Transition Metal Chemistry最新文献

Among the various peroxides that are available, meta-chloroperbenzoic acid (mCPBA) is an effective oxidizing reagent that is used in a variety of oxidative transformations, including rearrangements, oxidation of different functional groups, and the formation of carbon–carbon and carbon–heteroatom bonds. This mini-review aims to emphasize on properties, structures, and reactivities of intermediate species involved in the representative metal-assisted contributions of mCPBA in organic synthesis and catalysis along with its scope, merits, and demerits of the reaction from mid-2015 to date.

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The effects of mechanical activation on the characteristics of copper and synthesized silver-coated copper powders were investigated. The characterization was carried out using particle size analysis, XRD, BET, SEM, AAS, EDS-map analyses, and electrical resistivity measurements. The obtained results showed that d80 of copper powder changes from 60 to 200 µm as the milling time increases from 0 to 1 h. Meanwhile, by expanding the milling time to more than 2 h, the d80 of the powders decreased to about 50 µm. The specific surface area of copper powder increased from 0.04 to 0.21 m²/g for milling duration of 0.5–1 h. The specific surface area reached to a maximum value of 0.3 m²/g for the milling duration of 16 h. Morphological examination of the core–shell particles produced from 4 to 16 h ball-milled copper powder revealed that surface of the copper particles is completely covered with silver. Studies showed that the apparent density of the samples prepared from Cu–Ag core–shell powder and copper powder decreased from 7.2 to 5.8 g/cm³ and from 6.2 to 5.8 g/cm³, respectively, by increasing the ball milling time from 0 to 16 h. The electrical resistivity of the core–shell bulk samples is always constant (0.25 Ω-cm), but the resistivity of copper bulk samples increased (1–5 Ω-cm) with longer milling time (0–16 h).

A novel two-dimensional coordination polymer {[Co(Htia)₂(C₂H₅OH)₂]·H₂O}_n (1) (H₂tia = 5-(1H-1,2,4-triazol-1-yl)isophthalic acid, C₁₀N₃O₄H₇) was successfully synthesized by a solvothermal method using H₂tia containing –COOH and –N bifunctional groups as ligands and transition metal Co as the central ion. 1 was analyzed by XRD, IR, UV and TG. Single-crystal X-ray diffraction analysis shows that Co²⁺ ions in 1 are the hexagonal distorted octahedral geometry. Neighboring Co²⁺ ions form a two-dimensional grid using the Htia ligand as the rigid skeleton. The adjacent 2D layers interact through hydrogen bonds to build a three-dimensional supramolecular crystalline material. Based on the laminar structure of 1, we investigated the adsorption capacity of 1 on two cationic dyes, crystalline violet and Janus green B. The results show that 1 has a certain adsorption capacity and the maximum adsorption amount of the dyes can reach as high as 56 and 176 mg g⁻¹, respectively. The electrochemical experiment shows that 1 has good electrocatalytic activity in the electrolyte solution of 0.01 M KOH not only for the oxidation of H₂O₂, but also for the oxidation of ascorbic acid.

In this paper, three complexes La₂(thd)₆ (thd = 2,2,6,6-tetramethyl-3,5-heptanedione, 1)_, La₂(tmod)₆ (tmod = 2,2,6,6-tetramethyl octane-3, 5-dionates, 2) and La₂(ibpm)₆ (ibpm = 2,2,6-trimethyl-3, 5-heptane-dionates, 3) were synthesized by one-step method and characterized with ¹H-NMR, ¹³C-NMR and X-ray single-crystal diffraction. The melting point and TGA data demonstrated that the asymmetry of the ligand and the number of flexible joints could improve the volatility of the complex. With the help of asymmetry and flexible joint, La₂(tmod)₆ was selected as ALD precursor to deposit La₂O₃ film on SiO₂/Si (100) wafer. The self-limited deposition results demonstrated that La₂(tmod)₆ is better precursor than reported La₂(thd)₆ and La(thd)₃-DMEA (DMEA = N,N-dimethylethylenediamine).

Titanium dioxide (TiO₂) can only be stimulated by UV light, making its real application for photocatalytic water treatments ineffective, particularly under sunlight and visible light irradiation. As a result, significant efforts have been conducted over the last decades to fabricate visible light-active TiO₂ photocatalysts through band-gap engineering. Herein, nitrogen-doped titanium dioxide (N-TiO₂) photocatalysts were effectively prepared by utilizing a simple sol–gel process with ethanol as a single solvent and urea as the nitrogen source under ambient temperature and pressure. The effects of urea concentration (0, 2, 4, 6 urea/TTIP mol ratio) on the optical, structural, morphological, and photocatalytic properties of the photocatalysts were investigated. SEM morphology revealed an aggregated nano-spherical shape in all samples. HR-TEM and SAED patterns showed an anatase phase of 2-N-TiO₂. The X-ray diffraction analysis also showed a pure anatase phase for pure TiO₂, 2-N-TiO₂, and 4-N-TiO₂. However, the crystalline phase transformed to amorphous for 6-N-TiO₂. The crystallite size reduced from 14.16 to 9.76 nm upon increasing urea concentration. The band-gap energy of N-TiO₂ also decreased from 3.25 to 2.95 eV. Furthermore, the photocatalytic experiment was examined for the degradation of colorless and colored pollutants, such as salicylic acid (SA), methyl blue (MB), and rhodamine B (RhB). The results showed the photocatalytic activity of 2-N-TiO₂ exhibited an optimum efficiency compared to the 4-N-TiO₂ and 6-N-TiO₂, for photocatalytic degradation of SA (k = 0.0265 min⁻¹), MB (k = 0.0180 min⁻¹) and RhB (k = 0.1071 min⁻¹), under visible light irradiation. Therefore, the results suggest that crystallite size, urea (as an N dopant) concentration, and organic model pollutants were critical parameters for the photocatalytic activity of N-TiO₂ under visible irradiation.

