An Open-Shell Fe Nitrido.

We report the photogeneration and characterization of an open-shell, terminal iron nitrido (L)Fe(N) using a sterically encumbered dipyrrin ligand environment. The Fe-N distance in the solid-state, zero-field Fe Mössbauer spectrum, and computational analysis are consistent with a triplet electronic ground state of the iron nitrido. Notably, the attenuation of Fe-N multiple bond character through occupying π* enables (i) primary C(sp)-H amination, (ii) H cleavage, (iii) aromatic C-C cleavage, and (iv) photocatalytic -atom transfer reactivity.

Self-assembly of chiroptical ionic co-crystals from silver nanoclusters and organic macrocycles.

Atomically precise nanoclusters can be assembled into ordered superlattices with unique electronic, magnetic, optical and catalytic properties. The co-crystallization of nanoclusters with functional organic molecules provides opportunities to access an even wider range of structures and properties, but can be challenging to control synthetically. Here we introduce a supramolecular approach to direct the assembly of atomically precise silver nanoclusters into a series of nanocluster‒organic ionic co-crystals with tunable structures and properties.

Composition Determination of Heterometallic Trinuclear Clusters via Anomalous X-ray and Neutron Diffraction.

Anomalous X-ray diffraction (AXD) and neutron diffraction can be used to crystallographically distinguish between metals of similar electron density. Despite the use of AXD for structural characterization in mixed metal clusters, there are no benchmark studies evaluating the accuracy of AXD toward assessing elemental occupancy in molecules with comparisons with what is determined via neutron diffraction. We collected resonant diffraction data on several homo and heterometallic clusters and refined their anomalous scattering components to determine metal site occupancies.

C-H Insertion from Isolable Copper Benzylidenes.

Despite the utility of copper catalysts for the insertion of carbene moieties into C-H bonds, the copper carbene intermediate often invoked in these transformations has not been isolated. Herein, we describe the synthesis and structural characterization of a series of copper benzylidenes utilizing the sterically encumbered dipyrrin ligand (L)H. These isolated copper carbenes demonstrate intramolecular insertion into the primary C(sp)-H bond of the ligand (L)H and intermolecular insertion into ethereal and allylic C-H bonds.

Photoredox Oxidation of Alkanes by Monometallic Copper-Oxygen Complexes Using Visible Light Including One Sun Illumination.

Oxygenation of hydrocarbons offers versatile catalytic routes to more valuable compounds, such as alcohols, aldehydes, and ketones. Despite the importance of monometallic copper-oxygen species as hydroxylating agents in biology, few synthetic model compounds are known to react with hydrocarbons, owing to high C-H bond dissociation energies. To overcome this challenge, the photoredox chemistry of monometallic copper (pyrazolyl)borate complexes coordinated by chlorate has been explored in the presence of C-C alkanes with BDEs ≥ 93 kcal/mol.

High-Spin [Fe] Cluster Capable of Pnictogen Atom Capture.

Using a new hexanucleating anildophosphine ligand LH (1,3,5-CH(NHCH-5-F-2-P(Bu))), the all-monovalent [Fe] compound (L)Fe () was isolated and characterized by X-ray diffraction analysis, SQUID magnetometry, Fe Mössbauer spectroscopy, and cyclic voltammetry. The molecular structure of reveals very close Fe-Fe distances of 2.3825(7), 2.

Cluster dynamics of heterometallic trinuclear clusters during ligand substitution, redox chemistry, and group transfer processes.

Stepwise metalation of the hexadentate ligand LH (LH = 1,3,5-CH(NHCH--NHSiMeBu)) affords bimetallic trinuclear clusters (L)FeZn(thf) and (L)FeZn(py). Reactivity studies were pursued to understand metal atom lability as the clusters undergo ligand substitution, redox chemistry, and group transfer processes. Chloride addition to (L)FeZn(thf) resulted in a mixture of species including both all-zinc and all-iron products.

Hierarchical Self-Assembly of Multidimensional Functional Materials from Sequence-Defined Peptoids.

Hierarchical self-assembly represents a powerful strategy for the fabrication of functional materials across various length scales. However, achieving precise formation of functional hierarchical assemblies remains a significant challenge and requires a profound understanding of molecular assembly interactions. In this study, we present a molecular-level understanding of the hierarchical assembly of sequence-defined peptoids into multidimensional functional materials, including twisted nanotube bundles serving as a highly efficient artificial light harvesting system.

Oxygen quenching of structurally characterized [5,10,15,20-tetrakis(4-fluoro-2,6-dimethylphenyl)porphyrinato]platinum(II).

