By taking advantage of a sequence of oxidative addition/reductive elimination reactions, Pt(II) cyclometalated derivatives are able to promote a rare C(spsup.2)-C(spsup.3) bond coupling, resulting in ...the production of novel methyl-substituted pyridines and bipyridines. Starting from 6-phenyl-2,2′-bipyridine, the step-by-step full sequence of reactions has been followed, leading to the unprecedented 3-methyl-6-phenyl-2,2′-bipyridine, which was isolated and fully characterized. The synthesis involves the following steps: (1) rollover cyclometalation to give the starting complex Pt(N^C)(DMSO)Me; (2) the synthesis of a more electron-rich complex Pt(N^C)(PPhsub.3)Me by the substitution of DMSO with triphenylphosphine; (3) oxidative addition with methyl iodide to give the Pt(IV) complex Pt(N^C)(PPhsub.3)(Me)sub.2(I); (4) iodide abstraction with silver tetrafluoborate to give an unstable pentacoordinate intermediate, which rapidly evolves through a carbon–carbon reductive coupling, forming a new C(spsup.3)-C(spsup.2) bond; (5) finally, the extrusion and characterization of the newly formed 3-methyl-6-phenyl-2,2′-bipyridine. The reaction has been therefore extended to a well-known classical cyclometalating ligand, 2-phenylpyridine, demonstrating that the method is not restricted to rollover derivatives. Following the same step-by-step procedure, 2-phenylpyridine was converted to 2-o-tolyl-pyridine, displaying the potential application of the method to the larger family of classical cyclometalated complexes. The application of this protocol may be useful to convert an array of heterocyclic compounds to their methyl- or alkyl-substituted analogs.
The nucleophilic addition of 3-(4-cyanopyridin-2-yl)-1,1-dimethylurea (1) to cis-Pt(CNXyl)sub.2Clsub.2 (2) gave a new cyclometallated compound 3. It was characterized by NMR spectroscopy (sup.1H, ...sup.13C, sup.195Pt) and high-resolution mass spectrometry, as well as crystallized to obtain two crystalline forms (3 and 3·2MeCN), whose structures were determined by X-ray diffraction. In the crystalline structure of 3, two conformers (3A and 3B) were identified, while the structure 3·2MeCN had only one conformer 3A. The conformers differed by orientation of the N,N-dimethylcarbamoyl moiety relative to the metallacycle plane. In both crystals 3 and 3·2MeCN, the molecules of the Pt(II) complex are associated into supramolecular dimers, either {3A}sub.2 or {3B}sub.2, via stacking interactions between the planes of two metal centers, which are additionally supported by hydrogen bonding. The theoretical consideration, utilizing a number of computational approaches, demonstrates that the C···dzsup.2(Pt) interaction makes a significant contribution in the total stacking forces in the geometrically optimized dimer 3Asub.2 and reveals the dsub.z sup.2(Pt)→π*(PyCN) charge transfer (CT). The presence of such CT process allowed for marking the C···Pt contact as a new example of a rare studied phenomenon, namely, tetrel bonding, in which the metal site acts as a Lewis base (an acceptor of noncovalent interaction).
Metal hydrides of AB5 compositions have been investigated over the years as they offer extraordinary volumetric hydrogen densities with high cycling stability and purity of released hydrogen. ...Moreover, by doping with different elements, the sorption properties of alloys can be significantly changed according to their foreseen applications. In this contribution, we report the synthesis routes and hydrogenation characteristics of Lasub.1−xYsub.xNisub.4.5Cusub.0.5. The synthesized alloys exhibit excellent structural purity with all reflections indexed by the hexagonal P6/mmm structure. It was found that the Y content can easily tune (raise) the equilibrium pressures of the pressure–composition isotherms, while overall gravimetric density remains at a level exceeding 1.5 wt.% up to x = 0.3 then strongly decreases. The pressure range for desorption can be tuned from 1.5 to 5 bars at room temperature. Some alloys (x = 0; 0.2) exhibit very good stability during 1000 cycles of hydrogen loading and unloading. Furthermore, activation of the alloys is prompt, making them good candidates for stationary hydrogen storage, non-mechanical hydrogen compressors, or soft actuators.
