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A new series of homodinuclear iron complexes as models of the [FeFe]-hydrogenase active site was prepared and characterized. The complexes of the general formula [Fe2(mcbdt)(CO)5PPh2R] (mcbdt = benzene-1,2-dithiol-3-carboxylic acid) feature covalent tethers that link the mcbdt ligand with the phosphine ligands which are terminally coordinated to one of the Fe centres. The synthetic feasability of the concept is demonstrated with the preparation of three novel complexes. A detailed theoretical investigation showes that by introducing a rigid covalent link between the phosphine and the bridging dithiolate ligands, the rotation of the Fe(CO)2P unit is hindered and higher rotation barriers were calculated compared to non-linked reference complexes. The concept of restricting Fe(L)3 rotation is an approach to kinetically stabilize terminal hydrides which are reactive intermediates in catalytic proton reduction cycles of the enzymes.
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http://dx.doi.org/10.1039/c8dt05148h | DOI Listing |
J Am Chem Soc
August 2025
Department of Chemistry, University of California, Davis, California 95616, United States.
[FeFe] hydrogenases are highly efficient metalloenzymes that catalyze hydrogen conversion via a sophisticated active site cofactor known as the H-cluster. Biosynthesis of its [2Fe] subcluster, which contains CO, CN, and azadithiolate ligands, requires the action of several dedicated enzymes, including the radical -adenosyl-l-methionine (rSAM) enzyme HydE. HydE has been proposed to convert a mononuclear [Fe(II)(cysteinate)(CO)(CN)] precursor into a dimeric [Fe(SH)(CO)(CN)] complex, yet direct characterization of this product species has remained elusive.
View Article and Find Full Text PDFJ Am Chem Soc
July 2025
School of Chemical Sciences, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States.
The preparation, spectroscopy, and structure are described for [Fe(κ-cys)(CN)(CO)] ([]). Otherwise known as complex-B, this coordination complex is an early intermediate in the biosynthesis of the active site of the [FeFe]-hydrogenases. As confirmed by X-ray crystallography, the complex is octahedral with a tridentate cysteinate ligand.
View Article and Find Full Text PDFBiochemistry
June 2025
Biosciences Center, National Renewable Energy Laboratory, Golden, Colorado 80401, United States.
[FeFe]-Hydrogenases are structurally diverse enzymes that catalyze reversible H activation at a catalytic cofactor or H-cluster. The H-cluster is a [4Fe-4S] cubane linked by a cysteine thiolate to a diiron subsite containing unique CO, CN, and dithiomethylamine ligands. The established H-cluster resting state of [4Fe-4S]-[Fe-Fe], or H, functions in H binding and oxidation, or by proton-coupled reduction initiates H evolution.
View Article and Find Full Text PDFChembiochem
July 2025
Department of Chemistry, University of Oxford, Inorganic Chemistry Laboratory, South Parks Road, Oxford, OX1 3QR, UK.
The noncanonical amino acid, para-cyanophenylalanine (CNF), when incorporated into metalloproteins, functions as an infrared spectroscopic probe for the redox state of iron-sulfur clusters, offering a strategy for determining electron occupancy in the electron transport chains of complex metalloenzymes. A redshift of ≈1-2 cm in the nitrile (NC) stretching frequency is observed, following reduction of spinach ferredoxin modified to contain CNF close to its [2Fe-2S] center, and this shift is reversed on re-oxidation. We extend this to CNF positioned near to the proximal [4Fe-4S] cluster of the [FeFe] hydrogenase from Desulfovibrio desulfuricans.
View Article and Find Full Text PDFAdv Sci (Weinh)
June 2025
School of Science and Engineering, Shenzhen Key Laboratory of Innovative Drug Synthesis, The Chinese University of Hong Kong, Shenzhen, Guangdong, 518172, P. R. China.
Learning from nature has emerged as a promising strategy for catalyst development, wherein the remarkable performance of catalysts selected by nature over billions of years of evolution serves as a basis for the creative design of high-performance catalysts. Hydrogenases, with their exceptional catalytic activity in hydrogen oxidation and production, have been employed as prototypes for human learning to achieve better catalyst design. A comprehensive understanding of hydrogenases' structures and catalytic mechanisms is crucial to replicate and exceed their performance.
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