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Title: Amino acid modified Ni catalyst exhibits reversible H 2 oxidation/production over a broad pH range at elevated temperatures

Abstract

Hydrogenases interconvert H 2 and protons at high rates and with high energy efficiencies, providing inspiration for the development of molecular catalysts. Studies designed to determine how the protein scaffold can influence a catalytically active site has led to the synthesis of amino acid derivatives, [Ni(P Cy 2N Amino acid2) 2] 2+ (CyAA), of [Ni(P R 2N R' 2) 2] 2+ complexes. It is shown that these CyAA derivatives can catalyze fully reversible H 2 production/oxidation, a feature reminiscent of enzymes. The reversibility is achieved in acidic aqueous solutions, 0.25% H 2/Ar, and elevated temperatures (tested up to 348 K) for the glycine (CyGly), arginine (CyArg), and arginine methyl ester (CyArgOMe) derivatives. As expected for a reversible process, the activity is dependent upon H 2 and proton concentration. CyArg is significantly faster in both directions than the other two derivatives (~300 s -1 H 2 production and 20 s -1 H 2 oxidation; pH = 1, 348 K). The significantly slower rates for CyArgOMe (35 s -1 production and 7 s -1 oxidation) compared to CyArg suggests an important role for the COOH group during catalysis. That CyArg is faster than CyGly (3 s -1 production and 4 s -1more » oxidation under the same conditions) suggests that the additional structural features imparted by the guanidinium groups facilitate fast and reversible H 2 addition/release. Furthermore, these observations demonstrate that appended, outer coordination sphere amino acids work in synergy with the active site and can play an equally important role for synthetic molecular electrocatalysts as the protein scaffold does for redox active enzymes.« less

Authors:
 [1];  [1];  [2];  [1]
  1. Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
  2. Pacific Northwest National Lab. (PNNL), Richland, WA (United States); REC Silicon, Moses Lake, WA (United States)
Publication Date:
Research Org.:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States). Environmental Molecular Sciences Lab. (EMSL)
Sponsoring Org.:
USDOE
OSTI Identifier:
1166832
Report Number(s):
PNNL-SA-104694
Journal ID: ISSN 0027-8424; 44681; KC0302010
Grant/Contract Number:  
AC05-76RL01830
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Proceedings of the National Academy of Sciences of the United States of America
Additional Journal Information:
Journal Volume: 111; Journal Issue: 46; Journal ID: ISSN 0027-8424
Publisher:
National Academy of Sciences, Washington, DC (United States)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; reversible H2 oxidation/production catalysis; bioinspired catalyst; outer coordination sphere; homogeneous electrocatalysis; hydrogenase mimics; Environmental Molecular Sciences Laboratory; amino acid catalysts; outer coordination; sphere

Citation Formats

Dutta, Arnab, DuBois, Daniel L., Roberts, John A. S., and Shaw, Wendy J. Amino acid modified Ni catalyst exhibits reversible H2 oxidation/production over a broad pH range at elevated temperatures. United States: N. p., 2014. Web. doi:10.1073/pnas.1416381111.
Dutta, Arnab, DuBois, Daniel L., Roberts, John A. S., & Shaw, Wendy J. Amino acid modified Ni catalyst exhibits reversible H2 oxidation/production over a broad pH range at elevated temperatures. United States. doi:10.1073/pnas.1416381111.
Dutta, Arnab, DuBois, Daniel L., Roberts, John A. S., and Shaw, Wendy J. Mon . "Amino acid modified Ni catalyst exhibits reversible H2 oxidation/production over a broad pH range at elevated temperatures". United States. doi:10.1073/pnas.1416381111. https://www.osti.gov/servlets/purl/1166832.
@article{osti_1166832,
title = {Amino acid modified Ni catalyst exhibits reversible H2 oxidation/production over a broad pH range at elevated temperatures},
author = {Dutta, Arnab and DuBois, Daniel L. and Roberts, John A. S. and Shaw, Wendy J.},
abstractNote = {Hydrogenases interconvert H2 and protons at high rates and with high energy efficiencies, providing inspiration for the development of molecular catalysts. Studies designed to determine how the protein scaffold can influence a catalytically active site has led to the synthesis of amino acid derivatives, [Ni(PCy2NAmino acid2)2]2+ (CyAA), of [Ni(PR2NR'2)2]2+ complexes. It is shown that these CyAA derivatives can catalyze fully reversible H2 production/oxidation, a feature reminiscent of enzymes. The reversibility is achieved in acidic aqueous solutions, 0.25% H2/Ar, and elevated temperatures (tested up to 348 K) for the glycine (CyGly), arginine (CyArg), and arginine methyl ester (CyArgOMe) derivatives. As expected for a reversible process, the activity is dependent upon H2 and proton concentration. CyArg is significantly faster in both directions than the other two derivatives (~300 s-1 H2 production and 20 s-1 H2 oxidation; pH = 1, 348 K). The significantly slower rates for CyArgOMe (35 s-1 production and 7 s-1 oxidation) compared to CyArg suggests an important role for the COOH group during catalysis. That CyArg is faster than CyGly (3 s-1 production and 4 s-1 oxidation under the same conditions) suggests that the additional structural features imparted by the guanidinium groups facilitate fast and reversible H2 addition/release. Furthermore, these observations demonstrate that appended, outer coordination sphere amino acids work in synergy with the active site and can play an equally important role for synthetic molecular electrocatalysts as the protein scaffold does for redox active enzymes.},
doi = {10.1073/pnas.1416381111},
journal = {Proceedings of the National Academy of Sciences of the United States of America},
issn = {0027-8424},
number = 46,
volume = 111,
place = {United States},
year = {2014},
month = {11}
}

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Works referenced in this record:

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