Search Results (7)

Non-noble metals catalyzed carbonylative reactions serve as straightforward and sustainable methods for the synthesis of functionalized carbonyl-containing compounds. Herein, a low-valent-tungsten-catalyzed reaction that enables the coupling of aryl iodides and alcohols or phenols was disclosed, employing the readily available W(CO)₆ as the effective catalyst and PPh₃ as ligand. Under the optimal reaction conditions, aryl iodides smoothly underwent carbonylative coupling reactions with alcohols or phenols, processing the feature of broad substrate scope and good functional groups tolerance. Furthermore, this conversion can be carried out on a gram scale, showcasing significant promise in the synthesis of pharmaceutical or biologically active compounds. Full article

This work proposes for the first time protecting–reflecting on both sides of plated mirrors and a solution to polycarbonate surface vulnerability to weathering and scratching using tungsten disulfide (WS₂) by mechanical polishing. The ability of the dynamic chemical plating (DCP) technique to deposit Ag films at the nanometer scale on a polycarbonate (PC) substrate and its characteristics to be metallized is also shown. These deposits hold significant promise for concentrated solar power (CSP) applications. Complementarily, the application of WS₂ as a reflective film for CSP by mechanical polishing on smooth polycarbonate surfaces is both novel and practical. This technique is innovative and scalable without needing reactants or electrical potential, making it highly applicable in real-world scenarios, including, potentially, on-site maintenance. The effects of surface morphology and adhesion, and the reflectivity parameters of the silver metallic surfaces were investigated. Wettability was investigated because it is important for polymeric surfaces in the activation and metal deposition immediately after redox reactions. The flame technique improved wettability by modifying the surface with carbonyl and carboxyl functional groups, with PC among the few industrial polymers that resisted such a part of the process. The change in the chemical composition, roughness, and wettability of the surfaces effectively improved the adhesion between the Ag film and the PC substrate. However, it did not significantly affect the adhesion between PC and WS₂ and showed its possible implementation as a first surface mirror. Overall, this work provides a scalable, innovative method for improving the durability and reflectivity of polycarbonate-based mirrors, with significant implications for CSP applications. Full article

Due to their high abundance, polymeric character, and chemical tunability, polysaccharides are perfect candidates for the stabilization of photoactive nanoscale objects, which are of great interest in modern science but can be unstable in aqueous media. In this work, we have demonstrated the relevance of oxidized dextran polysaccharide, obtained via a simple reaction with H₂O₂, towards the stabilization of photoactive octahedral molybdenum and tungsten iodide cluster complexes [M₆I₈}(DMSO)₆](NO₃)₄ in aqueous and culture media. The cluster-containing materials were obtained by co-precipitation of the starting reagents in DMSO solution. According to the data obtained, the amount and ratio of functional carbonyl and carboxylic groups as well as the molecular weight of oxidized dextran strongly affect the extent of stabilization, i.e., high loading of aldehyde groups and high molecular weight increase the stability, while acidic groups have some negative impact on the stability. The most stable material based on the tungsten cluster complex exhibited low dark and moderate photoinduced cytotoxicity, which together with high cellular uptake makes these polymers promising for the fields of bioimaging and PDT. Full article

The development of catalysts for the hydrodeoxygenation of bio-based feedstocks is an important step towards the production of fuels and chemicals from biomass. This paper describes in situ-generated bulk molybdenum and tungsten oxides in the hydrodeoxygenation of the lignin-derived compound guaiacol. The catalysts obtained were studied using powder X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, high-resolution transition electron microscopy, diffuse reflectance infrared Fourier transform spectroscopy, and Raman spectroscopy. The use of metal carbonyls as precursors was shown to promote the formation of amorphous molybdenum oxide and crystalline tungsten phosphide under hydrodeoxygenation conditions. The catalysts’ activity was investigated under various reaction conditions (temperature, H₂ pressure, solvent). MoO_x was more active in the partial and full hydrodeoxygenation of guaiacol at temperatures of 200–380 °C (5 MPa H₂, 6 h). However, cyclohexane, which is an undesirable product, was formed in significant amounts using MoO_x (5 MPa H₂, 6 h), while WO_x was more selective to aromatics. When using dodecane as a solvent (380 °C, 5 MPa H₂, 6 h), the benzene-toluene-xylenes fraction was obtained with a 96% yield over the WO_x catalyst. Full article

