Chemistry - A European Journal最新文献

Ligand design plays a crucial role in developing chiral transition metal complexes with enhanced or new catalytic properties. Here, we report our progress toward a new class of linear tetradentate NCCN ligands incorporating strongly σ-donating carbene moieties. The NCCN ligand coordinates to iron(II) in a cis-α topology, with two pyridine donors occupying the apical positions and two 1,2,3-triazolin-5-ylidene mesoionic carbene (MIC) donors in the equatorial plane. Two acetonitrile ligands complete the octahedral coordination sphere, and their lability provides the basis for the observed catalytic activity. Notably, the two strongly σ-donating MIC groups create a strong ligand field, which is critical for achieving configurational stability of the metal-centered stereogenicity. This design strategy thus enabled the first chiral-at-iron catalyst derived from an achiral tetradentate ligand, which was applied to catalytic and enantioselective C(sp³)-H amination and a Cannizzaro reaction.

Polyethylene and polystyrene are among the most representative hard-to-degrade plastic due to their chemical inertness and massive generation, making their efficient upcycling a pressing challenge for environmental sustainability. Conventional recycling methods, such as incineration, landfilling, and mechanical processing, often cause high energy consumption, severe pollution, and product devaluation, which is unfavorable for circular utilization of plastics. In contrast, chemical recycling, particularly catalytic oxidation, has recently gained much attention for enabling plastic valorization under relatively mild conditions, with straightforward separation processes and high-value products. Despite these advantages, catalytic oxidation remains at an early stage, facing challenges such as unclear catalyst structure-activity relationships, insufficient reactivity, and limited selectivity. To address these issues, this review highlights recent advances in the catalytic oxidative conversion of polyethylene and polystyrene, focusing on catalyst design, reaction mechanism elucidation, and product selectivity control. Furthermore, perspectives are provided on future research directions, including the development of novel catalysts, optimization of mass transfer, regulation of reactive oxygen species, adaptability to mixed plastic waste, techno-economic analysis, life cycle assessment, and reaction safety evaluation.

Low-pressure chemical vapor deposition (CVD) offers good scalability, substrate compatibility, and solvent-free processing for metal halide perovskite films fabrication, yet limited control over the film composition has hindered the device performance compared to solution-based methods. Herein, we investigate how the substrate surface property affect the composition and optoelectronic properties of perovskite films fabricated by CVD. By changing the hole transporting layers (HTLs), different crystallization process and chemical stoichiometry of perovskite films have been observed. Perovskite films grown on nickel oxide|self-assembled monolayers (SAMs) exhibit a more stoichiometric buried surface, along with a higher work function (WF) and enhanced p-type character that are favorable for hole transport. Leveraging these insights, we demonstrate all vapor-deposited semitransparent perovskite solar cells (ST-PSCs) with a champion efficiency of 18.0%, retaining ∼100% of the initial performance after 500 h of continuous operation (ISOS-L-1). Furthermore, we achieve a champion efficiency of 17.5% for semitransparent mini-modules fabricated via the all-vacuum process.

Chirality transfer and amplification are prevailing in biological systems, which play vital roles in the homochirality of life. Systems with remote chirality transfer and amplification remain actively pursued, aiming to construct novel chiral materials for advanced applications. Chiral supramolecular assembly stands out as a promising way to construct molecular assemblies through multiple synergistic noncovalent interactions, which enable the construction of various chiral materials. Here, we have developed a novel chiral monomer that was able to self-assemble in nonpolar solvents and afforded chiral fibers. The self-assembly process was found to be tuned by solvent composition and concentration. The self-assembly kinetics were affected by solvents and concentrations as well. The chirality can be transferred from the remote chiral center at the peripheries of the compound to the center of the molecule and was amplified during the self-assembly process via helical stacking of the adjacent monomers. Furthermore, CPL and energy transfer relay systems were also successfully realized with the chiral self-assemblies.

Layered double hydroxides (LDHs) are low-cost and versatile materials, many of which are well-established water oxidation electrocatalysts. A simple MgFe-LDH variant, synthesized as size-tunable nanosheets, was successfully decorated on the surface of hematite (α-Fe₂O₃) nanorods to structure an integrating photoanode for improved photoelectrochemical (PEC) water oxidation. Combined XPS and SEM analysis showed that MgFe-LDH decoration does not interfere with the nanostructure of the light-harvesting α-Fe₂O₃. However, intensified Raman bands for the decorated α-Fe₂O₃ pointed to enhanced interactions between MgFe-LDH and α-Fe₂O₃. Optimization of the surface amount for MgFe-LDH can lead to a 340 mV cathodic shift in the onset potential at 0.1 mA cm^-2. Mott-Schottky analysis and electrochemical impedance spectroscopy further revealed that LDH decoration enhances the photogenerated charge-carrier separation and efficiently consumes holes accumulating at the electrode surface. Furthermore, density functional theory (DFT) calculations suggest a lower Gibbs free energy (ΔG) value of 1.35 eV for MgFe-LDH/α-Fe₂O₃ contrasted to pristine α-Fe₂O₃ (ΔG of 1.46 eV) for the rate-determining step (RDS), further indicating that the MgFe-LDH co-catalyst lowers the activation energy barrier for the OER. This work offers a promising method for designing high-efficiency and low-cost hematite-based photoanodes for solar-fuel devices relying on noncritical elements.

