Transition Metal Chemistry最新文献

Ti clusters were successfully synthesized in isopropanol using laser ablation in liquid. According to the isotope pattern and the corresponding m/z ratio, the dominant peak is assigned to Ti₅(C₃H₈O)₁₃. Density functional theory (DFT) calculations, are applied to illustrate the interaction of isopropanol with Ti. Among the Ti_n(2−7) clusters, Ti₅ has the highest electrophilicity and chemical potential, justifying the reasonable stability of Ti₅ in forming the experimentally observed Ti₅-C₃H₈O complex. Natural bond orbital analysis shows that the various interactions emanating from σ→ σ* and LP→LP orbitals within the complex contribute to the high stability of the Ti cluster. Moreso, that the Ti—O bond is more of covalent than electrostatic since the Laplacian of electron density for the bond critical point is negative. Finally, the Ti clusters are found to catalyze the coupling of isopropanol to diisopropylether as evidenced from the calculated reaction pathways and high-resolution mass spectrometry analysis. The energy profiles in the reaction coordinates show that the triplet state pathway is the most thermodynamically preferred path. The energy barrier for the Ti₅ pathway are also lower compared to Ti₃ and Ti₇ pathways, showing that the reaction is favorable for Ti₅.

A dinuclear platinum(II) complex, [Pt₂(μ-L)₃(μ-HL)]·Cl·3H₂O·DMSO (1, HL = 4-Amino-5-pyridin-4-yl-2,4-dihydro-[1,2,4]triazole-3-thione, DMSO = dimethyl sulfoxide), has been synthesized and characterized. The X-ray crystal structural analysis shows that the complex crystallizes in the triclinic, space group (Poverline{1}). Each Pt(II) atom is four-coordinated with two N atoms and two S atoms from triazole ligands. The two platinum centers of the complex formed a paddle wheel motif with four N atoms and four S atoms from four chelating triazole ligands as bridges. The complex forms a 3D network structure by intermolecular hydrogen bonds and C-H…π interactions. The inhibition of complex 1 was evaluated against protein tyrosine phosphatase 1B (PTP1B) and T-cell protein tyrosine phosphatase (TCPTP). It has been found that the complex can both inhibit PTP1B and TCPTP with IC₅₀ values of 11 and 17 μM, respectively. By comparing with the other platinum complexes, we found that complex 1 exhibits more effective inhibition to PTP1B and TCPTP than the reported paddle wheel dinuclear platinum(II) complexes and weaker inhibition against the two protein tyrosine phosphatases (PTPs) than the mononuclear platinum(II) complex with Schiff base ligand. It is suggested that both the modification and change of the ligand and the spatial structure of the complex will influence their inhibitory ability against PTPs.

Bismuth tungstate (Bi₂WO₆) has received extensive research in a numerous area, including degradation, CO₂ reduction, organic transformations, etc. Due to their wide range of applications, the discovery and development of effective, environmentally safe, gentle, and affordable techniques for the synthesis of bismuth tungstate are critical in organic transformations. There have been reports on variety of multicomponent reactions employing the heterogeneous catalysts Bi₂O₃, BiVO₄, and as well Bi₂WO₆ nanoparticle. Among other materials, Bi₂WO₆ nanoparticles are perceived for their high reactivity at ambient temperature in an aquatic medium. The main objective of this study is to emphasize the mechanistic considerations, scope, benefits, and limits of recent catalytic improvements in the process of oxidation and other reactions. Consequently, the use of Bi₂WO₆ catalyst offers many advantages, including high yields, an ecologically friendly process, quick reaction times, and a straightforward work-up technique. It has been created to use a Bi₂WO₆ catalyst in an aqueous medium in a versatile, simple, one-pot, multi-component technique. This process offers easy-to-find, inexpensive reagents, quick reaction times, great yields, and high atom economy. In this review, we have elaborated how Bi₂WO₆ nanomaterials can be employed as effective and reusable catalysts for organic transformation.

