Dalton Transactions最新文献

The supply of battery-grade nickel to produce positive electrodes of sodium-ion batteries may soon become insufficient. For this reason, it is crucial to find new electrode materials that minimize its use or even fully remove this element from synthesis. We have prepared a Na_0.67Mg_0.05Fe_xNi_yMn_zO₂ (0 ≤ x ≤ 0.2; y = 0.05, 0.15; 0.6 ≤ z ≤ 0.9) series with low Ni and Fe contents by a single and easily scalable sol–gel method. This procedure yields high-purity and crystalline samples as evidenced by structural, morphological, and spectroscopic studies, including X-ray diffraction, electron microscopy, and X-ray photoelectron spectroscopy. The electrochemical tests showed an exceptional performance for the F0N05 sample with the lowest (Ni + Fe) contents, at 5 C (ca. 100 mA h g⁻¹), and good capacity retention after 100 cycles. This excellent behaviour was also evidenced when cycling at −15 °C. These results were confirmed by electrochemical techniques, such as cyclic voltammetry and impedance spectroscopy, that evidenced a fast exchange of sodium ions due to a significant capacitive contribution and high apparent diffusion coefficients. Post-mortem analysis of the F0N05 electrodes by XRD showed the reversible insertion and the absence of detrimental P2–O2 and P2–P2′ transitions, while XPS spectra demonstrated the reversible redox activity of both transition metals and oxygen.

Two new selenites, K₂Zn₃Se₄O₁₂ (compound 1) and K₄Zn₃V₄Se₂O₁₉ (compound 2), have been successfully synthesized by solid-state reactions in vacuum tubes. Compound 1 consists of a three-dimensional (3D) framework with [SeO₃] triangular pyramids and [ZnO₄] tetrahedra in the monoclinic space group P2₁/c (No. 14). Compound 1′s cut-off edge is below 344 nm, based on its UV-Vis-NIR diffuse reflectance studies, and theoretical calculations indicate a birefringence of around 0.043 at 1064 nm. The two-dimensional layer of compound 2, in contrast, is made up of [SeO₃] triangular pyramids, [ZnO₄] tetrahedra, and [V₄O₁₃] tetrahedra. It crystallizes in the monoclinic space group C2/c (No. 15). Its UV-Vis-NIR diffuse reflectance studies demonstrate that the compound's cut-off edge is lower than 330 nm.

The first alkaline-earth metal thioborate–thiophosphate Ba₃(BS₃)(PS₄) was designed from Ba₃(BO₃)(PO₄) by S–O substitution and fabricated experimentally. The [BS₃] pseudo-layers formed in the structure contribute to the strong optical anisotropy and a large birefringence of ∼0.11 at 1064 nm. The results enrich the structural and chemical diversity of chalcogenides.

Eighteen mononuclear copper(II) complexes with oxygen-containing N4O1 pentadentate ligands were prepared. The ligand library consists of 2-aminoethanol derivatives ((Ar¹CH₂)(Ar²CH₂)NCH₂CH₂OCH₂Ar³) bearing three nitrogen-containing heteroaromatics (Ars) including pyridine, quinoline and isoquinoline via a methylene linker. Systematic replacements of pyridine binding sites with quinolines and isoquinolines reveal the general trends in the perturbation of bond distances and angles, the redox potential and the absorption maximum wavelength of the copper(II) complexes, depending on the position and number of (iso)quinoline heteroaromatics. The small effect on the redox potentials resulting from quinoline substitution at the Ar³ position (near oxygen) of the ligand comes from the steric hindrance of the peri hydrogen atom in the quinoline moiety at this position, which removes the counter anion to enhance the coordination of quinoline nitrogen and ether oxygen atoms to the metal centre. In the absorption spectra of copper(II) complexes in the d–d transition region, the quinoline substitution at this site (Ar³) exhibits an opposite effect to those at the Ar¹ and Ar² sites. The electronic and steric contributions of the heteroaromatic binding sites to the ligand properties are comprehensively discussed.

