Search Results (77)

Copper(II) coordination complexes with coumarin-derived heterocyclic ligands are promising in inorganic therapeutics for anticancer and antimicrobial applications. To establish quantitative structure–activity relationships for lead design, we studied six copper(II) complexes (Cu1–Cu6)with four- and five-coordinate geometries using Density Functional Theory, Conceptual Density Functional Theory, and visualization analyses. Geometry optimization at M06/6-31G(d)+DZVP revealed distorted coordination environments from $d^9$ Jahn–Teller effects. Tridentate $N_{2}O$-chelatedcomplexes (Cu4–Cu6) showed greater aqueous stability ($\Delta G_{solv}=-43$ to $-50$ kcal·mol⁻¹) than four-coordinate analogs ($-29$ to $-31$ kcal·mol⁻¹). CDFT global descriptors contrasted reactivity: four-coordinate Cu1–Cu2 had higher electron affinity (>4.2 eV) and electrophilicity (>5.7 eV), suggesting propensity for redox cycling and for undergoing nucleophilic attack by DNA bases, whereas Cu4–Cu6 displayed increased chemical hardness (3.43–3.54 eV) and lower electrophilicity (≈3.8 eV), implying enhanced kinetic stability and bioavailability. Frontier orbital analysis indicated ligand-to-metal charge transfer via a LUMO delocalized over the $\pi$-conjugated coumarin, facilitating intercalation by $\pi$-$\pi$ stacking. The visualization showed strong covalent bonds (blue isosurfaces) stabilizing the metal and dispersive $\pi$ interactions (green surfaces) on the ligand, enabling solvent interactions and biomolecular recognition. Tridentate $N_{2}O$ coordination thus balances electronic stability and biological reactivity, making Cu4–Cu6 promising for further study. Full article

A recent theoretical study of CsMnF₄ under pressure presents conclusions on its structural, optical, and magnetic behavior that conflict with established experimental evidence. Crucially, that work omits key prior experimental results on CsMnF₄ and related Mn³⁺ fluorides under pressure. This commentary examines the resulting discrepancies, arguing that omissions of this data undermine the theoretical estimates and methodological validity. This paper provides a critical overview centered on two main points: the contested nature of the pressure-induced high-spin to low-spin transition observed in CsMnF₄ at ~37 GPa, and a detailed discussion of Jahn–Teller physics in this archetypal system. By reconciling the existing literature with the new theoretical claims, this work aims to clarify the high-pressure behavior of CsMnF₄. A thorough analysis on the spectroscopic and magnetic properties of Mn³⁺ fluorides is included to support this commentary. Full article

The development of highly efficient and stable non-noble metal catalysts for volatile organic compound (VOCs) abatement remains a pressing challenge. Mn-based perovskites exhibit superior thermal stability as redox catalysts but suffer from limited activity in light alkane combustion. This study systematically investigates the performance of SmMnO₃ (SMO) perovskite catalysts for propane oxidation through selective etching of Sm species. By precisely controlling the etching process, the removal of surface Sm exposes more active sites and significantly increases the specific surface area from 22.05 m²·g⁻¹ for pristine SMO to 66.15 m²·g⁻¹. SEM and N₂ adsorption–desorption analysis revealed that prolonged etching induces surface roughening and pore channel expansion. XPS and XANES measurements confirmed that an increased Mn⁴⁺/Mn³⁺ ratio enhances reactant adsorption and accessibility to active sites. The etched catalysts exhibited markedly improved activity for propane oxidation, achieving a ~50 °C reduction in light-off temperature compared to the raw SMO. This performance enhancement is attributed to the synergistic effects of enhanced oxygen mobility, elevated Mn⁴⁺ content, and abundant oxygen vacancies. Further characterization via Raman spectroscopy and H₂-TPR revealed weakened Jahn–Teller distortion and lower reduction temperatures, reflecting optimized Mn–O interactions and superior redox properties. Among the samples, SMO-20 demonstrated exceptional stability. Moreover, the SMO-20/cordierite monolithic catalyst maintained outstanding catalytic performance over 1000 h of operation. This work offers a facile and effective approach to engineer perovskite catalysts and provides new insights into structure–activity relationships in VOC oxidation. Full article

