TY - JOUR
T1 - Redox Activity of Oxo-Bridged Iridium Dimers in an N,O-Donor Environment
T2 - Characterization of Remarkably Stable Ir(IV,V) Complexes
AU - Sinha, Shashi Bhushan
AU - Shopov, Dimitar Y.
AU - Sharninghausen, Liam S.
AU - Stein, Christopher J.
AU - Mercado, Brandon Q.
AU - Balcells, David
AU - Pedersen, Thomas Bondo
AU - Reiher, Markus
AU - Brudvig, Gary W.
AU - Crabtree, Robert H.
N1 - Funding Information:
This work (S.B.S, D.Y.S and L.S.S) was supported the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences Division of Chemical Sciences, Geosciences, and Biosciences under Award Number DE-SC0001059 as part of the Argonne-Northwestern Solar Energy Research (ANSER) Energy Frontier Research Center (spectroscopy and characterization) and under Award Number DEFG02-07ER15909 (synthesis). D.B. and T.B.P were supported by the Research Council of Norway through a Centre of Excellence grant (Grant No. 179568/V30) and the Norwegian Supercomputing Program (NOTUR) through a grant for computing time (Grant No. NN4654K). DB also acknowledges the EU REA for a Marie Curie Fellowship (Grant CompuWOC/618303). C.J.S. thanks the Fonds der Chemischen Industrie for a Kekule Ph.D. fellowship. M.R. acknowledges support from the Schweizerischer Nationalfonds (Project No. 20020-169120). Dr. Min Li and Zishan Wu at the Yale Materials Characterization Core are acknowledged for collection of data by X-ray Photoelectron Spectroscopy. We would like to thank the Advanced Light Source (ALS) for performing synchrotron X-ray diffraction of gB1IV,V. The ALS is supported by the Director, Office of Science, Office of Basic Energy Sciences, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.
PY - 2017/7/19
Y1 - 2017/7/19
N2 - Chemical and electrochemical oxidation or reduction of our recently reported Ir(IV,IV) mono-μ-oxo dimers results in the formation of fully characterized Ir(IV,V) and Ir(III,III) complexes. The Ir(IV,V) dimers are unprecedented and exhibit remarkable stability under ambient conditions. This stability and modest reduction potential of 0.99 V vs NHE is in part attributed to complete charge delocalization across both Ir centers. Trends in crystallographic bond lengths and angles shed light on the structural changes accompanying oxidation and reduction. The similarity of these mono-μ-oxo dimers to our Ir "blue solution" water-oxidation catalyst gives insight into potential reactive intermediates of this structurally elusive catalyst. Additionally, a highly reactive material, proposed to be a Ir(V,V) μ-oxo species, is formed on electrochemical oxidation of the Ir(IV,V) complex in organic solvents at 1.9 V vs NHE. Spectroelectrochemistry shows reversible conversion between the Ir(IV,V) and proposed Ir(V,V) species without any degradation, highlighting the exceptional oxidation resistance of the 2-(2-pyridinyl)-2-propanolate (pyalk) ligand and robustness of these dimers. The Ir(III,III), Ir(IV,IV) and Ir(IV,V) redox states have been computationally studied both with DFT and multiconfigurational calculations. The calculations support the stability of these complexes and provide further insight into their electronic structures.
AB - Chemical and electrochemical oxidation or reduction of our recently reported Ir(IV,IV) mono-μ-oxo dimers results in the formation of fully characterized Ir(IV,V) and Ir(III,III) complexes. The Ir(IV,V) dimers are unprecedented and exhibit remarkable stability under ambient conditions. This stability and modest reduction potential of 0.99 V vs NHE is in part attributed to complete charge delocalization across both Ir centers. Trends in crystallographic bond lengths and angles shed light on the structural changes accompanying oxidation and reduction. The similarity of these mono-μ-oxo dimers to our Ir "blue solution" water-oxidation catalyst gives insight into potential reactive intermediates of this structurally elusive catalyst. Additionally, a highly reactive material, proposed to be a Ir(V,V) μ-oxo species, is formed on electrochemical oxidation of the Ir(IV,V) complex in organic solvents at 1.9 V vs NHE. Spectroelectrochemistry shows reversible conversion between the Ir(IV,V) and proposed Ir(V,V) species without any degradation, highlighting the exceptional oxidation resistance of the 2-(2-pyridinyl)-2-propanolate (pyalk) ligand and robustness of these dimers. The Ir(III,III), Ir(IV,IV) and Ir(IV,V) redox states have been computationally studied both with DFT and multiconfigurational calculations. The calculations support the stability of these complexes and provide further insight into their electronic structures.
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U2 - 10.1021/jacs.7b04874
DO - 10.1021/jacs.7b04874
M3 - Article
C2 - 28648068
AN - SCOPUS:85024902184
VL - 139
SP - 9672
EP - 9683
JO - Journal of the American Chemical Society
JF - Journal of the American Chemical Society
SN - 0002-7863
IS - 28
ER -