The crystallization of ZrSiO₄ is generally accomplished by the addition of mineralizers into ZrO₂–SiO₂ binary oxides. The current investigation aimed to investigate the effect of adding calcium phosphates into ZrO₂–SiO₂ binary oxides on the yield of ZrSiO₄. The concentration of calcium phosphate additions were varied to obtain ZrSiO₄ that fetches improved mechanical and biological properties for application in hard tissue replacements. The findings highlight the significant role of Ca²⁺ and P⁵⁺ in triggering the ZrSiO₄ formation via their accommodation at the Zr⁴⁺ and Si⁴⁺ sites. Especially, calcium phosphate additions trigger the t- → m-ZrO₂ transition beyond 1000 °C, which consequently reacts with SiO₂ to promote ZrSiO₄ formation. Calcium phosphates are accommodated at the lattice sites of ZrSiO₄ with a maximum limit of 20 mol%, beyond which the crystallization of β-Ca₃(PO₄)₂ is noticed. The optimum amount of 20 mol% of calcium phosphates displayed a better strength than that of all the investigated specimens. More than 80% of cell viability in MG-63 cells was invariably determined in all the calcium phosphate-added ZrSiO₄ systems.

With the exceptional advantages of safety, greenness, and low cost, photocatalytic H₂O₂ generation has kindled a wonderful spark, although being severely hampered by the terrible photoinduced exciton recombination, migration, and surface decomposition. Here, employing reflux method, the Cd–Mo–Se quantum dots of varying molar ratios of Cd and Mo were synthesized using thioglycolic acid as the capping ligand to regulate their growth. This type of metal alloying promotes rapid charge migration, improves light harvesting, and reduces the rate of charge recombination. The improved optoelectronic properties and boosted activity of Cd-rich ternary CMSe-1 QDs led to the observed exceptional photocatalytic H₂O₂ yield of 1403.5 μmol g⁻¹ h⁻¹ (solar to chemical conversion efficiency, 0.27%) under visible light, outperforming the other ternary and Se-based QD photocatalysts. Additionally, CMSe-1 shows 93.6% (2 h) hazardous Cr(VI) photoreduction. The enhanced catalytic performance of CMSe-1 corresponds to effective charge carrier separation and transfer efficiency, well supported by PL, TRPL, and electrochemical measurements. Photocatalytic H₂O₂ production was also studied under varying experimental conditions and the scavenger test suggests a superoxide radical intermediate 2-step single electron reduction pathway. The catalyst-assisted Cr(VI) reduction is substantiated by the zero-order kinetics as well as the determination of the pH_PZC value. The catalyst can be employed for a maximum of four times while retaining its activity, according to the photostability and reusability test outcomes. This research presents interesting approaches for producing ternary QDs and modified systems for efficient photocatalytic H₂O₂ production and Cr(VI) reduction.

Incorporating catalytic units into a crystalline porous matrix represents a facile way to build high-efficiency heterogeneous catalysts, and by rational design of the porous skeleton with appropriate building blocks the catalytic performance can be significantly enhanced for a series of organic transformations owing to the synergistic effect from the multicomponent and confined porous microenvironment around catalytically active sites. Herein, we demonstrate that the design and synthesis of a porous polyoxometalate-based metal–organic framework YL₂(H₂O)₂[CrMo₆O₁₈(PET)₂]·4H₂O (POMOF-1) constructed from Anderson-type [CrMo₆O₁₈(PET)₂] (PET = pentaerythritol), which can be employed as a multifunctional platform for synthesis of N-containing compounds via selective oxidative coupling with amines. POMOF-1 features microporous 1D channels defined by Y³⁺ and L, with [CrMo₆O₁₈(PET)₂] arranged orderly between adjacent Lvia electrostatic interactions. Upon using POMOF-1 as a catalyst and H₂O₂ as an oxidant, a variety of amines could be effectively converted to value-added amides, imines and azobenzenes via the oxidative cross-coupling with alcohols or homo-coupling. In particular, POMOF-1 showed dramatically improved activity for the N-formylation reaction owing to the synergistic and confinement effect, with the yield of amides up to 95% and 4 times higher than that of homogeneous [CrMo₆O₁₈(PET)₂]. Meanwhile, the oxidative homo-coupling of arylmethylamines and arylamines can be facilely tuned by adjustment of the amount of oxidant, solvent and additive, affording imines and azobenzenes in high selectivity and yield, respectively. POMOF-1 is robust and can be reused for 5 cycles with little loss of catalytic activity and structural integrity. The work demonstrates that the combination of catalytically active POMs with crystalline porous MOFs holds great potential to build robust and recyclable heterogeneous systems with enhanced activity and selectivity for multifunctional catalysis.