The anion, cation, and radical structural forms of B₂N ^(−,0,+) were studied in the case of symmetry breaking (SB) inside a (5, 5) BN nanotube ring and were also compared in terms of non-covalent interaction between these two parts. The non-bonded system of B₂N ^(−,0,+) and the (5, 5) BN nanotube not only causes SB for BNB but also creates an energy barrier in the range of 10⁻³ Hartree of due to this non-bonded interaction. Moreover, several SBs appear via asymmetry stretching and symmetry bending normal mode interactions according to the multiple second-order Jahn–Teller effect. We also demonstrated that the twin minimum of BNB’s potential curve arises from the lack of a proper wave function with permutation symmetry, as well as abnormal charge distribution. Through this investigation, considerable enhancements in the energy barriers due to the SB effect were also observed during the electrostatic interaction of BNB (both radical and cation) with the BN nanotube ring. Additionally, these values were not observed for the isolated B₂N ^(−,0,+) forms. This non-bonded complex operates as a quantum rotatory model and as a catalyst for producing a range of spectra in the IR region due to the alternative attraction and repulsion forces. Full article

This paper studies the formation process of a composite material based on an organic substance, biochar from sunflower husks, and an inorganic substance, nickel (II)-copper (II) ferrites of the composition Cu_xNi_1−xFe₂O₄ (x = 0.0; 0.5; 1.0). The obtained materials were characterized by X-ray phase analysis, scanning electron microscopy, and FTIR spectroscopy. It is shown that when replacing copper (II) cations with nickel (II) cations, the average parameters and volume of the unit cell gradually decrease, and the cation–anion distances in both the tetrahedral and octahedral spinel grids also decrease with regularity. The oxide materials were found to form a film on the surface of biochar, repeating its porous structure. The obtained materials exhibit high catalytic activity in the methyl orange decomposition reaction under the action of hydrogen peroxide in an acidic medium; the degradation of methyl orange in an aqueous solution occurs 30 min after the start of the reaction. This result may be associated with the formation of the Fenton system during the oxidation–reduction process. A significant increase in the reaction rate in the system containing mixed nickel–copper ferrite as a catalyst may be associated with the formation of a more defective structure due to the Jahn–Teller effect manifestation, which creates additional active centers on the catalyst surface. Full article

Cd-based perovskite materials have the advantages of high emission efficiency and tunable emission, as well as broad application prospects in the field of optoelectronics. However, achieving multimode dynamic luminescence under UV light excitation in a single system is a great challenge. Here, we successfully prepared Sb³⁺/Pb²⁺ co-doped Cs₇Cd₃Br₁₃ crystals by a simple hydrothermal method. Tunable emission from orange to white and then to blue, covering the wavelength range between 370 and 800 nm, was achieved by varying the doping concentration of Pb²⁺ ions in Cs₇Cd₃Br₁₃:0.5%Sb³⁺. Temperature-dependent photoluminescence (PL) spectra and density functional theory (DFT) calculations confirm that the wide-band white-light emission of Cs₇Cd₃Br₁₃: Sb³⁺/Pb²⁺ crystal comes from the first self-trapped exciton (STE1) of undoped Cs₇Cd₃Br₁₃ intrinsic capture state and the emission of free excitons (FEs) and STE2 induced by the confining effect and the Jahn–Teller effect by Pb²⁺ incorporation, as well as the Sb triplet self-trapped exciton (STE3). More specifically, the samples with the best co-doped ratio exhibit significant excitation-wavelength-dependent luminescence characteristics and can realize the conversion of the emission color from white and blue to orange. Based on the tunable emission characteristics of three emission colors, the material has good prospects in encryption and anti-counterfeiting applications. This work provides a new strategy for the application of Cd-based halides in the field of anti-counterfeiting. Full article