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The synthesis of monoclinic (γ) tungsten oxide (WO₃) nanorods via facile Microwave-assisted hydrothermal route is reported in the present work. The structural characterization of the as-synthesized material by using X-ray diffraction and Fourier-transform infrared spectroscopy confirms the formation of crystalline WO₃ phase. The morphology and microstructural study along with elemental composition of the material as obtained by scanning electron microscopy and transmission electron microscopy, respectively, reveals the generation of one-dimensional WO₃ nanorods. The nanorods show substantial absorbance in the ultraviolet (UV) region with the bandgap and refractive index of 2.7 eV and 2.48, respectively. Here, the low value of bandgap without adding any catalyst or co-catalyst is attributed to the microwave treatment. The electrochemical properties of WO₃ are studied using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The nanorods show high current density at different potentials and diffusion-controlled behavior as exhibited by Warburg impedance. The anodic as well as cathodic peak current values are seen to be increased after the deposition of the thin film of FTO substrate indicating the better diffusion of ions in the electrolyte. The capacitive and diffusive contribution of the thin film is investigated at various scan rates using Dunn’s model which shows that the diffusive contribution of the thin film is 120 times more than the capacitive contribution confirming the diffusive behavior of the thin film. The exchange current density of the deposited film is calculated which is found to have higher value than that of bare FTO. I–V characteristics of WO₃ are compared with that of bare FTO which reveals the smaller resistance offered by WO₃ film. The equivalent circuit as obtained from Nyquist plot is used to estimate the resistance of electrolyte, film and charge transfer resistance along with the double-layer capacitance and Warburg impedance. Further, bode plot is analyzed to study the phase shift and thus the diffusive behavior of the material.

Novel manganese(II) complexes, 1–3, involving 1,10-phenanthroline and thiocarboxamide ligands, were prepared and characterized structurally using single-crystal X-ray diffraction that revealed monometallic and bimetallic nature of the octahedral complexes. The catalytic activities of 1–3 were investigated in the oxidation of selected primary and secondary alcohols. During the optimization of the oxidation reactions, 1, a bimetallic manganese(II) complex bearing phenanthroline and bridging anthranilate showed higher activity as catalyst precursor than monometallic 2 or 3 in the oxidation of primary alcohols. The catalytic reactions were carried out in the presence of various oxidants such as molecular oxygen, hydrogen peroxide and tert-butyl hydroperoxide (TBHP) and additives such as acetic acid and imidazole. In this study, the oxidant/additive combination of TBHP and imidazole was shown to be effective for the oxidation of substrates investigated and the degree of their impact on oxidation reaction is highly dependent on a balanced ratio between them. 1 and 2 were selected as the most effective catalyst precursor under optimized reaction conditions and revealed efficient for the oxidation of selected primary and secondary alcohols, respectively.

Azo-aldehyde compound L (1) was prepared by coupling 4-ethylbenzenediazonium chloride ions with salicylaldehyde, and the subsequent azo-Schiff bases HL¹ (2) and HL² (3) were obtained by the condensation of compound L (1) with o-chloroaniline and p-chloroaniline, respectively. New azo-Schiff base ligands and their nickel(II) and copper(II) complexes (4–7) were also prepared and characterized by various analytical and spectroscopic methods, such as, elemental analysis and FTIR, GC–MS and NMR spectra. The metal complexes revealed the central metal atom as being coordinated to two phenolate oxygen atoms and two imine nitrogen atoms of two azo-Schiff bases, bearing approximate square-planar geometries. Further, spectral anaylyses data and metal-ion complexations revealed azo-hydrazone tautomerism within the two azo-Schiff bases HL¹ (2) and HL² (3). Azo-hydrazone tautomerism was evident through the formation of novel neutral mononuclear dye-metal complexes [M(L¹)₂] and [M(L²)₂], with M=Cu(II) or Ni(II) and all the ligands being of the azo form. Characteristic evaluations of the dyes and their metal complexes were conducted using X-ray diffraction (XRD) and scanning electron microscopy/energy dispersive spectroscopy (SEM/EDX). XRD data revealed that the synthesized compounds were of crystalline structure. SEM studies showed that the surface morphologies of all the samples had different shapes and particle sizes. TGA studies were conducted for the thermal properties of the compounds synthesized. The ligands and the corresponding metal complexes displayed effective emissions upon UV irradiation. Ligands (1–3) showed 32, 38 and 35% quantum yields and 3.02, 3.57 and 3.30 ns excited-state lifetimes, respectively.