One hexa- and two octanuclear Cu(II) complexes were synthesised from different metal salts and a very large (8 + 8) tetraeicosaaza macrocycle. These nitrate, chloride and sulphate coordination compounds were characterised by taking elemental analysis, spectroscopy, crystallography and magnetic susceptibility measurements. Their crystal structures revealed different interesting coordination modes of Cu(II) cations and nuclearity in these centrosymmetric complexes. For the sulphate complex two different, homo- vs. heterochiral, arrangements of the same macrocycle L3 around the same Cu(II) cations take place.

In this study, a series of Al complexes bearing amidates, thioamidates, ureidates, and thioureidates were synthesized and their catalytic activity for ε-caprolactone (CL) polymerization was evaluated. S^Pr-Al exhibited a higher catalytic activity than O^Pr-Al (3.2 times as high for CL polymerization; [CL] : [S^Pr-Al] : [BnOH] = 100 : 0.5 : 2; [S^Pr-Al] = 10 mM, conv. = 93% after 14 min at 25 °C), and US^Cl-Al exhibited a higher catalytic activity than U^Cl-Al (4.6 times as high for CL polymerization; [CL] : [US^Cl-Al] : [BnOH] = 100 : 0.5 : 2; [US^Cl-Al] = 10 mM, conv. = 90% after 15 min at 25 °C). Regardless of whether aluminum amidates or ureidates were present, thioligands improved the polymerization rate of aluminum catalysts. Density functional theory calculations revealed that the eight-membered ring [S^Pr-AlOMe₂]₂ decomposed into the four-membered ring S^Pr-AlOMe₂. However, [O^Pr-AlOMe₂]₂ did not decompose because of its strong bridging Al–O bond. The overall activation energy required for CL polymerization was lower when using [S^Pr-AlOMe₂]₂ (18.1 kcal mol⁻¹) as a catalyst than when using [O^Pr-AlOMe₂]₂ (23.9 kcal mol⁻¹). This is because the TS2a transition state of S^Pr-AlOMe₂ had a more open coordination geometry with a small N–Al–S angle (72.91°) than did TS3c of [O^Pr-AlOMe₂]₂, the crowded highest-energy transition state of [O^Pr-AlOMe₂]₂ with a larger N–Al–O angle (99.63°).

The catalytic activity of a transition metal (host) oxide can be influenced by doping with a second cation (dopant), but the key factors dominating the activity of the doped catalyst are still controversial. Herein, CeO₂ doped with Ni, Mn, and Y catalysts prepared using aerosol pyrolysis were used to demonstrate the positive, negative, and additive effects on CO oxidation as a model reaction. Various characterization results indicated that Ni, Mn, and Y had been successfully doped into the CeO₂ lattice. The catalytic activities of each catalyst for CO conversion were in the order of Ni–CeO₂ > Mn–CeO₂ > CeO₂ > Y–CeO₂. Operando DRIFTS-MS and various characterization methods were applied to reveal the intrinsic nature of the doping effects. The accumulation rate of the surface bidentate carbonates determined the CO oxidation. A definition to evaluate the doping effect was proposed, which is anticipated to be useful for developing a rational catalyst with a high CO oxidation activity. The CO oxidation reactivities displayed strong correlations with the surface factors obtained from operando DRIFTS-MS analysis and the structure factors from XPS and Raman analyses.