In this study, 3-chlorothiophene-2-carboxylic acid (HL) was used as a main ligand to successfully synthesize four novel complexes: [Cu(L)₂(Py)₂(OH₂)₂] (1), [Co(L)₂(Py)₂(OH₂)₂] (2) (Py = pyridine), [{Ni(L)₂(OH₂)₄}₂{Ni(L)(OH₂)₅}]L•5H₂O (3), and [{Co(L)₂(OH₂)₄}₂{Co(L)(OH₂)₅}]L•5H₂O (4). All four compounds were identified by elemental analysis and ESI mass spectrometry, and subsequently characterized by IR spectroscopy, UV-visible diffuse reflectance spectroscopy, electron paramagnetic resonance spectroscopy, thermogravimetric analysis, single-crystal X-ray crystallography, and cyclic voltammetry. X-ray analyses revealed that complexes 1 and 2 exhibit a centrosymmetric pseudo-octahedral coordination geometry; the copper (II) and cobalt (II) metal ions, respectively, are located at the crystallographic center of inversion. The coordination sphere of the copper (II) complex is axially elongated in accordance with the Jahn–Teller effect. Intriguingly, for charge neutrality, compounds 3 and 4 crystallized as three independent mononuclear octahedrally coordinated metal centers, which are two $\left[\mathrm{M}{\mathrm{L}}_2{\left({\mathrm{O}\mathrm{H}}_2\right)}_4\right]$ complex molecules and one ${\left[\mathrm{M}\mathrm{L}{\left({\mathrm{O}\mathrm{H}}_2\right)}_5\right]}^{+}$ complex cation (M = ${\mathrm{N}\mathrm{i}}^{\mathrm{I}\mathrm{I}}$ and ${\mathrm{C}\mathrm{o}}^{\mathrm{I}\mathrm{I}}$, respectively), with the ligand anion ${\mathrm{L}}^{-}$ serving as the counter ion. The anticancer activities of these complexes were systematically assessed on human leukemia K562 cells, lung cancer A549 cells, liver cancer HepG2 cells, breast cancer MDA-MB-231 cells, and colon cancer SW480 cells. Among them, complex 4 shows significant inhibitory effects on leukemia K562 cells and colon cancer SW480 cells. Full article

Manganese oxides (MnO_x) have been confirmed as the most promising candidates for aqueous zinc-ion batteries (AZIBs) due to their cost-effectiveness, high theoretical capacity, high voltage platforms, and environmental friendliness. However, in practical applications, AZIBs are hindered by the Jahn–Teller distortion (JTD) effect, primarily induced by Mn³⁺ (t_2g³e_g¹) in octahedral coordination, which leads to severe structural deformation, rapid capacity fading, and poor cycling stability. This review systematically outlines the fundamental mechanisms of JTD in MnO_x cathodes, including electronic structure changes, lattice distortions, and their side effects on Zn²⁺ storage performance. Furthermore, we critically discuss advanced strategies to suppress JTD, such as cation/anion doping, interlayer engineering, surface/interface modification, and electrolyte optimization, aimed at enhancing both structural stability and electrochemical performance. Finally, we propose future research directions, such as in situ characterization, machine learning-guided material design, and multifunctional interfacial engineering, to guide the design of high-performance MnO_x hosts for next-generation AZIBs. This review may provide a promising guideline for overcoming JTD challenges and advancing MnO_x-based energy storage systems. Full article

