Moving Protons and Electrons in Biomimetic Systems

Warren, Jeffrey J.; Mayer, James M.

doi:10.1021/acs.biochem.5b00025

Cited by 93 publications

(86 citation statements)

References 236 publications

(306 reference statements)

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…64,206–208 Studies on PCET to N 2 , N 2 H 2 , N 2 H 4 , and other fragments of relevance to N 2 reduction are needed, 99,209 because such reactions are involved in the part of the nitrogenase mechanism spanning the E 4 to E 8 levels. We also note that systems that engage in PCET often involve hydrogen bonds, 210 but to our knowledge there are not yet any examples of hydrogen bonding to an N 2 unit in a transition-metal complex.…”

Section: Discussionmentioning

confidence: 85%

Insight into the Iron–Molybdenum Cofactor of Nitrogenase from Synthetic Iron Complexes with Sulfur, Carbon, and Hydride Ligands

2016

View full text Add to dashboard Cite

Nitrogenase enzymes are used by microorganisms for converting atmospheric N2 to ammonia, which provides an essential source of N atoms for higher organisms. The active site of the molybdenum-dependent nitrogenase is the unique carbide-containing iron-sulfur cluster called the iron-molybdenum cofactor (FeMoco). On the FeMoco, N2 binding is suggested to occur at one or more iron atoms, but the structures of the catalytic intermediates are not clear. In order to establish the feasibility of different potential mechanistic steps during biological N2 reduction, chemists have prepared iron complexes that mimic various structural aspects of the iron sites in FeMoco. This reductionist approach gives mechanistic insight, and also uncovers fundamental principles that could be used more broadly for small molecule activation. Here, we review recent results and highlight directions for future research. In one direction, synthetic iron complexes have now been shown to bind N2, break the N-N triple bond, and produce ammonia catalytically. Carbon and sulfur based donors have been incorporated into the ligand spheres of Fe-N2 complexes to show how these atoms may influence the structure and reactivity of the FeMoco. Hydrides have been incorporated into synthetic systems, which can bind N2, reduce some nitrogenase substrates, and/or reductively eliminate H2 to generate reduced iron centers. Though some carbide-containing iron clusters are known, none yet have sulfide bridges or high-spin iron atoms like the FeMoco.

show abstract

Section: Discussionmentioning

confidence: 85%

Insight into the Iron–Molybdenum Cofactor of Nitrogenase from Synthetic Iron Complexes with Sulfur, Carbon, and Hydride Ligands

2016

View full text Add to dashboard Cite

show abstract

“…'Proton-coupled electron transfer' (PCET) describes any elementary step (or series of elementary steps) in which both a proton and an electron are exchanged [1][2][3][4][5][6][7][8][9]. Within this broad definition, further distinctions may be drawn: if the proton and electron move simultaneously, the elementary step is referred to as a concerted PCET.…”

Section: Introductionmentioning

confidence: 99%

Proton-Coupled Electron Transfer in Organic Synthesis: Fundamentals, Applications, and Opportunities

Miller

Tarantino

Knowles

2016

Topics in Current Chemistry Collections

View full text Add to dashboard Cite

Proton-coupled electron transfers (PCETs) are unconventional redox processes in which both protons and electrons are exchanged, often in a concerted elementary step. While PCET is now recognized to play a central a role in biological redox catalysis and inorganic energy conversion technologies, its applications in organic synthesis are only beginning to be explored. In this chapter we aim to highlight the origins, development and evolution of PCET processes most relevant to applications in organic synthesis. Particular emphasis is given to the ability of PCET to serve as a non-classical mechanism for homolytic bond activation that is complimentary to more traditional hydrogen atom transfer processes, enabling the direct generation of valuable organic radical intermediates directly from their native functional group precursors under comparatively mild catalytic conditions. The synthetically advantageous features of PCET reactivity are described in detail, along with examples from the literature describing the PCET activation of common organic functional groups.

show abstract

“…One of the key features of this mechanism is the role of PCET, 27 which avoids the accumulation of hydride intermediates in the native enzyme. Clearly, some open questions still remain, such as the factors that affect the isomerization equilibrium between H sred H + and H hyd .…”

mentioning

confidence: 99%

Direct Observation of an Iron-Bound Terminal Hydride in [FeFe]-Hydrogenase by Nuclear Resonance Vibrational Spectroscopy

et al. 2017

View full text Add to dashboard Cite

[FeFe]-hydrogenases catalyze the reversible reduction of protons to molecular hydrogen with extremely high efficiency. The active site (“H-cluster”) consists of a [4Fe–4S]H cluster linked through a bridging cysteine to a [2Fe]H subsite coordinated by CN− and CO ligands featuring a dithiol-amine moiety that serves as proton shuttle between the protein proton channel and the catalytic distal iron site (Fed). Although there is broad consensus that an iron-bound terminal hydride species must occur in the catalytic mechanism, such a species has never been directly observed experimentally. Here, we present FTIR and nuclear resonance vibrational spectroscopy (NRVS) experiments in conjunction with density functional theory (DFT) calculations on an [FeFe]-hydrogenase variant lacking the amine proton shuttle which is stabilizing a putative hydride state. The NRVS spectra unequivocally show the bending modes of the terminal Fe–H species fully consistent with widely accepted models of the catalytic cycle.

show abstract

Moving Protons and Electrons in Biomimetic Systems

Cited by 93 publications

References 236 publications

Insight into the Iron–Molybdenum Cofactor of Nitrogenase from Synthetic Iron Complexes with Sulfur, Carbon, and Hydride Ligands

Insight into the Iron–Molybdenum Cofactor of Nitrogenase from Synthetic Iron Complexes with Sulfur, Carbon, and Hydride Ligands

Proton-Coupled Electron Transfer in Organic Synthesis: Fundamentals, Applications, and Opportunities

Direct Observation of an Iron-Bound Terminal Hydride in [FeFe]-Hydrogenase by Nuclear Resonance Vibrational Spectroscopy

Contact Info

Product

Resources

About