The water pollution problems caused by organic dyes, inorganic ions and other pollutants are becoming more and more serious, and the removal of pollutants from wastewater is still a challenge. A polyoxometalate-based metal organic framework [Pr₄(bpdc)₄(H₂O)₁₀]·SiMo₁₂O₄₀·3H₂O (1) (H₂bpdc = 2,2′-bipyridine-6,6′-dicarboxylic acid) was synthesized for multi-functional treatment of pollutants in water. Structural analysis revealed that Keggin-type polyanions are sandwiched between adjacent lanthanide-organic layers. Electrochemical and dye removal experiments showed that compound 1 can not only reduce NO₂⁻ and BrO₃⁻ pollutants in water by electrocatalytic oxidation, but also photocatalytically degrade and adsorb cationic organic dye pollutants in water, and even adsorb cationic organic dyes from mixed dyes solution. It has been proved that compound 1 is a multifunctional water treatment agent.

Bis-cyclometalated Ir(III) complexes Ir(ppy-Carbazole)₂(acac) and Ir(ppy-NPh₃)₂(acac) (acac = acetylacetonate) based on the 2-phenylpyridine (ppy) with carbazole or triphenylamine moieties were prepared, characterized and tested as phosphorescent materials. The photophysical properties of the two complexes were investigated by comparing them with the unsubstituted parent Ir(III) complex Ir(ppy)₂(acac). Complexes Ir(ppy-Carbazole)₂(acac) and Ir(ppy-NPh₃)₂(acac) with carbazole/triphenylamine-appended C^N cyclometalating ligands exhibit larger molar extinction coefficients and longer luminescence lifetimes compared to the unsubstituted parent Ir(ppy)₂(acac). Based on a rational design strategy by combining a ppy unit and electron-donating carbazole or triphenylamine segment, we investigated the merits of the carbazole or triphenylamine group substituted cyclometalated Ir(III) complexes for oxygen sensing. These probes demonstrate optimal luminescence dynamics for oxygen monitoring in the range of 0–100% oxygen levels when immobilized in an ethyl cellulose matrix. Importantly, the complex Ir(ppy-NPh₃)₂(acac) exhibits a longer luminescence lifetime (τ = 3.60 μs) and a higher oxygen sensitivity (I₀/I₁₀₀ = 15.0, K_SV = 0.02582 Torr⁻¹) compared with the other complexes.

Nanocrystalline (CoMn)₅₀Ni₅₀ powders were prepared by the mechanical alloying process in a high-energy planetary ball mill under an argon atmosphere. Morphology, structure, microstructure, and magnetic properties were investigated using scanning electron microscopy, X-ray diffraction, and magnetometry. The (CoMn)₅₀Ni₅₀ powders exhibit a highly disordered solid solution with a lattice parameter of a = 0.3542(4) nm, and undergo a ferromagnetic to paramagnetic transition at a Curie temperature of about 700 K. Different magnetic parameters were extracted from the approach to magnetic saturation. The electronic structure of the ferromagnetic powders was performed by the self-consistent ab initio calculations based on the Korringa–Kohn–Rostocker (KKR) method combined with the Coherent Potential Approximation (CPA). The total DOS is mainly due to the 3d-like states of the constituent elements Co, Mn, and Ni. The powders were tested in the discoloration reaction of Methylene Blue under different operation conditions via a heterogeneous Fenton-like process.

To remove the metronidazole, the iron oxides loaded on granular activated carbon (FeO_x-GAC) were prepared by the impregnation–calcination approach. The physicochemical properties of the catalysts were characterized by electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The results show that FeO_x-GAC has a porous structure, in which the iron oxides with a variety of valence states are smoothly attached on the activated carbon. The catalytic activity of FeO_x-GAC was evaluated for metronidazole removal, exhibiting great catalytic efficiency of the catalyst. Besides, the catalytic ozonation of metronidazole was optimized by varying the dose of ozone and catalyst, as well as the pH of the solution.

The synthesis and characterization of bromo- and iodo complexes of Pd(II) containing tridentate anionic Schiff bases, derived from the ring-opening of 2-R-2-(2-pyridyl)benzothiazoline precursors (R = H, 1; R = Me, 2; R = C₆H₅, 3; R = C₅H₄N, 4) is described. The [Pd(Lⁿ)X] complexes [for X = Br: n = 1 (1a), n = 2 (2a), n = 3 (3a), and n = 4, (4a); for X = I: n = 1 (1b), n = 2 (2b), n = 3 (3b), and n = 4 (4b)] were characterized in solution and in solid state by NMR and IR spectroscopy and by elemental analyses. In all complexes, the corresponding anionic Schiff ligand {Lⁿ}⁻ displayed a κ²NκS-tridentate coordination mode. X-ray diffraction studies of [Pd(L³)Br] (3a), [Pd(L³)I] (3b), [Pd(L⁴)Br] (4a), and [Pd(L⁴)I] (4b) complexes showed the formation of two five-membered chelate rings, with a distorted square planar geometry around the Pd(II) cation. Crystal structures of 3a, 3b, 4a, and 4b are stabilized by non-classical C–H···π, C–H···S, and C–H···X hydrogen bonding. The Hirshfeld surface analysis showed that the H···H contacts are predominant, and the C–H···S or C–H···π interactions were the major contributions in the stacking of the molecular complexes.