Jellyfish as food represent a millennial tradition in Asia. Recently, jellyfish have also been proposed as a valuable source of protein in Western countries. To identify health risks associated with ...the potential human consumption of jellyfish as food, trace element accumulation was assessed in the gonads and umbrella tissues of the Mediterranean Rhizostoma pulmo (Macri, 1778), sampled over a period of 16 months along the shallow coastal waters a short distance from the city of Taranto, an area affected by metallurgic and oil refinery sources of pollution. Higher tissue concentrations of trace elements were usually detected in gonads than in umbrella tissue. In particular, significant differences in the toxic metalloid As, and in the metals Mn, Mo, and Zn, were observed among different tissues. The concentrations of vanadium were slightly higher in umbrella tissues than in gonads. No positive correlation was observed between element concentration and jellyfish size, suggesting the lack of bioaccumulation processes. Moreover, toxic element concentrations in R. pulmo were found below the threshold levels for human consumption allowed by Australian, USA, and EU Food Regulations. These results corroborate the hypothesis that R. pulmo is a safe, potentially novel food source, even when jellyfish are harvested from coastal areas affected by anthropogenic impacts.
Most diseases that affect human beings across the world are now treated with drugs of organic origin. However, some of these are associated with side effects, toxicity, and resistance phenomena. For ...the treatment of many illnesses, the development of new molecules with pharmacological potential is now an urgent matter. The biological activities of metal complexes have been reported to have antitumor, antimicrobial, anti-inflammatory, anti-infective and antiparasitic effects, amongst others. Metal complexes are effective because they possess unique properties. For example, the complex entity possesses the effective biological activity, then the formation of coordination bonds between the metal ions and ligands is controlled, metal ions provide it with extraordinary mechanisms of action because of characteristics such as d-orbitals, oxidation states, and specific orientations; metal complexes also exhibit good stability and good physicochemical properties such as water solubility. Platinum is a transition metal widely used in the design of drugs with antineoplastic activities; however, platinum is associated with side effects which have made it necessary to search for, and design, novel complexes based on other metals. Copper is a biometal which is found in living systems; it is now used in the design of metal complexes with biological activities that have demonstrated antitumoral, antimicrobial and anti-inflammatory effects, amongst others. In this review, we consider the open horizons of Cu(II)- and Pt(II)-based complexes, new trends in their design, their synthesis, their biological activities and their targets of action.
SmCosub.5 constitutes one of the strongest classes of permanent magnets, which exhibit magnetocrystalline anisotropy with uniaxial character and enormous energy and possess high Curie temperature. ...However, the performance of SmCosub.5 permanent magnets is hindered by a limited energy product and relatively high supply risk. Sm is a moderately expensive element within the lanthanide group, while Co is a more expensive material than Fe, making SmCosub.5-based permanent magnets among the most expensive materials in the group. Subsequently, the need for new materials with less content in critical and thus expensive resources is obvious. A promising path of producing new compounds that meet these requirements is the chemical modification of established materials used in PM towards the reduction of expensive resources, for example, reducing Co content with transition metals (like Fe, Ni) or using as substitutes raw rare earth materials with greater abundance than global demand, like Ce and La. Important instruments to achieve these goals are theoretical calculations, such as ab initio methods and especially DFT-based calculations, in predicting possible stable RE-TM intermetallic compounds and their magnetic properties. This review aims to present the progress of recent years in the production of improved SmCosub.5-type magnets.
This study introduces a novel nanocomposite coating composed of PANI/CeOsub.2 nanocomposite films, aimed at addressing corrosion protection needs. Analysis through FTIR spectra and XRD patterns ...confirms the successful formation of the nanocomposite films. Notably, the PANI/CeOsub.2 nanocomposite films exhibit a hydrophilic nature. The bandgap energy of the PANI composite film is measured to be 3.74 eV, while the introduction of CeOsub.2 NPs into the PANI matrix reduces the bandgap energy to 3.67 eV. Furthermore, the electrical conductivity of the PANI composite film is observed to be 0.40 S·cmsup.−1, with the incorporation of CeOsub.2 NPs leading to an increase in electrical conductivity to 1.07 S·cmsup.−1. To evaluate its efficacy, electrochemical measurements were conducted to assess the corrosion protection performance. Results indicate a high protection efficiency of 92.25% for the PANI/CeOsub.2 nanocomposite film.
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