Controlling Proton Delivery through Catalyst Structural Dynamics.
The fastest synthetic molecular catalysts for H2production and oxidation emulate components of the active site of hydrogenases. The critical role of controlled structural dynamics is recognized for many enzymes, including hydrogenases, but is largely neglected in designing synthetic catalysts. Our results demonstrate the impact of controlling structural dynamics on H2production rates for [Ni(PPh2NC6H4R2)2]2+catalysts (R=n-hexyl, n-decyl, n-tetradecyl, n-octadecyl, phenyl, or cyclohexyl). The turnover frequencies correlate inversely with the rates of chair-boat ring inversion of the ligand, since this dynamic process governs protonation at either catalytically productive or non-productive sites. These results demonstrate that the dynamic processes involved in proton delivery can be controlled through modification of the outer coordination sphere, in a manner similar to the role of the protein architecture in many enzymes. As a design parameter, controlling structural dynamics can increase H2production rates by three orders of magnitude with a minimal increase in overpotential.
Center for Molecular Electrocatalysis, Pacific Northwest National Laboratory, P.O. Box 999, K2-57, Richland, WA, 99352, USA.|221 Science Center, State University of New York at Fredonia, Fredonia, NY, 14063, USA.
Allan Jay P
AJ
Cardenas
Center for Molecular Electrocatalysis, Pacific Northwest National Laboratory, P.O. Box 999, K2-57, Richland, WA, 99352, USA.
Bojana
B
Ginovska
Center for Molecular Electrocatalysis, Pacific Northwest National Laboratory, P.O. Box 999, K2-57, Richland, WA, 99352, USA.
Neeraj
N
Kumar
Center for Molecular Electrocatalysis, Pacific Northwest National Laboratory, P.O. Box 999, K2-57, Richland, WA, 99352, USA.
Jianbo
J
Hou
Center for Molecular Electrocatalysis, Pacific Northwest National Laboratory, P.O. Box 999, K2-57, Richland, WA, 99352, USA.
Simone
S
Raugei
Center for Molecular Electrocatalysis, Pacific Northwest National Laboratory, P.O. Box 999, K2-57, Richland, WA, 99352, USA.
Monte L
ML
Helm
Center for Molecular Electrocatalysis, Pacific Northwest National Laboratory, P.O. Box 999, K2-57, Richland, WA, 99352, USA.
Aaron M
AM
Appel
Center for Molecular Electrocatalysis, Pacific Northwest National Laboratory, P.O. Box 999, K2-57, Richland, WA, 99352, USA.
R Morris
RM
Bullock
Center for Molecular Electrocatalysis, Pacific Northwest National Laboratory, P.O. Box 999, K2-57, Richland, WA, 99352, USA. molly.ohagan@pnnl.com.
Molly
M
O'Hagan
D002384:Catalysis; D055664:Electrochemical Techniques; D004566:Electrodes; D006859:Hydrogen / Q000737:chemistry*; D015394:Molecular Structure; D009532:Nickel / Q000737:chemistry*; D009942:Organometallic Compounds / Q000737:chemistry*; D011522:Protons; D013816:Thermodynamics
D009942:Organometallic Compounds; D011522:Protons; D009532:Nickel; D006859:Hydrogen
artificial enzymes; electrocatalysis; homogeneous catalysis; hydrogen production; structural dynamics