Layered transition metal oxide (LTMO) cathode materials for sodium-ion batteries (SIBs) have attracted extensive attention due to their unique structural stability and excellent electrochemical performance. However, their poor stability in air has significantly impeded their practical application, as exposure to moisture and carbon dioxide can lead to Na⁺ loss, phase transitions, and decreased electrochemical performance. This paper reviews the application of high-entropy strategies in sodium-ion LTMO cathode materials, focusing on the optimization of air stability and electrochemical performance through approaches including high-entropy cation regulation, P2/O3 dual-phase synergistic structures, and fluorine ion doping. Studies have shown that high-entropy design can effectively inhibit phase transitions, alleviate Jahn–Teller distortion, enhance oxygen framework stability, and markedly enhance the cycle life and rate performance of materials. Furthermore, future research directions are proposed, including the use of advanced characterization techniques to reveal failure mechanisms, the integration of machine learning to optimize material design, and the development of high-performance mixed-phase structures. High-entropy strategies provide new perspectives for the development of SIBs cathode materials with enhanced air stability, potentially promoting the practical application of SIBs in large-scale energy storage systems. Full article

Cu-based layered double hydroxides (LDH) have been extensively employed as catalyst precursors. However, due to the Jahn–Teller effect of copper ions, it is a challenge to synthesize well-crystallized LDH with a high Cu content, which usually contains considerable CuO impurity. By adding competitive ligands during the coprecipitation process, such as glycine, a well-crystallized Cu-rich LDH with less CuO impurity was successfully synthesized. The Cu-Mg-Al mixed oxides derived from the well-crystallized Cu-rich LDH have relatively high S_BET, large pore volume, and well dispersion of Cu nanoparticles. The derived catalyst exhibited unexpectedly high catalytic activity in the water–gas shift (WGS) reaction, and the mass-specific reaction rate was reached as high as 33.5 μmol_CO${·\mathrm{g}}_{\mathrm{cat}}^{-1}$·s⁻¹ at 200 °C. The high catalytic activity of this catalyst may originate from the high S_BET and well dispersion of Cu particles and metal oxides. Moreover, the derived catalyst also displayed outstanding long-term stability in the WGS reaction, which should benefit from the enhanced metal–support interaction. Full article

Tunnel-structured Na_0.44MnO₂ (NMO) has been extensively studied as a potential cathode for sodium-ion batteries (SIBs) due to its favorable cycling endurance, cost-effectiveness, environmental benignity, and notable air-moisture stability. However, limitations, such as sluggish ion diffusion kinetics, an insufficient Na⁺ storage capacity, and an unsatisfactory Jahn–Teller effect, impede its widespread application. To address these problems, this study proposes a co-doping strategy that involves the simultaneous introduction of a cation and an anion. The optimized cathode Na_0.44Mn_0.99Ni_0.01O_1.985F_0.015 demonstrates remarkable rate capabilities with average discharge capacities of 136.2, 133.0, 129.6, 124.0, 115.9, and 95.8 mAh g⁻¹ under current rates ranging from 0.1 to 5 C. Furthermore, it also exhibits exceptional long-term cyclability, retaining 86.5% and 89.4% capacity retention at 1 and 5 C after 200 and 400 cycles, respectively, accompanied by nearly 100% Coulombic efficiency. A comprehensive structural characterization and experimental analysis reveal that the synergistic incorporation of Ni and F can effectively adjust the lattice parameters and alleviate the Jahn–Teller distortion of the NMO cathode, thereby resulting in enhanced structural integrity, rapid ion transfer dynamics, and excellent sodium storage performance. Consequently, this investigation establishes a significant approach for optimizing tunnel-phase Mn-based cathodes through the synergistic effect of cation and anion co-doping, which promotes the practical implementation of advanced SIBs. Full article

