Chemistry - A European Journal最新文献

Controlling bistable spin states in Fe(II) spin-crossover (SCO) frameworks remains challenging. Here, we demonstrate that guest-induced chemical pressure provides a reversible and general strategy to amplify thermal hysteresis. In the flexible Hofmann-type MOF [Fe(pz)Pd(CN)₄], vapor-phase iodine uptake produces a record-wide thermal hysteresis of 120 K, far exceeding previously reported values. Structural and magnetic analyses confirm that the framework remains intact, and lattice compression by iodine enhances cooperative spin transitions, stabilizing both high-spin and low-spin (LS) states. Partial iodine loading induces multistep SCO with asymmetric hysteresis, whereas full saturation generates extreme bistability with symmetric hysteresis. This approach establishes guest capture as a direct, reversible tool to control SCO bistability, offering a broadly applicable design principle for multifunctional porous materials.

This study successfully fabricated a freestanding ZnO@(NiFe)OOH nano-heterostructure array electrocatalyst with high hydrophilicity for efficient electrocatalytic nitrate reduction to ammonia (NO₃RR) in neutral media. The material integrates the large specific surface area of one-dimensional ZnO nanoarrays with the electronic modulation capability of heterogeneous interfaces, which significantly enhances nitrate adsorption and activation, promotes proton supply, and effectively suppresses the hydrogen evolution side reaction. The highly hydrophilic surface further accelerates electrolyte diffusion, nitrate ion transport, and product desorption. In a neutral electrolyte of 0.1 M PBS containing 0.15 M KNO₃ at a potential of -1.0 V (vs. RHE), the catalyst achieves an ammonia production rate of 4.86 mg·h^-1·cm^-2 with a Faradaic efficiency of 85.58%, while generating minimal byproducts, demonstrating excellent catalytic selectivity and stability. This work provides a new strategy for the structural design and performance enhancement of NO₃RR electrocatalysts, which holds significance for advancing green ammonia synthesis and enabling efficient conversion of nitrate in water pollution control.

Hexanuclear cyclic Gd(III) coordination compounds are promising candidates for magnetic and magnetocaloric applications, yet systematic series remain rare due to synthetic challenges. We report the synthesis and characterization of five new complexes with the general formula [Gd(H₃bt)(carboxylate)]₆, employing four different carboxylate coligands. Single‑crystal X‑ray diffraction confirmed their isostructural nature, with polymorphism observed in the 4‑bromobenzoate derivatives. Magnetic properties were investigated using SQUID magnetometry and complemented by Broken Symmetry DFT calculations. The study reveals weak antiferromagnetic exchange interactions and notable magnetocaloric performance, with entropy changes approaching 28 J K^{- 1} kg^{- 1} at 2.7 K (other compounds measured at 2 K) and 9 T. Magneto‑structural correlations based on structural parameters and substituent effects were established, providing guidelines for tuning exchange interactions in cyclic Gd(III) systems. Incorporation of a thioether substituent further suggests potential for surface deposition, opening pathways toward device‑oriented applications.

Sodium-ion batteries (SIBs) have garnered significant attention in the field of large-scale energy storage due to their abundant sodium resources, low cost, and similar working principles to lithium-ion batteries. The cathode material is a pivotal component that governs the overall energy density and cost structure of SIBs. NASICON-type Na₃MnTi(PO₄)₃ (NMTP) only contains high abundance elements and allows large capacity with high working voltage based on multi-electron redox reactions, which makes NMTP become a great potential cathode material for SIBs. However, NMTP suffers from serious voltage hysteresis mainly caused by electronic-conductivity limits and intrinsic structural defects, deteriorating its available electrochemical performance. In this review, we overview recent insights into mechanisms of voltage hysteresis and modification strategies of NMTP cathodes. Surface carbon coating can only improve apparent electronic conductivity, but metal ion doping is the most effective strategy to suppress intrinsic Mn/Na anti-site defects (IASD) thus alleviating voltage hysteresis. By comprehensive consideration of solid solubility, valence state, and electronegativity of dopants, we propose a guiding rule for future doping strategies to reduce IASD and suppress voltage hysteresis of NMTP. We hope that this review can provide some insights into the development of NMTP and other NASICON-type phosphate cathode materials.

Here, we describe a novel titanocene-catalyzed synthesis of functionalized dihydroquinazolinones by an intramolecular radical addition to quinazolinones. The mechanistic key-issue is the reduction of the radical σ-complex formed after the addition of the epoxide-derived β-titanoxy radical that is unprecedented in titanocene-catalyzed radical arylations. The diastereoselectivity of product formation is high, and a number of functional groups are tolerated in the pharmaceutically relevant 6- and 7-positions of the dihydroquinazolinone products. If desired, these products can be oxidized to the corresponding quinazolinones with MnO₂.

