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Photosystem II (PSII) contains Ca, which is essential to the oxygen-evolving activity of the catalytic MnCaO complex. Replacement of Ca with other redox-inactive metals results in a loss/decrease of oxygen-evolving activity. To investigate the role of Ca in this catalytic reaction, we investigate artificial Mn[M]O clusters redox-inactive metals [M] ([M] = Mg, Ca, Zn, Sr, and Y), which were synthesized by Tsui et al. (Nat Chem 5:293, 2013). The experimentally measured redox potentials (E) of these clusters are best described by the energy of their highest occupied molecular orbitals. Quantum chemical calculations showed that the valence of metals predominantly affects E(Mn), whereas the ionic radius of metals affects E(Mn) only slightly.
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http://dx.doi.org/10.1007/s11120-021-00846-y | DOI Listing |
Chem Asian J
August 2025
Department of Chemistry, Indian Institute of Technology Delhi, Hauz Khas, New Delhi, 110016, India.
The secondary coordination sphere (SCS) around the substrate binding site of a catalyst, such as a proton relay, formation of a hydrogen bonding network, and electrostatic effects, plays a critical role in controlling the selectivity and rate of oxygen reduction reaction (ORR). Herein, we report the ORR study of a series of Fe complexes having a uniform primary coordination sphere and an unlike SCS. The Fe(III) complex, lacking any secondary coordination sphere (SCS) modifications, exhibited slow oxygen reduction reaction (ORR) kinetics in the presence of decamethylferrocene (Fc) and trifluoroacetic acid (TFAH) in oxygen-saturated acetonitrile.
View Article and Find Full Text PDFNat Commun
August 2025
Department of Organic Chemistry, University of Chemistry and Technology, Prague, Prague, 166 28, Czech Republic.
In recent years, the catalytic activity of scandium triflate Sc(OTf) has attracted significant attention due to its robust Lewis acidity and the oxophilicity of Sc. These features have led to impressive progress in developing diverse organic reactions, including C-C bond formation. The Sc also facilitates single electron transfer in photoinduced reactions either by coordination to an organophotoredox catalyst, which modifies its redox reactivity, or by the formation of a scandium-superoxide anion complex after electron transfer from a light-absorbing redox-active compound.
View Article and Find Full Text PDFJ Am Chem Soc
August 2025
School of Chemistry, Trinity College Dublin, The University of Dublin, College Green, Dublin 2, Ireland.
Chlorophyll-based pigments are crucial mediators of redox processes in photosynthesis, serving as the primary electron donors in photosystems I and II. Despite their structural similarities, these pigments exhibit a wide range of redox potentials (0.5-1.
View Article and Find Full Text PDFActa Biomater
August 2025
Department of Entomology and Nematology, University of Florida, Gainesville, FL, USA.
Transition metals are well known to enrich the cuticle of structural tools among many insect lineages through the formation of metal-ligand coordinated bonds. Investigations that focus on the distribution patterns of metals among different structures, however, are lacking, despite some structural tools hosting different transition metal profiles. Here, we hypothesized that the enrichment of structures with transition metals, including specific metals and their abundances, is contingent on the types of physical forces those structures experience.
View Article and Find Full Text PDFInorg Chem
July 2025
Department of Chemistry, School of Life Sciences, University of Sussex, Brighton BN1 9QJ, U.K.
The oxidation state +2 is of interest in rare-earth chemistry since it allows these conventionally redox-inactive metals to be used as reducing agents. However, the divalent oxidation state is difficult to form for most rare-earth elements, and the ensuing compounds are often unstable. Here, we describe an approach to rare-earth reduction chemistry that circumvents the divalent oxidation state by using compounds of trivalent rare earths that store reducing electrons on the dinitrogen ligand [N], akin to "masked" divalent reactivity.
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