The compound [5,10,15,20-tetrakis(4-fluoro-2,6-dimethylphenyl)porphyrinato]platinum(II), [Pt(CHFN)] or Pt(II)TFP, has been synthesized and structurally characterized by single-crystal X-ray crystallography. The Pt porphyrin exhibits a long-lived phosphorescent excited state (τ = 66 µs), which has been characterized by transient absorption and emission spectroscopy. The phosphorescence is extremely sensitive to oxygen, as reflected by a quenching rate constant of 5.

The role of metal accessibility on carbon dioxide electroreduction in atomically precise nanoclusters.

Atomically precise nanoclusters (NCs) can be designed with high faradaic efficiency for the electrochemical reduction of CO to CO (FE) and provide useful model systems for studying the metal-catalysed CO reduction reaction (CORR). While size-dependent trends are commonly evoked, the effect of NC size on catalytic activity is often convoluted by other factors such as changes to surface structure, ligand density, and electronic structure, which makes it challenging to establish rigorous structure-property relationships. Herein, we report a detailed investigation of a series of NCs [AuAg(C[triple bond, length as m-dash]CR)Cl(PPh), AuAg(C[triple bond, length as m-dash]CR)Cl, and Au(C[triple bond, length as m-dash]CR)/AuAg(C[triple bond, length as m-dash]CR)] with similar sizes and core structures but different ligand packing densities to investigate how the number of accessible metal sites impacts CORR activity and selectivity.

Lewis Acid Supported Nickel Nitrenoids.

Metalation of the polynucleating ligand LH (1,3,5-C H (NC H -4-F-2-NSiMe Bu) ) with two equivalents of Zn(N(SiMe ) ) affords the dinuclear product ( LH )Zn (1), which can be further deprotonated to yield ( L)Zn Li (OEt ) (2). Transmetalation of 2 with NiCl (py) yields the heterometallic, trinuclear cluster ( L)Zn Ni(py) (3). Reduction of 3 with KC affords [KC ][( L)Zn Ni] (4) which features a monovalent Ni centre.

Nitrene transfer from a sterically confined copper nitrenoid dipyrrin complex.

Despite the myriad Cu-catalyzed nitrene transfer methodologies to form new C-N bonds (, amination, aziridination), the critical reaction intermediates have largely eluded direct characterization due to their inherent reactivity. Herein, we report the synthesis of dipyrrin-supported Cu nitrenoid adducts, investigate their spectroscopic features, and probe their nitrene transfer chemistry through detailed mechanistic analyses. Treatment of the dipyrrin Cu complexes with substituted organoazides affords terminally ligated organoazide adducts with minimal activation of the azide unit as evidenced by vibrational spectroscopy and single crystal X-ray diffraction.

Structure-Property Optimization of a Series of Imidazopyridines for Visceral Leishmaniasis.

Leishmaniasis is a collection of diseases caused by more than 20 parasite species that manifest as either visceral, cutaneous, or mucocutaneous leishmaniasis. Despite the significant mortality and morbidity associated with leishmaniasis, it remains a neglected tropical disease. Existing treatments have variable efficacy, significant toxicity, rising resistance, and limited oral bioavailability, which necessitates the development of novel and affordable therapeutics.

A Double Open-Shelled Au Nanocluster with Increased Catalytic Activity and Stability.

Atomically precise metal nanoclusters (NCs) are an intriguing class of crystalline solids with unique physicochemical properties derived from tunable structures and compositions. Most atomically precise NCs require closed-shells and coordinatively saturated surface metals in order to be stable. Herein, we report Au(C≡CBu) and AuAg(C≡CBu), which feature open electronic and geometric shells, leading to both paramagnetism (23 valence e) and enhanced catalytic activity from a single coordinatively unsaturated surface metal.

Crystal structure of a methyl benzoate quadruple-bonded dimolybdenum complex.

Quadruple-bond dimolybdenum complexes provide invaluable insight into the two-electron bond, with structural chemistry providing a foundation for examination of bond properties. The synthesis and solid-state structure of the quadruple-bonded dimolybdenum(II) complex tetra-kis-(-4-methyl-benzoato- :')bis[(tetra-hydro-furan-κ)molybdenum(II)] tetra-hydro-furan disolvate, [Mo(CHO)(CHO)]·2CHO, are presented. This complex crystallizes in a triclinic cell with low-symmetry space group .

Chemical Stability of Petrichorins.

The structure of petrichorin C1 () converted from petrichorin C () was determined using NMR spectroscopy and X-ray crystallography. The chemical stability of petrichorins A and C ( and ) was investigated by NMR spectroscopy, X-ray crystallography, and calculations.

Potent Uncompetitive Inhibitors of Nicotinamide -Methyltransferase (NNMT) as In Vivo Chemical Probes.

