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1. Dioxygen Binding Is Controlled by the Protein Environment in Non‐heme Fe ^II and 2‐Oxoglutarate Oxygenases: A Study on Histone Demethylase PHF8 and an Ethylene‐Forming Enzyme

   https://doi.org/10.1002/chem.202300138  

   Chaturvedi, Shobhit_S; Thomas, Midhun_George; Rifayee, Simahudeen_Bathir_Jaber_Sathik; White, Walter; Wildey, Jon; Warner, Cait; Schofield, Christopher_J; Hu, Jian; Hausinger, Robert_P; Karabencheva‐Christova, Tatayana_G; et al (February 2023, Chemistry – A European Journal)

   Abstract This study investigates dioxygen binding and 2‐oxoglutarate (2OG) coordination by two model non‐heme Fe^II/2OG enzymes: a class 7 histone demethylase (PHF8) that catalyzes the hydroxylation of its H3K9me2 histone substrate leading to demethylation reactivity and the ethylene‐forming enzyme (EFE), which catalyzes two competing reactions of ethylene generation and substratel‐Arg hydroxylation. Although both enzymes initially bind 2OG by using anoff‐line2OG coordination mode, in PHF8, the substrate oxidation requires a transition to anin‐linemode, whereas EFE is catalytically productive for ethylene production from 2OG in theoff‐linemode. We used classical molecular dynamics (MD), quantum mechanics/molecular mechanics (QM/MM) MD and QM/MM metadynamics (QM/MM‐MetD) simulations to reveal that it is the dioxygen binding process and, ultimately, the protein environment that control the formation of thein‐lineFe^III‐OO⋅⁻intermediate in PHF8 and theoff‐lineFe^III‐OO⋅⁻intermediate in EFE. 

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2. A High‐Valent Manganese(IV)–Oxo–Cerium(IV) Complex and Its Enhanced Oxidizing Reactivity

   https://doi.org/10.1002/anie.201910032  

   Karmalkar, Deepika G.; Sankaralingam, Muniyandi; Seo, Mi Sook; Ezhov, Roman; Lee, Yong‐Min; Pushkar, Yulia N.; Kim, Won‐Suk; Fukuzumi, Shunichi; Nam, Wonwoo (September 2019, Angewandte Chemie International Edition)

   Abstract A mononuclear nonheme manganese(IV)–oxo complex binding the Ce⁴⁺ion, [(dpaq)Mn^IV(O)]⁺–Ce⁴⁺(1‐Ce⁴⁺), was synthesized by reacting [(dpaq)Mn^III(OH)]⁺(2) with cerium ammonium nitrate (CAN).1‐Ce⁴⁺was characterized using various spectroscopic techniques, such as UV/Vis, EPR, CSI‐MS, resonance Raman, XANES, and EXAFS, showing an Mn−O bond distance of 1.69 Å with a resonance Raman band at 675 cm⁻¹. Electron‐transfer and oxygen atom transfer reactivities of1‐Ce⁴⁺were found to be greater than those of Mn^IV(O) intermediates binding redox‐inactive metal ions (1‐Mⁿ⁺). This study reports the first example of a redox‐active Ce⁴⁺ion‐bound Mn^IV‐oxo complex and its spectroscopic characterization and chemical properties. 

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3. Ynamide and Azaalleneyl. Acid‐Base Promoted Chelotropic and Spin‐State Rearrangements in a Versatile Heterocumulene [(Ad)NCC( ^t Bu)] ⁻

   https://doi.org/10.1002/anie.202401433  

   Russell, John_B; Jafari, Mehrafshan_G; Kim, Jun‐Hyeong; Pudasaini, Bimal; Ozarowski, Andrew; Telser, Joshua; Baik, Mu‐Hyun; Mindiola, Daniel_J (April 2024, Angewandte Chemie International Edition)

   Abstract We introduce the heterocumulene ligand [(Ad)NCC(^tBu)]⁻(Ad=1‐adamantyl (C₁₀H₁₅),^tBu=tert‐butyl, (C₄H₉)), which can adopt two forms, the azaalleneyl and ynamide. This ligand platform can undergo a reversible chelotropic shift using Brønsted acid‐base chemistry, which promotes an unprecedented spin‐state change of the [V^III] ion. These unique scaffolds are prepared via addition of 1‐adamantyl isonitrile (C≡NAd) across the alkylidyne in complexes [(BDI)V≡C^tBu(OTf)] (A) (BDI⁻=ArNC(CH₃)CHC(CH₃)NAr), Ar=2,6‐ⁱPr₂C₆H₃) and [(dBDI)V≡C^tBu(OEt₂)] (B) (dBDI²⁻=ArNC(CH₃)CHC(CH₂)NAr). ComplexAreacts with C≡NAd, to generate the high‐spin [V^III] complex with a κ¹‐N‐ynamide ligand, [(BDI)V{κ¹‐N‐(Ad)NCC(^tBu)}(OTf)] (1). Conversely,Breacts with C≡NAd to generate a low‐spin [V^III] diamagnetic complex having a chelated κ²‐C,N‐azaalleneyl ligand, [(dBDI)V{κ²‐N,C‐(Ad)NCC(^tBu)}] (2). Theoretical studies have been applied to better understand the mechanism of formation of2and the electronic reconfiguration upon structural rearrangement by the alteration of ligand denticity between1and2. 

