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Title: Effect of Redox Active Ligands on the Electrochemical Properties of Manganese Tricarbonyl Complexes

Abstract

The synthesis, structural characterization, and electrochemical behavior of the neutral Mn(azpy)(CO) 3(Br) 4 (azpy = 2-phenylazopyridine) complex is reported and compared with its structural analogue Mn(bipy)(CO) 3(Br) 1 (bipy = 2,2'-bipyridine). 4 exhibits reversible two-electron reduction at a mild potential (-0.93 V vs Fc +/0 in acetonitrile) in contrast to 1, which exhibits two sequential one-electron reductions at -1.68 V and -1.89 V vs Fc +/0 in acetonitrile. The key electronic structure differences between 1 and 4 that lead to disparate electrochemical properties are investigated using a combination of Mn-K-edge X-ray absorption spectroscopy (XAS), Mn-Kβ X-ray emission spectroscopy (XES), and density functional theory (DFT) on 1, 4, their debrominated analogues, [Mn(L)(CO) 3(CH 3CN)][CF 3SO 3] (L = bipy 2, azpy 5), and two-electron reduced counterparts [Mn(bipy)(CO) 3][K(18-crown-6)] 3 and [Mn(azpy)(CO)3][Cp2Co] 6. The results reveal differences in the distribution of electrons about the CO and bidentate ligands (bipy and azpy), particularly upon formation of the highly reduced, formally Mn(-1) species. The data show that the degree of ligand noninnocence and resulting redox-activity in Mn(L)(CO) 3 type complexes impacts not only the reducing power of such systems, but the speciation of the reduced complexes via perturbation of the monomer-dimer equilibrium in themore » singly reduced Mn(0) state. In conclusion, this study highlights the role of redox-active ligands in tuning the reactivity of metal centers involved in electrocatalytic transformations.« less

Authors:
ORCiD logo [1]; ORCiD logo [2];  [2]; ORCiD logo [2]; ORCiD logo [3]
  1. Stanford Univ., CA (United States). Dept. of Chemistry; SLAC National Accelerator Lab., Menlo Park, CA (United States). Stanford Synchrotron Radiation Lightsource (SSRL)
  2. Stanford Univ., CA (United States). Dept. of Chemistry
  3. SLAC National Accelerator Lab., Menlo Park, CA (United States). Stanford Synchrotron Radiation Lightsource (SSRL)
Publication Date:
Research Org.:
SLAC National Accelerator Lab., Menlo Park, CA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23); National Science Foundation (NSF)
OSTI Identifier:
1532470
Grant/Contract Number:  
AC02-76SF00515; CHE-1213403; 2017-4-Waymouth; P41GM103393
Resource Type:
Accepted Manuscript
Journal Name:
Inorganic Chemistry
Additional Journal Information:
Journal Volume: 58; Journal Issue: 11; Journal ID: ISSN 0020-1669
Publisher:
American Chemical Society (ACS)
Country of Publication:
United States
Language:
English

Citation Formats

Matson, Benjamin D., McLoughlin, Elizabeth A., Armstrong, Keith C., Waymouth, Robert M., and Sarangi, Ritimukta. Effect of Redox Active Ligands on the Electrochemical Properties of Manganese Tricarbonyl Complexes. United States: N. p., 2019. Web. doi:10.1021/acs.inorgchem.9b00652.
Matson, Benjamin D., McLoughlin, Elizabeth A., Armstrong, Keith C., Waymouth, Robert M., & Sarangi, Ritimukta. Effect of Redox Active Ligands on the Electrochemical Properties of Manganese Tricarbonyl Complexes. United States. doi:10.1021/acs.inorgchem.9b00652.
Matson, Benjamin D., McLoughlin, Elizabeth A., Armstrong, Keith C., Waymouth, Robert M., and Sarangi, Ritimukta. Thu . "Effect of Redox Active Ligands on the Electrochemical Properties of Manganese Tricarbonyl Complexes". United States. doi:10.1021/acs.inorgchem.9b00652.
@article{osti_1532470,
title = {Effect of Redox Active Ligands on the Electrochemical Properties of Manganese Tricarbonyl Complexes},
author = {Matson, Benjamin D. and McLoughlin, Elizabeth A. and Armstrong, Keith C. and Waymouth, Robert M. and Sarangi, Ritimukta},
abstractNote = {The synthesis, structural characterization, and electrochemical behavior of the neutral Mn(azpy)(CO)3(Br) 4 (azpy = 2-phenylazopyridine) complex is reported and compared with its structural analogue Mn(bipy)(CO)3(Br) 1 (bipy = 2,2'-bipyridine). 4 exhibits reversible two-electron reduction at a mild potential (-0.93 V vs Fc+/0 in acetonitrile) in contrast to 1, which exhibits two sequential one-electron reductions at -1.68 V and -1.89 V vs Fc+/0 in acetonitrile. The key electronic structure differences between 1 and 4 that lead to disparate electrochemical properties are investigated using a combination of Mn-K-edge X-ray absorption spectroscopy (XAS), Mn-Kβ X-ray emission spectroscopy (XES), and density functional theory (DFT) on 1, 4, their debrominated analogues, [Mn(L)(CO)3(CH3CN)][CF3SO3] (L = bipy 2, azpy 5), and two-electron reduced counterparts [Mn(bipy)(CO)3][K(18-crown-6)] 3 and [Mn(azpy)(CO)3][Cp2Co] 6. The results reveal differences in the distribution of electrons about the CO and bidentate ligands (bipy and azpy), particularly upon formation of the highly reduced, formally Mn(-1) species. The data show that the degree of ligand noninnocence and resulting redox-activity in Mn(L)(CO)3 type complexes impacts not only the reducing power of such systems, but the speciation of the reduced complexes via perturbation of the monomer-dimer equilibrium in the singly reduced Mn(0) state. In conclusion, this study highlights the role of redox-active ligands in tuning the reactivity of metal centers involved in electrocatalytic transformations.},
doi = {10.1021/acs.inorgchem.9b00652},
journal = {Inorganic Chemistry},
number = 11,
volume = 58,
place = {United States},
year = {2019},
month = {5}
}

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This content will become publicly available on May 16, 2020
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