Some peptide sequences are known to interact with their enantiomers to form stereocomplexes. However, the sequence-dependent conditions required for stereocomplexation have not been thoroughly elucidated. Here, we present a systematic investigation of peptide stereocomplexation using short tripeptides and their enantiomers. Stereocomplexation was evaluated by aggregate formation in mixed aqueous solutions, and single-crystal X-ray diffraction revealed racemic crystals. Stereocomplexation was driven by hydrophobic interactions between phenylalanine residues and electrostatic interactions involving lysine and the C-terminus. Thermodynamic and structural features of the complexation were further elucidated by calorimetry, simulations, and fluorescence assays. On the basis of these insights, a D-peptide (Ac-fffakr5-NH₂) was rationally designed to target the -FFAE- motif of amyloid β42 (Aβ42), a pathological intrinsically disordered protein. This D-peptide inhibited the fibrillization and cytotoxicity of Aβ42 in neuronal-like cells, outperforming a clinical candidate, peptide drug RD2. These findings establish peptide stereocomplexation as a viable strategy for constructing sequence-targeting ligands even against intrinsically disordered proteins.

Biomass-derived carbon-based composites, renowned for their extensive sources, low cost, low density, and unique pore structure, have garnered increasing attention as electromagnetic wave (EMW) absorbers. In this work, tangerine peel featuring a natural honeycomb porous structure was selected as the precursor to construct honeycomb porous carbon/Fe/Fe₄N triphasic composites (Fe/Fe₄N/PC) via facile freeze-drying and nitridation procedures. Specifically, the nitridation process under an NH₃ atmosphere facilitates the in situ formation of Fe₄N magnetic nanoparticles through the reaction between Fe and N species. The synergistic integration of the honeycomb porous structure, Fe/Fe₄N magnetic particles, and biomass-derived carbon enriches the electromagnetic loss mechanisms, encompassing conduction loss, dipole polarization, magnetic loss, and multiple reflections. Consequently, the Fe/Fe₄N/PC composites exhibit exceptional EMW absorption performance: the minimum reflection loss (RL_{m i n}) reaches -55.93 dB at a thickness of 2.6 mm, and the maximum effective absorption bandwidth (EAB) achieves 5.41 GHz at 1.7 mm. Additionally, radar cross section (RCS) simulation results demonstrate that the Fe/Fe₄N/PC composite prominently reduces the RCS signal by 42.6 dB·m² at 16°, confirming its superior practical stealth potential. This study provides insightful guidance for the design and eco-friendly fabrication of honeycomb porous structured absorbers, offering a strategy for developing high-performance and sustainable EMW absorbers.

Localized surface plasmon resonance (LSPR) is widely applied in photo-functional technologies such as photocatalysis and solar cells. Semiconductor nanoparticles (NPs) have recently become a target for LSPR materials research due to the fact that their composition and structure flexibility allow for the fine-tuning of optical properties. However, due to the difficulty of controlling the crystal structure of NPs, many of the crystallographic factors governing the LSPR of semiconductor NPs are not understood. Here, we report on the crystal structure and size-controlled synthesis of CuGaS₂ (CGS) NPs, which are typical I-III-VI₂ semiconductors. Moreover, we investigate their LSPR properties and reveal the crystal structure dependence of LSPR extinction. We show that chalcopyrite and wurtzite CGS (c-CGS and w-CGS, respectively) dictate LSPR in the NIR region. Moreover, the extinction coefficient of c-CGS was approximately 3 times larger than that of w-CGS, which we explain in terms of the larger polarizability of c-CGS. These results deepen our understanding of semiconductor plasmonics and may serve as a foundation for developing highly efficient energy conversion systems.

Biomass-based hard carbons are particularly attractive as the anode materials for Na-ion batteries due to their tunable microstructure, suitable operating potential, and cost effectiveness. Nevertheless, the complex biomass composition makes the precise tailoring of internal carbon microstructure challenging for boosted Na-ion storage. In this work, we develop a compositional engineering strategy to tailor the pseudographitic structure of hard carbon by deep eutectic solvent. The green solvent selectively dissolves low-crystalline compositions (hemicellulose, lignin, and amorphous cellulose), and the remaining crystalline cellulose facilitates the construction of desired pseudo-graphitic domains with expanded carbon interlayer spacing and abundant ultramicro/closed pores. Consequently, the as-tailored cotton-derived hard carbon delivers an enhanced capacity of 318 mAh g^-1 at 20 mA g^-1 and an impressive initial Coulombic efficiency of 85%. Additionally, the anode can sustain good sodium storage performance at low temperatures and in full cells. This study demonstrates an eco-friendly and effective strategy for fabricating high-performance biomass-based hard carbons and accelerating the development of Na-ion technology.

High-resolution nuclear magnetic resonance (NMR) spectroscopy is essential for molecular characterization at atomic resolution in chemical research. Here we report and justify the experimental setup to be followed when data acquisition occurs in solution at elevated hydrostatic pressure of up to thousands of bars. We demonstrate how the compressibility of the solvent can be reliably and accurately determined by combining resonance signals originating from six different isotopes using pressure-resistant molecules. The knowledge of solvent compression is then used for the precise quantification of changes in free energy and volume of a biomolecule that are caused by increasing hydrostatic pressure. Our data show that solvent compression must be considered when conducting quantitative analyses of data obtained with NMR spectroscopy at high hydrostatic pressure.