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Detailed knowledge about its catalytic process is important for exploiting [Fe]-hydrogenase—an enzyme that cleaves and produces H₂—for technological purposes. This study presents an atomic-resolution crystal structure of a substrate-bound closed active form of the enzyme and a precise catalytic cycle.

Ferritin controls iron concentrations by storing Fe(III), but the mechanism by which Fe(II) is bound and trafficked into the protein core after oxidation remains controversial. Spectroscopic methods in combination with labeling and competition assays now define a mechanism conserved from archaea to humans.

The activation of dioxygen at metal centres, and subsequent functionalization of unactivated C‒H bonds, requires the generation of high-energy radical intermediates that often result in undesirable side reactions. Now an elusive oxygen-derived reactive iron(II)–radical intermediate is spectroscopically characterized as part of a strategy to stabilize phenoxyl radical cofactors during substrate oxidation reactions.

Complexes of iron in high oxidation states play a pivotal role as active intermediates in numerous catalytic processes. Now, using a multimethod approach on a single molecular system, it has been shown that a stable high-valent Fe(VI) nitride can be converted to a reactive, superoxidized, heptavalent Fe(VII) nitride.

Transition metal complexes that display slow magnetic relaxation show promise for information storage, but our mechanistic understanding of the magnetic relaxation of such compounds remains limited. Here, the authors spectroscopically and computationally characterize the strength of spin–phonon couplings, which play an important role in the relaxation process.

By obtaining structural snapshots of the catalytic cycle of NADH:quinone oxidoreductase from Vibrio cholerae, the authors uncover its mechanism. They show how electrons are shuttled and determine the importance of the [2Fe-2S] cluster in the movement of the electron transfer switch.

A synthetic complex with a sulfur-rich coordination sphere is described that, upon reduction, breaks an Fe–S bond and binds N₂, providing a model for the iron–molybdenum cofactor used by nitrogenase enzymes to produce ammonia.

For more than a decade, single-molecule magnets have relied on multinuclear transition metal clusters and lanthanide compounds. Now, a mononuclear, two-coordinate iron(I) complex has shown that single transition metals can compete with the lanthanides when certain design principles from magnetochemistry are borne in mind.

Iron coordination complexes can be used to gain insight on biologically relevant iron-oxygen compounds generated in iron metalloenzymes. Here, the authors characterise a μ-1,2-hydroperoxo Fe^IIIFe^III and a μ-1,2-peroxo Fe^IVFe^III, and study their reactivity in C-H activation.

Radicals of heavy main-group elements represent important intermediates in chemical synthesis, yet few have been isolated. Here the authors stabilize neutral stibinyl and bismuthinyl radicals using gallium-based ligands, and reduce the former to afford a Ga=Sb double bond-containing complex.

Attempts to bend and twist multiple bonds in order to alter their reactivities have thus far been met with only modest success. Here, Braunschweig and colleagues isolate double-bond-containing boron-based species and their 90°-twisted diradical analogs, thanks to their stabilization with Lewis basic units.

The functions of the highly reduced mitochondria (mitosomes) of microsporidians are not well-characterized. Here, the authors show that theTrachipleistophora hominismitosome is the site of iron–sulfur cluster assembly and that its retention is likely linked to its role in cytosolic and nuclear iron–sulfur protein maturation.

The four-coordinate iron sites of typical iron–sulfur clusters rarely react with small molecules, implicating three-coordinate iron in many catalytic cycles. Now, a [4Fe-3S] cluster featuring three-coordinate iron sulfide that resembles the proposed substrate binding site has been synthesized. This cluster shows biomimetic reactivity with a low-spin electronic configuration.