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1. Formation of a Mn ^III –O–Ce ^IV species from a Mn ^III -hydroxo complex and ceric ammonium nitrate

   https://doi.org/10.1039/D5DT01728A  

   Puthiyadath, Anagha; Murphy, Patrick; Mafi, Delara; Patel, Purti; Jackson, Timothy A (September 2025, Dalton Transactions)

   The reaction of a Mn^III-hydroxo complex with ceric ammonium nitrate generates a product with a Mn^III–O–Ce^IVcore that has enhanced reactivity in one-electron oxidation reactions and new reactivity in two-electron oxidation reactions. 

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2. Fine-structure Transitions of Ne ⁺ , Ar ⁺ , Ne ²⁺ , and Ar ²⁺ Induced by Collisions with Atomic Hydrogen

   https://doi.org/10.3847/1538-4357/ad0e77  

   Yan, Pei-Gen; Babb, James F (January 2024, The Astrophysical Journal)

   Abstract We calculate cross sections for fine-structure transitions of Ne⁺, Ar⁺, Ne²⁺, and Ar²⁺in collisions with atomic hydrogen by using quantum-mechanical methods. Relaxation rate coefficients are calculated for temperatures up to 10,000 K. The temperature-dependent critical densities for the relaxation of Ne⁺, Ar⁺, Ne²⁺, and Ar²⁺in collisions with H have been determined and compared to the critical densities for collisions with electrons. The present calculations will be useful for studies utilizing the infrared lines [Neii] 12.8, [Neiii] 15.6, [Neiii] 36.0, [Arii] 6.99, [Ariii] 8.99, and [Ariii] 21.8μm as diagnostics of, for example, planetary nebulae and star formation. 

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3. Spectroscopic Properties and Reactivity of a Mn ^III ‐Hydroperoxo Complex that is Stable at Room Temperature

   https://doi.org/10.1002/chem.202403051  

   Grotemeyer, Elizabeth_N; Aghaei, Zahra; Jackson, Timothy_A (October 2024, Chemistry – A European Journal)

   Abstract Manganese catalysts that activate hydrogen peroxide have seen increased use in organic transformations, such as olefin epoxidation and alkane C−H bond oxidation. Proposed mechanisms for these catalysts involve the formation and activation of Mn^III‐hydroperoxo intermediates. Examples of well‐defined Mn^III‐hydroperoxo complexes are rare, and the properties of these species are often inferred from Mn^III‐alkylperoxo analogues. In this study, we show that the reaction of the Mn^III‐hydroxo complex [Mn^III(OH)(^6Medpaq)]⁺(1) with hydrogen peroxide and acid results in the formation of a dark‐green Mn^III‐hydroperoxo species [Mn^III(OOH)(^6Medpaq)]⁺(2). The formulation of2is based on electronic absorption,¹H NMR, IR, and ESI‐MS data. The thermal decay of2follows a first order process, and variable‐temperature kinetic studies of the decay of2yielded activation parameters that could be compared with those of a Mn^III‐alkylperoxo analogue. Complex2reacts with the hydrogen‐atom donor TEMPOH two‐fold faster than the Mn^III‐hydroxo complex1. Complex2also oxidizes PPh₃, and this Mn^III‐hydroperoxo species is 600‐fold more reactive with this substrate than its Mn^III‐alkylperoxo analogue [Mn^III(OO^tBu)(^6Medpaq)]⁺. DFT and time‐dependent (TD) DFT computations are used to compare the electronic structure of2with similar Mn^III‐hydroperoxo and Mn^III‐alkylperoxo complexes. 

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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. 10 ⁶ -fold faster C–H bond hydroxylation by a Co ^III,IV ₂ (µ-O) ₂ complex [via a Co ^III ₂ (µ-O)(µ-OH) intermediate] versus its Fe ^III Fe ^IV analog

   https://doi.org/10.1073/pnas.2307950120  

   Li, Yan; Abelson, Chase; Que, Lawrence; Wang, Dong (December 2023, Proceedings of the National Academy of Sciences)

   The hydroxylation of C–H bonds can be carried out by the high-valent Co^III,IV₂(µ-O)₂complex2asupported by the tetradentate tris(2-pyridylmethyl)amine ligand via a Co^III₂(µ-O)(µ-OH) intermediate (3a). Complex3acan be independently generated either by H-atom transfer (HAT) in the reaction of2awith phenols as the H-atom donor or protonation of its conjugate base, the Co^III₂(µ-O)₂complex1a. Resonance Raman spectra of these three complexes reveal oxygen-isotope-sensitive vibrations at 560 to 590 cm⁻¹associated with the symmetric Co–O–Co stretching mode of the Co₂O₂diamond core. Together with a Co•••Co distance of 2.78(2) Å previously identified for1aand2aby Extended X-ray Absorption Fine Structure (EXAFS) analysis, these results provide solid evidence for their “diamond core” structural assignments. The independent generation of3aallows us to investigate HAT reactions of2awith phenols in detail, measure the redox potential and pK_aof the system, and calculate the O–H bond strength (D_O–H) of3ato shed light on the C–H bond activation reactivity of2a. Complex3ais found to be able to transfer its hydroxyl ligand onto the trityl radical to form the hydroxylated product, representing a direct experimental observation of such a reaction by a dinuclear cobalt complex. Surprisingly, reactivity comparisons reveal2ato be 10⁶-fold more reactive in oxidizing hydrocarbon C–H bonds than corresponding Fe^III,IV₂(µ-O)₂and Mn^III,IV₂(µ-O)₂analogs, an unexpected outcome that raises the prospects for using Co^III,IV₂(µ-O)₂species to oxidize alkane C–H bonds. 

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