NNMT uses SAM as a cofactor to catalyze the methylation of nicotinamide, producing 1-methylnicotinamide. Recent studies have shown that NNMT upregulation in cancer-associated fibroblasts (CAFs) is required to maintain the CAF phenotype in high-grade serous carcinoma. These observations suggest that NNMT should be evaluated as a therapeutic target, especially in cancer.

Syntheses and Properties of Metalated Tetradehydrocorrins.

The monoanionic tetrapyrrolic macrocycle ,-tetradehydrocorrin (TDC) resides chemically between corroles and corrins. This chemical space remains largely unexplored due to a lack of reliable synthetic strategies. We now report the preparation and characterization of Co(II)- and Ni(II)-metalated TDC derivatives ( and , respectively) with a combination of crystallographic, electrochemical, computational, and spectroscopic techniques.

Highly Selective -Alkylation of Pyrazoles: Crystal Structure Evidence for Attractive Interactions.

Inspired by crystal structures, we designed and achieved a catalyst-free Michael reaction for the preparation of an N1-alkyl pyrazole in a high yield (>90%) with excellent regioselectivity (N1/N2 > 99.9:1). The scope of this protocol has been extended to accomplish the first general regioselective N1-alkylation of 1-pyrazoles to give di-, tri-, and tetra-substituted pyrazoles in a single step.

Colossal barocaloric effects with ultralow hysteresis in two-dimensional metal-halide perovskites.

Pressure-induced thermal changes in solids-barocaloric effects-can be used to drive cooling cycles that offer a promising alternative to traditional vapor-compression technologies. Efficient barocaloric cooling requires materials that undergo reversible phase transitions with large entropy changes, high sensitivity to hydrostatic pressure, and minimal hysteresis, the combination of which has been challenging to achieve in existing barocaloric materials. Here, we report a new mechanism for achieving colossal barocaloric effects that leverages the large volume and conformational entropy changes of hydrocarbon order-disorder transitions within the organic bilayers of select two-dimensional metal-halide perovskites.

Proton-coupled electron transfer of macrocyclic ring hydrogenation: The chlorinphlorin.

SignificanceThe chemical reduction of unsaturated bonds occurs by hydrogenation with H as the reductant. Conversely, in biology, the unavailability of H engenders the typical reduction of unsaturated bonds with electrons and protons from different cofactors, requiring olefin hydrogenation to occur by proton-coupled electron transfer (PCET). Moreover, the redox noninnocence of tetrapyrrole macrocycles furnishes unusual PCET intermediates, including the phlorin, which is an intermediate in tetrapyrrole ring reductions.

Selective electrochemical capture and release of uranyl from aqueous alkali, lanthanide, and actinide mixtures using redox-switchable carboranes.

We report the selective electrochemical biphasic capture of the uranyl cation (UO ) from mixed-metal alkali (Cs), lanthanide (Nd, Sm), and actinide (Th, UO ) aqueous solutions to an organic, 1,2-dichloroethane (DCE), phase using the -substituted -carborane anion, [1,2-(PhPO)-1,2-CBH] (Cb). The reduced Cb is generated by electrochemical reduction of the -carborane, Cb, prior to mixing with the aqueous mixed-metal solution. Subsequent UO release from the captured product, [UO(Cb)], was performed by galvanostatic bulk electrolysis of the DCE phase and back-extraction of UO to a fresh aqueous phase.

Synthesis, Characterization, and Hydrogen Evolution Activity of Metallo--(4-fluoro-2,6-dimethylphenyl)porphyrin Derivatives.

Zn(II), Cu(II), and Ni(II) 5,10,15,20-tetrakis(4-fluoro-2,6-dimethylphenyl)porphyrins (TFPs) have been synthesized and characterized. The electronic spectroscopy and cyclic voltammetry of these compounds, along with the free-base macrocycle (2H-TFP), have been determined; 2H-TFP was also structurally characterized by X-ray crystallography. The Cu(II)TFP exhibits catalytic activity for the hydrogen evolution reaction (HER).

Crystal structure of a tri-fluoro-methyl benzoato quadruple-bonded dimolybdenum complex.

The study of quadruple bonds between transition metals, in particular those of dimolybdenum, has revealed much about the two-electron bond. The solid-state structure of the quadruple-bonded dimolybdenum(II) complex tetra-kis-[μ-4-(tri-fluoro-methyl)-benzoato-κ :']bis[(tetra-hydro-furan-κ)molybdenum(II)] 0.762-pentane 0.

Teaching space-group diagrams to chemistry students through a peer-tutoring approach.

Peer tutoring is a teaching strategy that offers a creative way of getting students more involved and accountable for their own learning in college-level chemistry courses. The authors have found that the '' [Jasinski & Foxman (2007). , V1.