding; redox properties; Ru complexes; seven coordination; water oxidation catalysis; water splitting

Citation Formats

Matheu, Roc, Ertem, Mehmed Z., Gimbert-Surinach, Carolina, Benet-Buchholz, Jordi, Sala, Xavier, and Llobet, Antoni. Hydrogen Bonding Rescues Overpotential in Seven-Coordinated Ru Water Oxidation Catalysts. United States: N. p., 2017. Web. doi:10.1021/acscatal.7b01860.
Matheu, Roc, Ertem, Mehmed Z., Gimbert-Surinach, Carolina, Benet-Buchholz, Jordi, Sala, Xavier, & Llobet, Antoni. Hydrogen Bonding Rescues Overpotential in Seven-Coordinated Ru Water Oxidation Catalysts. United States. doi:10.1021/acscatal.7b01860.
Matheu, Roc, Ertem, Mehmed Z., Gimbert-Surinach, Carolina, Benet-Buchholz, Jordi, Sala, Xavier, and Llobet, Antoni. 2017. "Hydrogen Bonding Rescues Overpotential in Seven-Coordinated Ru Water Oxidation Catalysts". United States. doi:10.1021/acscatal.7b01860.
@article{osti_1405933,
title = {Hydrogen Bonding Rescues Overpotential in Seven-Coordinated Ru Water Oxidation Catalysts},
author = {Matheu, Roc and Ertem, Mehmed Z. and Gimbert-Surinach, Carolina and Benet-Buchholz, Jordi and Sala, Xavier and Llobet, Antoni},
abstractNote = {In this paper, we describe the synthesis, structural characterization, and redox properties of two new Ru complexes containing the dianionic potentially pentadentate [2,2':6',2"-terpyridine]-6,6"-dicarboxylate (tda2–) ligand that coordinates Ru at the equatorial plane and with additional pyridine or dmso acting as monondentate ligand in the axial positions: [RuII(tda-κ-N3O)(py)(dmso)], 1II and [RuIII(tda-κ-N3O2)(py)(H2O)ax]+, 2III(H2O)+. Complex 1II has been characterized by single-crystal XRD in the solid state and in solution by NMR spectroscopy. The redox properties of 1II and 2III(H2O)+ have been thoroughly investigated by means of cyclic voltammetry and differential pulse voltammetry. Complex 2II(H2O) displays poor catalytic activity with regard to the oxidation of water to dioxygen, and its properties have been analyzed on the basis of foot of the wave analysis and catalytic Tafel plots. The activity of 2II(H2O) has been compared with related water oxidation catalysts (WOCs) previously described in the literature. Despite its moderate activity, 2II(H2O) constitutes the cornerstone that has triggered the rationalization of the different factors that govern overpotentials as well as efficiencies in molecular WOCs. The present work uncovers the interplay between different parameters, namely, coordination number, number of anionic groups bonded to the first-coordination sphere of the metal center, water oxidation catalysis overpotential, pKa and hydrogen bonding, and the performance of a given WOC. It thus establishes the basic principles for the design of efficient WOCs operating at low overpotentials.},
doi = {10.1021/acscatal.7b01860},
journal = {ACS Catalysis},
number = 10,
volume = 7,
place = {United States},
year = 2017,
month = 8
}

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  • Energy storage and conversion schemes based on environmentally benign chemical fuels will require the discovery of faster, cheaper, and more robust catalysts for the oxygen evolution reaction (OER). Although pendant bases have led to enhanced turnover frequencies with non-aqueous substrates, their effect on the catalytic behavior of molecular water oxidation catalysts has received little attention. Herein, the syntheses, structures, and catalytic activities of new iron complexes with pendant bases are reported. Of these, the complex [Fe(mepydz)4(CH3CN)2](OTf)2 (mepydz = N,N'-dimethyl-N,N'-bis(pyridazin-3-ylmethyl)ethane-1,2-diamine, OTf = trifluoromethanesulonate) (8(CH3CN)22+) is the most active catalyst. Initial turnover frequencies of 141 h-1 and 24 h-1 were measured usingmore » ceric ammonium nitrate at pH 0.7 and sodium periodate at pH 4.7, respectively. At pH 4.7, 8(CH3CN)22+ the initial turnover frequency is 70% faster than the structurally analogous complex without ancillary proton relays. These results demonstrate that the incorporation of pendant bases into molecular water oxidation catalysts is a synthetic principle that should be considered in the development of new OER catalysts. This work was supported by Laboratory Directed Research and Development program at Pacific Northwest National Laboratory (PNNL). PNNL is operated by Battelle for the US Department of Energy.« less
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