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4. GLIMPSE: An Ultrafaint ≃10 ⁵ M _⊙ Pop III Galaxy Candidate and First Constraints on the Pop III UV Luminosity Function at z  ≃  6–7

   https://doi.org/10.3847/1538-4357/ade9a1  

   Fujimoto, Seiji; Naidu, Rohan P; Chisholm, John; Atek, Hakim; Endsley, Ryan; Kokorev, Vasily; Furtak, Lukas J; Pan, Richard; Liu, Boyuan; Bromm, Volker; et al (August 2025, The Astrophysical Journal)

   Abstract Detecting the first generation of stars, Population III (Pop III), has been a long-standing goal in astrophysics, yet they remain elusive even in the JWST era. Here we present a novel NIRCam-based selection method for Pop III galaxies, and carefully validate it through completeness and contamination simulations. We systematically search ≃ 500 arcmin²across JWST legacy fields for Pop III candidates, including GLIMPSE, which, assisted by gravitational lensing, has produced JWST’s deepest NIRCam imaging thus far. We discover one promising Pop III galaxy candidate (GLIMPSE-16043) at $z=6.50_{-0.24}^{+0.03}$, a moderately lensed galaxy ( $\mu =2.9_{-0.2}^{+0.1}$) with an intrinsic UV magnitude of $M_{\mathrm{UV}}=-15.89_{-0.14}^{+0.12}$. It exhibits key Pop III features: strong Hαemission (rest-frame EW 2810 ± 550 Å); a Balmer jump; no dust (UV slopeβ = −2.34 ± 0.36); and undetectable metal lines (e.g., [Oiii]; [Oiii]/Hβ < 0.44), implying a gas-phase metallicity ofZ_gas/Z_⊙ < 0.5%. These properties indicate the presence of a nascent, metal-deficient young stellar population (<5 Myr) with a stellar mass of ≃10⁵M_⊙. Intriguingly, this source deviates significantly from the extrapolated UV–metallicity relation derived from recent JWST observations atz= 4–10, consistent with UV enhancement by a top-heavy Pop III initial mass function or the presence of an extremely metal-poor active galactic nucleus. We also derive the first observational constraints on the Pop III UV luminosity function atz ≃ 6–7. The volume density of GLIMPSE-16043 (≈10⁻⁴cMpc⁻³) is in excellent agreement with theoretical predictions, independently reinforcing its plausibility. This study demonstrates the power of our novel NIRCam method to finally reveal distant galaxies even more pristine than the Milky Way’s most metal-poor satellites, thereby promising to bring us closer to the first generation of stars than we have ever been before. 

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5. Unique Dimerization Topology and Countercation Binding Modes in 12‐Metallacrown‐4 Compounds

   https://doi.org/10.1002/ejic.202200439  

   Salerno, Elvin_V; Foley, Collin_M; Marzaroli, Vittoria; Schneider, Bernadette_L; Sharin, Max_D; Kampf, Jeff_W; Marchiò, Luciano; Zeller, Matthias; Guillot, Régis; Mallah, Talal; et al (September 2022, European Journal of Inorganic Chemistry)

   Abstract Seven dimeric metallacrowns (MC) based on Ln[12‐MC_M(III)N(shi)‐4], where Ln^III=Dy, Ho, Yb, or Y, M^III=Mn or Ga, and shi³⁻is salicylhydroximate, have been synthesized and characterized by single‐crystal X‐ray diffraction, and for the dysprosium‐manganese dimers, the magnetic properties have been measured. In each dimer two Ln[12‐MC_M(III)N(shi)‐4] units are linked by four bridging dicarboxylate anions (isophthalate, trimesate, dinicotinate, or 2,2′‐dithiodibenzoate). Three different countercations (sodium, gallium(III), or pyridinium) were used to maintain charge balance of the dimer. While pyridinium does not bind to the dimer, the choice of the dicarboxylate dictates where the countercations Na⁺or Ga^IIIbind. With isophthalate and trimesate, the sodium ion binds to the central MC cavity opposite of the Ln^III, and with dinicotinate the sodium or gallium(III) ions bind to the pyridyl nitrogen of the dinicotinate. All three Dy₂Mn₈dimers exhibit an out‐of‐phase magnetic susceptibility signal consistent with a shallow barrier to magnetization relaxation. 

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