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1. Cyanobacteria from marine oxygen-deficient zones encode both form I and form II Rubiscos

   https://doi.org/10.1073/pnas.2418345121  

   Jaffe, Alexander L; Harrison, Kaitlin; Wang, Renée Z; Taylor-Kearney, Leah J; Jain, Navami; Prywes, Noam; Shih, Patrick M; Young, Jodi; Rocap, Gabrielle; Dekas, Anne E (November 2024, Proceedings of the National Academy of Sciences)

   Cyanobacteria are highly abundant in the marine photic zone and primary drivers of the conversion of inorganic carbon into biomass. To date, all studied cyanobacterial lineages encode carbon fixation machinery relying upon form I Rubiscos within a CO₂-concentrating carboxysome. Here, we report that the uncultivated anoxic marine zone (AMZ) IB lineage of Prochlorococcus from pelagic oxygen-deficient zones (ODZs) harbors both form I and form II Rubiscos, the latter of which are typically noncarboxysomal and possess biochemical properties tuned toward low-oxygen environments. We demonstrate that these cyanobacterial form II enzymes are functional in vitro and were likely acquired from proteobacteria. Metagenomic analysis reveals that AMZ IB are essentially restricted to ODZs in the Eastern Pacific, suggesting that form II acquisition may confer an advantage under low-O₂conditions. AMZ IB populations express both forms of Rubisco in situ, with the highest form II expression at depths where oxygen and light are low, possibly as a mechanism to increase the efficiency of photoautotrophy under energy limitation. Our findings expand the diversity of carbon fixation configurations in the microbial world and may have implications for carbon sequestration in natural and engineered systems. 

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2. Synthesis of Ln ^II ‐in‐Cryptand Complexes by Chemical Reduction of Ln ^III ‐in‐Cryptand Precursors: Isolation of a Nd ^II ‐in‐Cryptand Complex

   https://doi.org/10.1002/anie.202006393  

   Huh, Daniel N.; Ciccone, Sierra R.; Bekoe, Samuel; Roy, Saswata; Ziller, Joseph W.; Furche, Filipp; Evans, William J. (June 2020, Angewandte Chemie International Edition)

   Abstract Lanthanide triflates have been used to incorporate Nd^IIIand Sm^IIIions into the 2.2.2‐cryptand ligand (crypt) to explore their reductive chemistry. The Ln(OTf)₃complexes (Ln=Nd, Sm; OTf=SO₃CF₃) react with crypt in THF to form the THF‐soluble complexes [Ln^III(crypt)(OTf)₂][OTf] with two triflates bound to the metal encapsulated in the crypt. Reduction of these Ln^III‐in‐crypt complexes using KC₈in THF forms the neutral Ln^II‐in‐crypt triflate complexes [Ln^II(crypt)(OTf)₂]. DFT calculations on [Nd^II(crypt)]²⁺], the first Nd^IIcryptand complex, assign a 4f⁴electron configuration to this ion. 

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3. Electrochemical Preparation of Sm(II) Reagent Facilitated by Weakly Coordinating Anions

   https://doi.org/10.1002/chem.202301045  

   Ware, Skyler_D; Zhang, Wendy; Charboneau, David_J; Klein, Channing_K; Reisman, Sarah_E; See, Kimberly_A (July 2023, Chemistry – A European Journal)

   Abstract Samarium diiodide (SmI₂) is widely used as a strong one‐electron reducing agent and is often employed to form C−C bonds in complex systems. Despite their utility, SmI₂and related salts suffer from several drawbacks that render the use of Sm reducing agents in large‐scale synthesis impractical. Here, we report factors influencing the electrochemical reduction of Sm(III) to Sm(II), towards the goal of electrocatalytic Sm(III) reduction. We probe the effect of supporting electrolyte, electrode material, and Sm precursor on Sm(II)/(III) redox and on the reducing power of the Sm species. We find that the coordination strength of the counteranion of the Sm salt affects the reversibility and redox potential of the Sm(II)/(III) couple and establish that the counteranion primarily determines the reducibility of Sm(III). Electrochemically generated SmI₂performs similarly to commercial SmI₂solutions in a proof‐of‐concept reaction. The results will provide fundamental insight to facilitate the development of Sm‐electrocatalytic reactions. 

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4. Diverse Coordination Geometries Derived from Trisaminocyclohexane Ligands with Appended Outer‐Sphere Hydrogen Bond Donors

   https://doi.org/10.1002/ejic.202300434  

   Ekanayake, Danushka_M; Sheridan, Patrick_E; Lindeman, Sergey_V; Fiedler, Adam_T (September 2023, European Journal of Inorganic Chemistry)

   Abstract With the aim of constructing hydrogen‐bonding networks in synthetic complexes, two new ligands derived fromcis,cis‐1,3,5‐triaminocyclohexane (TACH) have been prepared that feature pendant pyrrole or indole rings as outer‐sphere H‐bond donors. The TACH framework offers a facial arrangement of threeN‐donors, thereby mimicking common coordination motifs in the active sites of nonheme Fe and Cu enzymes. X‐ray structural characterization of a series of Cu^I‐X complexes (X=F, Cl, Br, NCS) revealed that these neutral ligands (H₃L^R, R=pyrrole or indole) coordinate in the intended facialN₃manner, yielding four‐coordinate complexes with idealizedC₃symmetry. The N−H units of the outer‐sphere heterocycles form a hydrogen‐bonding cavity around the axial (pseudo)halide ligand, as verified by crystallographic, spectroscopic, and computational analyses. Treatment of H₃L^pyrroleand H₃L^indolewith divalent transition metal chlorides (M^IICl₂, M=Fe, Cu, Zn) causes one heterocycle to deprotonate and coordinate to the M(II) center, giving rise to tetradentate ligands with two remaining outer‐sphere H‐bond donors. Further ligand deprotonation is observed upon reaction with Ni(II) and Cu(II) salts with weakly coordinating counteranions. The reported complexes highlight the versatility of TACH‐based ligands with pendant H‐bond donors, as the resulting scaffolds can support multiple protonation states, coordination geometries, and H‐bonding interactions. 

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5. Probing the Edges between Stability and Degradation of a Series of ZnSe‐Based Layered Hybrid Semiconductors

   https://doi.org/10.1002/admi.202200347  

   Yan, Mengwen; Myers, Christopher_A; John, Gregory_M; Meyers, Vincent_E; Chen, Alan_A; Feldblyum, Jeremy_I (June 2022, Advanced Materials Interfaces)

   Abstract The discovery of layered materials with potentially unique electrical and chemical properties has become a major focus of materials research in the past decade. 2D II–VI layered hybrids (LHs) are a family of ligand‐protected layered materials capable of isolation in few‐layer form and possess emissive and electronic properties of potential relevance to semiconductor device technologies. The authors showed previously that, akin to black phosphorus and transition metal dichalcogenides, 2D II–VI LHs are sensitive to ambient atmospheric conditions. However, the causes for degradation of these ligand‐protected materials remain unclear. Using ZnSe‐based LHs, it is shown herein that the stability of these materials is related to the length and chemistry of the organic ligands coordinated to the LH surfaces. Furthermore, exposure to isotopically enriched H₂¹⁸O and¹⁸O₂reveals that H₂O and O₂are both reactants contributing to ZnSe‐LH degradation. An H₂O‐initiated degradation pathway is proposed and is supported by density functional theory calculations. The findings contribute to the discovery of protection strategies for layered materials and elucidate a degradation pathway that may also be applicable to other layered materials. 

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