Recent developments in nanoprinting using focused electron beams have created a need to develop analysis methods for the products of electron-induced fragmentation of different metalorganic compounds. The original approach used here is termed focused-electron-beam-induced mass spectrometry (FEBiMS). FEBiMS enables the investigation of the fragmentation of electron-sensitive materials during irradiation within the typical primary electron beam energy range of a scanning electron microscope (0.5 to 30 keV) and high vacuum range. The method combines a typical scanning electron microscope with an ion-extractor-coupled mass spectrometer setup collecting the charged fragments generated by the focused electron beam when impinging on the substrate material. The FEBiMS of fragments obtained during 10 keV electron irradiation of grains of silver and copper carboxylates and shows that the carboxylate ligand dissociates into many smaller volatile fragments. Furthermore, in situ FEBiMS was performed on carbonyls of ruthenium (solid) and during electron-beam-induced deposition, using tungsten carbonyl (inserted via a gas injection system). Loss of carbonyl ligands was identified as the main channel of dissociation for electron irradiation of these carbonyl compounds. The presented results clearly indicate that FEBiMS analysis can be expanded to organic, inorganic, and metal organic materials used in resist lithography, ice (cryo-)lithography, and focused-electron-beam-induced deposition and becomes, thus, a valuable versatile analysis tool to study both fundamental and process parameters in these nanotechnology fields. Full article

The present work studies the tungsten carbide (WC/C) coatings deposited by using Plasma Enhanced Chemical Vapor Deposition (PECVD), with and without gases of Ar and N₂. Volatile hexacarbonyl of W was used as a precursor. Their mechanical and tribological properties were evaluated. The following values were obtained by using deposition process with N₂ of H_IT = 19.7 ± 4.1 GPa, E_IT = 221 ± 2.1 GPa, and coefficient of friction (COF) = 0.35 ± 0.09. Secondly, deposition without the aforementioned gas obtained values of H_IT = 20.9 ± 2 GPa, E_IT = 292 ± 20 GPa, and COF = 0.69 ± 0.05. WC/C coatings were annealed at temperatures of 200, 500, and 800 °C, respectively. Evaluated factors include the introduced properties, the observed morphology, and the structural composition of WC/C coatings. The process of degradation was carried out by using various velocities, depending on used gases and annealing temperatures. Full article

Tetradentate N₂S₂ ligands (such as bismercaptoethanediazacycloheptane in this study) have seen extensive use in combination with transition metals. Well-oriented N₂S₂ binding sites are ideal for d⁸ transition metals with square planar preferences, especially Ni^II, but also as a square pyramidal base for those metals with pentacoordinate preferences, such as [V≡O]²⁺, [Fe(NO)]²⁺, and [Co(NO)]²⁺. Further reactivity at the thiolate sulfurs generates diverse bi, tri, and tetra/heterometallic compounds. Few N₂S₂ ligands have been explored to investigate the possibility of binding to main group metals, especially group III (M^III) metals, and their utility as synthons for main group/transition metal bimetallic complexes. To open up this area of chemistry, we synthesized three new five-coordinate main group XMN₂S₂ complexes with methyl as the fifth binding ligand for M = Al, and chloride for M = Ga and In. The seven-membered diazacycle, dach, was engaged as a rigid stabilized connector between the terminal thiolate sulfurs. The pentacoordinate XMN₂S₂ complexes were characterized by ¹H-NMR, ¹³C-NMR, ⁺ESI-Mass spectra, and X-ray diffraction. Their stabilities and reactivities were probed by adding Ni^II sources and W(CO)₅(THF). The former replaces the main group metals in all cases in the N₂S₂ coordination environment, demonstrating the weak coordinate bonds of M^III–N/S. The reaction of XMN₂S₂ (XM = ClGa^III or ClIn^III) with the labile ligand W(0) complex W(CO)₅(THF) resulted in Ga/In–W bimetallic complexes with a thiolate S-bridge. The synthesis of XMN₂S₂ complexes provide examples of M^III–S coordination, especially Al–S, which is relatively rare. The bimetallic Ga/In–S–W complex formation indicates that the nucleophilic ability of sulfur is retained in M^III–S–R, resulting in the ability of main group M^III–N₂S₂ complexes to serve as metalloligands. Full article