In this work, two compounds, namely [Cd₂(HL)(4,4′-bpy)(H₂O)]_n (1), [Cd₂(HL)(bpa)(H₂O)·2H₂O]_n (2) (2,3-bis(3,5-dicarboxylphenxoy)benzoic acid (H₅L), 4,4′-bipyridine (4,4^'-bpy) and 1,2-bi(4-pyridyl)ethane (bpa)), have been synthesized. Complex 1 showed three-dimensional metal–organic framework, which was assembled by carboxylic groups and one type of 4,4′-bpy ligand to layer structure, and further extended by the other type of 4,4′-bpy ligands, while complex 2 displayed 3D metal–organic framework with bpa hanging inside the hole. Fluorescence detection experiment showed that compound 1 can detect nitrofurazone, sulfachlopyridazine and sulfathiazole. In addition, compounds 1 and 2 can be served as luminescent probes for sensing Cu²⁺ ion.

Five new organotin(IV) complexes, Me₂SnL₂ (1), n–Bu₂SnL₂ (2), t–Bu₂SnL₂ (3), Ph₂SnL₂ (4), and Ph₃SnL (5), have been designed and synthesized by the reactions of the deprotonated 1-adamantanethiol ligand (L = C₁₀H₁₅S) with the corresponding R₂SnCl₂ (R = Me, n–Bu, t–Bu, Ph) and Ph₃SnCl. The complexes were characterized by elemental analysis, FT-IR, NMR spectroscopy, and X-ray crystallography. Meanwhile, optimized geometrical parameters, harmonic vibrational frequencies, and frontier molecular orbitals were calculated. The in vitro cytotoxicities of the complexes were evaluated with HeLa and HepG-2. Furthermore, the antifungal activity of the newly synthesized complexes has been evaluated, and the SEM and TEM images were prepared from Alternaria kikuchiana Tanaka to analyze the macroscopic action of the drug on the fungus. As a result, complex 5 has good antifungal activity and cytotoxicity.

Electrocatalytic water splitting to produce hydrogen is a promising route to provide green hydrogen on a large scale. To explore non-noble metal electrocatalysts with high performance is still a challenge. Herein, a one-step electrodeposition way is developed to construct the heterostructural (NiO-La₂O₃)/(Ni-La)/NiO/Ni electrocatalysts on Ni foam. The dark Ni-La coating was prepared by co-electrodeposition from an aqueous solution containing LaCl₃ and NiCl₂ with a molar concentration ratio of 1:5. Among these heterostructural Ni-based electrocatalysts, an excellent HER activity is achieved: an overpotential of 22 mV at the current density of 10 mA cm⁻² in 1 M KOH solution. It is demonstrated that the introduction of La significantly reduces the overpotential for HER. The higher the La content in the Ni-La coating of these electrocatalysts, the better the electrocatalytic HER performance was exhibited. This work provides a facile and inexpensive route to prepare Ni-La coating on electrodes in an aqueous solution.

A novel single-component conductor derived from neutral radical gold bis(dithiolene) complexes is prepared based on the original reactivity of tBuN-substituted 1,3-thiazoline-2-thione heterocycle to give a tBuS-substituted thiazole ring. The corresponding 2-(tert-butylthio)-1,3-thiazole-4,5-dithiolate ligand (tBuS-tzdt) forms the d⁸ anionic complex [Au(tBuS-tzdt)₂]⁻, easily oxidized through electrocrystallization into the neutral radical [Au(tBuS-tzdt)₂]^·. The effect of increasingly bulky R groups (R = Et, EtOH, tBu), in the series of such radical complexes [Au(RS-tzdt)₂]^·, is investigated, with a focus on their solid state organization, either into face-to-face dimers or into non-dimerized, uniform stacks.