Na₄Fe₃(PO₄)₂P₂O₇ (NFPP) is recognized as a prospective electrode for sodium-ion batteries (SIBs) because of its structure stability, economic viability and environmental friendliness. Nevertheless, its commercialization is constrained by low operating voltage and limited theoretical capacity, which result in a power density significantly inferior to that of LiFePO₄. To address these limitations, in this work, we first designed and synthesized a series of Mn-doped NFPP to enhance its operating voltage, inspired by the successful design of LiFe_1-xMn_xPO₄ cathodes. This approach was implemented to enhance the operating voltage of the material. Subsequently, the optimized Na₄Fe_1.2Mn_1.8(PO₄)₂P₂O₇ (1.8Mn-NFMPP) sample was selected for further Ti-doped modification to enhance its cycle durability and rate performance. The final Mn/Ti co-doped Na₄Fe_1.2Mn_1.7Ti_0.1(PO₄)₂P₂O₇ (0.1Ti-NFMTPP) material exhibited a high operating voltage of ~3.6 V (vs. Na⁺/Na) in a half cell, with an outstanding reversible capacity of 122.9 mAh g⁻¹ at 0.1 C and remained at 90.6% capacity retention after 100 cycles at 0.5 C. When assembled into a coin-type full cell employing a commercial hard carbon anode, the optimized cathode material exhibited an initial capacity of 101.7 mAh g⁻¹, retaining 86.9% capacity retention over 50 cycles at 0.1 C. These results illustrated that optimal Mn/Ti co-doping is an effective methodology to boost the electrochemical behavior of NFPP materials, achieving mitigation of the Jahn–Teller effect on the Mn³⁺ and Mn dissolution problem, thereby significantly improving structural stability and cycling performance. Full article

The organic–inorganic hybrid (BEDT-TTF)₃[Cu₂(μ-C₂O₄)₃·CH₃CH₂OH·1.2H₂O] (I) was obtained using the electrocrystallization method. It comprises a θ²¹-phase organic donor layer and a two-dimensional inorganic antiferromagnetic honeycomb lattice. Cu(II) is octahedrally coordinated by three bisbidenetate oxalates, exhibiting Jahn–Teller distortion. CH₃CH₂OH and H₂O molecules are located within the cavities of the honeycomb lattice. The total formal charge of the three donor molecules was assigned to be +2 based on the bond lengths in the TTF core, which corresponded to the Raman spectra. It is a semiconductor with σ_rt = 0.04 S/cm and E_α = 40 meV. No long-range ordering was observed above 2 K from zero-field cooling/field cooling magnetization, as confirmed by specific heat measurements. The spin frustration with f > 10 from the antiferromagnetic copper-oxalate-framework was observed. It is a candidate quantum spin liquid. Full article

Early on, oxides were ruled out from superconductivity, since they are typically large-band-gap insulators. Nevertheless, a rather small number of them were found to be superconducting, with transition temperatures up to 14 K and a remarkably low carrier density. This was the starting point of K. Alex Müller (KAM) becoming interested in superconductivity in oxides. Step by step, he advanced the research on oxides and finally discovered, together with J. Georg Bednorz, high-temperature superconductivity (HTSC) in the perovskite-type compound Ba-La-Cu-O. Even though he was inspired by specific and clear ideas in his search, he added new impact in the understanding of HTSC for many years after receipt of the Nobel prize for this discovery. Full article

The P2-Na_0.7MnO_2.05 cathode material has long been constrained by phase transitions induced by the Jahn–Teller (J–T) effect during charge–discharge cycles, leading to suboptimal electrochemical performance. In this study, we employed a liquid phase co-precipitation method to incorporate Ti during the precursor Mn₃O₄ synthesis, followed by calcination to obtain Na_0.7Ti_xMn_(1−x)O_2.05 materials. We investigated the effects of Ti doping on the structure, morphology, Mn³⁺ concentration, and Na⁺ diffusion coefficients of Na_0.7Ti_xMn_(1−x)O_2.05. Our findings revealed that the 7% Ti-doped NTMO-007 sample exhibited reduced grain agglomeration and smaller particle sizes compared to the undoped sample, thereby enhancing the electrode–electrolyte contact area and electrochemical activity. Additionally, Ti doping increased the crystal cell volume of Na_0.7MnO_2.05 and broadened the Na⁺ transport channels, significantly enhancing the Na⁺ diffusion coefficient. At a 0.5 C rate, the NTMO-007 sample demonstrated a specific capacity of 143.3 mAh g⁻¹ with an 81.8% capacity retention after 100 cycles, markedly outperforming the undoped NMO sample, which had a capacity retention of only 61.5%. Full article