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

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:
Report Number(s):
BNL-114431-2017-JA
Journal ID: ISSN 2155-5435; R&D Project: CO026; KC0304030
Grant/Contract Number:
SC0012704
Type:
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)
Research Org:
Brookhaven National Laboratory (BNL), Upton, NY (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
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
OSTI Identifier:
1405933