Hydrogen Treatment for Superparamagnetic VO2 Nanowires with Large Room‐Temperature Magnetoresistance

One‐dimensional (1D) transition metal oxide (TMO) nanostructures are actively pursued in spintronic devices owing to their nontrivial d electron magnetism and confined electron transport pathways. However, for TMOs, the realization of 1D structures with long‐range magnetic order to achieve a sensitive magnetoelectric response near room temperature has been a longstanding challenge. Herein, we exploit a chemical hydric effect to regulate the spin structure of 1D V–V atomic chains in monoclinic VO₂ nanowires. Hydrogen treatment introduced V³⁺ (3d²) ions into the 1D zigzag V–V chains, triggering the formation of ferromagnetically coupled V³⁺–V⁴⁺ dimers to produce 1D superparamagnetic chains and achieve large room‐temperature negative magnetoresistance (?23.9 %, 300 K, 0.5 T). This approach offers new opportunities to regulate the spin structure of 1D nanostructures to control the intrinsic magnetoelectric properties of spintronic materials.     

Realignment of Nanocrystal Aggregates into Single Crystals as a Result of Inherent Surface Stress

Crystallization by particle attachment is widely observed in both natural and synthetic environments. Although this form of nonclassical crystallization is generally described by oriented attachment, random aggregation of building blocks to give single‐crystal products is also observed, but the mechanism of crystallographic realignment is unknown. We herein reveal that random attachment during aggregation‐based growth initially produces a nonoriented growth front. Subsequent evolution of the orientation is driven by the inherent surface stress applied by the disordered surface layer and results in single‐crystal formation by grain‐boundary migration. This mechanism is corroborated by measurements of orientation rate versus external stress, which demonstrated a predictive relationship between the two. These findings advance our understandings about aggregation‐based growth via nanocrystal blocks and suggest an approach to material synthesis that takes advantage of stress‐induced coalignment.     

Direct Hydrogenation of Dinitrogen and Dioxygen via Eley–Rideal Reactions

Most Eley–Rideal abstraction reactions involve an energetic gas‐phase atom reacting directly with a surface adsorbate to form a molecular product. Molecular projectiles are generally less reactive, may dissociate upon collision with the surface, and thus more difficult to prove that they can participate intact in abstraction reactions. Here we provide experimental evidence for direct reactions occurring between molecular N₂⁺ and O₂⁺ projectiles and surface‐adsorbed D atoms in two steps: first, the two atoms of the diatomic molecule undergo consecutive collisions with a metal surface atom without bond rupture; and second, the rebounding molecule abstracts a surface D atom to form N₂D and O₂D intermediates, respectively, detected as ions. The kinematics of the collisional interaction confirms product formation by an Eley–Rideal reaction mechanism and accounts for inelastic energy losses commensurate with surface re‐ionization. Such energetic hydrogenation of dinitrogen may provide facile activation of its triple bond as a first step towards bond cleavage.     

Lanthanide‐Catalyzed Reversible Alkynyl Exchange by Carbon–Carbon Single‐Bond Cleavage Assisted by a Secondary Amino Group

Lanthanide‐catalyzed alkynyl exchange through C?C single‐bond cleavage assisted by a secondary amino group is reported. A lanthanide amido complex is proposed as a key intermediate, which undergoes unprecedented reversible β‐alkynyl elimination followed by alkynyl exchange and imine reinsertion. The in situ homo‐ and cross‐dimerization of the liberated alkyne can serve as an additional driving force to shift the metathesis equilibrium to completion. This reaction is formally complementary to conventional alkyne metathesis and allows the selective transformation of internal propargylamines into those bearing different substituents on the alkyne terminus in moderate to excellent yields under operationally simple reaction conditions.     

Accelerated Chemical Reactions and Organic Synthesis in Leidenfrost Droplets

Leidenfrost levitated droplets can be used to accelerate chemical reactions in processes that appear similar to reaction acceleration in charged microdroplets produced by electrospray ionization. Reaction acceleration in Leidenfrost droplets is demonstrated for a base‐catalyzed Claisen–Schmidt condensation, hydrazone formation from precharged and neutral ketones, and for the Katritzky pyrylium into pyridinium conversion under various reaction conditions. Comparisons with bulk reactions gave intermediate acceleration factors (2–50). By keeping the volume of the Leidenfrost droplets constant, it was shown that interfacial effects contribute to acceleration; this was confirmed by decreased reaction rates in the presence of a surfactant. The ability to multiplex Leidenfrost microreactors, to extract product into an immiscible solvent during reaction, and to use Leidenfrost droplets as reaction vessels to synthesize milligram quantities of product is also demonstrated.     

A Programmable Signaling Molecular Recognition Nanocavity Prepared by Molecular Imprinting and Post‐Imprinting Modifications

Inspired by biosystems, a process is proposed for preparing next‐generation artificial polymer receptors with molecular recognition abilities capable of programmable site‐directed modification following construction of nanocavities to provide multi‐functionality. The proposed strategy involves strictly regulated multi‐step chemical modifications: 1) fabrication of scaffolds by molecular imprinting for use as molecular recognition fields possessing reactive sites for further modifications at pre‐determined positions, and 2) conjugation of appropriate functional groups with the reactive sites by post‐imprinting modifications to develop programmed functionalizations designed prior to polymerization, allowing independent introduction of multiple functional groups. The proposed strategy holds promise as a reliable, affordable, and versatile approach, facilitating the emergence of polymer‐based artificial antibodies bearing desirable functions that are beyond those of natural antibodies.     

Proton‐Coupled Reduction of an Iron Cyanide Complex to Methane and Ammonia

Nitrogenase enzymes mediate the six‐electron reductive cleavage of cyanide to CH₄ and NH₃. Herein we demonstrate for the first time the liberation of CH₄ and NH₃ from a well‐defined iron cyanide coordination complex, [SiP^iPr₃]Fe(CN) (where [SiP^iPr₃] represents a tris(phosphine)silyl ligand), on exposure to proton and electron equivalents. [SiP^iPr₃]Fe(CN) additionally serves as a useful entry point to rare examples of terminally‐bound Fe(CNH) and Fe(CNH₂) species that, in accord with preliminary mechanistic studies, are plausible intermediates of the cyanide reductive protonation to generate CH₄ and NH₃. Comparative studies with a related [SiP^iPr₃]Fe(CNMe₂) complex suggests the possibility of multiple, competing mechanisms for cyanide activation and reduction.