Although transition-metal-catalyzed asymmetric benzylic substitution is conceptually analogous to asymmetric allylic substitution, proceeding via η³-benzyl-metal and η³-allyl-metal intermediates, respectively, the development of the former, involving benzylic electrophiles, has received comparatively less attention within the synthetic community. This limited progress is largely attributed to the low reactivity of benzylic electrophiles and the associated challenge in achieving stereoselective control. Over the past several decades, different catalytic strategies, such as single metal catalysis, bimetallic catalysis, metal/organo catalysis, and ternary catalysis, have been developed to address these challenges. Asymmetric versions of these transformations have also been established, enabling the construction of stereocenters either at the benzylic electrophiles, at nucleophile, or simultaneously at both sites. This review provides a comprehensive overview of this field from its inception to the present. It summarizes advances in substrate scope, mechanistic understanding, synthetic applications, and remaining challenges, with the aim of fostering further progress in this emerging area.

We present a new organocatalytic method for synthesizing aldehydes under mild conditions using readily accessible terminal epoxides as starting materials and bis(trifluoromethane)sulfonimide (Tf2NH) as the catalyst. We identified intermediate aldehyde dimerization products at lower temperatures and observed their cleavage at 55°C. We isolated the products in yields of 89-97% using catalyst loadings as low as 0.5 mol%. To underline the applicability of our new approach, we synthesized ibuprofen in a three-step process and overall yield of 90%.

Molecular recognition is a crucial process in multiple areas, including separation, storage, and catalysis etc. Covalent organic cages (COCs), owing to their preorganized 3D cavities, customizable binding sites, and outstanding chemical stability, have been widely used for molecular recognition. Among the components of COCs, the covalent linkers play a crucial role in molecular recognition by shaping cavities and providing noncovalent interactions. In this concept, we exemplified recent progress in COC-based host-guest recognition, briefly summarized the bonding strategies (both dynamic and irreversible) used in covalent linkers for COC construction, and discussed how these linkers influence guest encapsulation by adjusting size, shape, and binding sites of their cavities. These insights are expected to provide a reference for the design of novel COCs for molecular recognition.

This review covers the reactivity of cyclopropenes under light irradiation. Cyclopropenes have a formidable and complex photochemistry. While fundamental photochemistry of cyclopropenes was early studied, the synthetic potential has not been developed at comparable pace as synthetic photochemistry has recently evolved. In this review, the main types of light-mediated reactivity of cyclopropenes is briefly presented and focus on the synthetic possibilities offered by these reactions. Moreover, photochemical reactions in which cyclopropenes at ground state react with other photo-excited molecules are also presented. Finally, the value of cyclopropenes in a different field as light-mediated bio-orthogonal reactions is succinctly introduced.

The mechanism of O-O bond formation in PSII is still debated. Although it is generally accepted to occur during the S₃ → [S₄] → S₀ transition, some studies suggest it may already begin in the S₃ state. Notably, the 2017 XFEL study by Suga et al. supports this hypothesis by reporting structural features consistent with a peroxide intermediate formed from the S₃ state. Here, we present DFT calculations showing that, in the high oxidation state (HOS) model, O-O coupling starting from the S₃ state with the hydroxo-oxo configuration is kinetically feasible, forming a peroxide intermediate via a modest activation energy of 19.5 kcal/mol. However, in the HOS model, the resulting peroxide would be readily converted to O₂ with ΔG^‡ = 11 kcal mol^-1, inconsistent with experimental observations that O₂ release proceeds only after reaching the [S₄] state. In contrast, we show that if peroxide forms from the S₃ state, its persistence is more plausibly explained by the low oxidation state (LOS) model, where further conversion to superoxide or O₂ is energetically unfavorable. This distinction between these two models stems from the greater oxidizing power of Mn(IV) in the HOS paradigm relative to Mn(III) in the LOS paradigm in promoting peroxide-to-O₂ conversion.