Conformational mobility and pendent base effects on electrochemistry of synthetic analogues of the [FeFe]-hydrogenase active site

Danielle J. Crouthers; Jason A. Denny; Ryan D. Bethel; David G. Munoz; Marcetta Y. Darensbourg

doi:10.1021/om500023j

Conformational mobility and pendent base effects on electrochemistry of synthetic analogues of the [FeFe]-hydrogenase active site

Danielle J. Crouthers, Jason A. Denny, Ryan D. Bethel, David G. Munoz, Marcetta Y. Darensbourg^*

^*Corresponding author for this work

Chemistry

Research output: Contribution to journal › Article › peer-review

44 Scopus citations

Abstract

Dynamic NMR (¹³C and ¹H) studies of (μ-SCH₂XCH₂S)[Fe-(CO)₃]₂ complexes (X = CR₂, NR) were utilized to examine the fluxional processes that are important in the [FeFe]-hydrogenase active site models, where an open site for proton/hydrogen binding, achieved by configurational mobility of the Fe(CO)₃ unit, is required for electrocatalysis of proton reduction. In order to interrogate the effects of fluxional mobility on electrochemical response to added acid, energy barriers for the CO site exchange in Fe(CO)₃ rotors were determined for nitrogen-and carbon-based bridgehead complexes. The effect of the methyl substituent in both the NH/NCH₃ and CH₂/C(CH₃)₂ cases is to lower the Fe(CO)₃ rotational activation barrier relative to the NH or CH₂ analogues. Although the C(CH₃)₂ case has the lowest Fe(CO)₃ rotational barrier, its performance as a proton reduction electrocatalyst is 2-fold less than that for the X = NR species, indicating the proton-directing effect of the pendent base on catalytic efficiency.

Original language	English (US)
Pages (from-to)	4747-4755
Number of pages	9
Journal	Organometallics
Volume	33
Issue number	18
DOIs	https://doi.org/10.1021/om500023j
State	Published - Sep 22 2014

ASJC Scopus subject areas

Physical and Theoretical Chemistry
Organic Chemistry
Inorganic Chemistry

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title = "Conformational mobility and pendent base effects on electrochemistry of synthetic analogues of the [FeFe]-hydrogenase active site",

abstract = "Dynamic NMR (13C and 1H) studies of (μ-SCH2XCH2S)[Fe-(CO)3]2 complexes (X = CR2, NR) were utilized to examine the fluxional processes that are important in the [FeFe]-hydrogenase active site models, where an open site for proton/hydrogen binding, achieved by configurational mobility of the Fe(CO)3 unit, is required for electrocatalysis of proton reduction. In order to interrogate the effects of fluxional mobility on electrochemical response to added acid, energy barriers for the CO site exchange in Fe(CO)3 rotors were determined for nitrogen-and carbon-based bridgehead complexes. The effect of the methyl substituent in both the NH/NCH3 and CH2/C(CH3)2 cases is to lower the Fe(CO)3 rotational activation barrier relative to the NH or CH2 analogues. Although the C(CH3)2 case has the lowest Fe(CO)3 rotational barrier, its performance as a proton reduction electrocatalyst is 2-fold less than that for the X = NR species, indicating the proton-directing effect of the pendent base on catalytic efficiency.",

author = "Crouthers, {Danielle J.} and Denny, {Jason A.} and Bethel, {Ryan D.} and Munoz, {David G.} and Darensbourg, {Marcetta Y.}",

note = "Publisher Copyright: {\textcopyright} 2014 American Chemical Society.",

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T1 - Conformational mobility and pendent base effects on electrochemistry of synthetic analogues of the [FeFe]-hydrogenase active site

AU - Crouthers, Danielle J.

AU - Denny, Jason A.

AU - Bethel, Ryan D.

AU - Munoz, David G.

AU - Darensbourg, Marcetta Y.

PY - 2014/9/22

Y1 - 2014/9/22

N2 - Dynamic NMR (13C and 1H) studies of (μ-SCH2XCH2S)[Fe-(CO)3]2 complexes (X = CR2, NR) were utilized to examine the fluxional processes that are important in the [FeFe]-hydrogenase active site models, where an open site for proton/hydrogen binding, achieved by configurational mobility of the Fe(CO)3 unit, is required for electrocatalysis of proton reduction. In order to interrogate the effects of fluxional mobility on electrochemical response to added acid, energy barriers for the CO site exchange in Fe(CO)3 rotors were determined for nitrogen-and carbon-based bridgehead complexes. The effect of the methyl substituent in both the NH/NCH3 and CH2/C(CH3)2 cases is to lower the Fe(CO)3 rotational activation barrier relative to the NH or CH2 analogues. Although the C(CH3)2 case has the lowest Fe(CO)3 rotational barrier, its performance as a proton reduction electrocatalyst is 2-fold less than that for the X = NR species, indicating the proton-directing effect of the pendent base on catalytic efficiency.

AB - Dynamic NMR (13C and 1H) studies of (μ-SCH2XCH2S)[Fe-(CO)3]2 complexes (X = CR2, NR) were utilized to examine the fluxional processes that are important in the [FeFe]-hydrogenase active site models, where an open site for proton/hydrogen binding, achieved by configurational mobility of the Fe(CO)3 unit, is required for electrocatalysis of proton reduction. In order to interrogate the effects of fluxional mobility on electrochemical response to added acid, energy barriers for the CO site exchange in Fe(CO)3 rotors were determined for nitrogen-and carbon-based bridgehead complexes. The effect of the methyl substituent in both the NH/NCH3 and CH2/C(CH3)2 cases is to lower the Fe(CO)3 rotational activation barrier relative to the NH or CH2 analogues. Although the C(CH3)2 case has the lowest Fe(CO)3 rotational barrier, its performance as a proton reduction electrocatalyst is 2-fold less than that for the X = NR species, indicating the proton-directing effect of the pendent base on catalytic efficiency.

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Conformational mobility and pendent base effects on electrochemistry of synthetic analogues of the [FeFe]-hydrogenase active site

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