Chemistry - An Asian Journal最新文献

Ethanol synthesis from CO₂ and H₂ is currently a hot topic of research in heterogeneous catalysis. However, the underlying mechanism has not yet been clearly elucidated. We propose that the synthesis involves several other reactions on the electrode surface, as evident by the formation of a mixed potential. In this study, we prepared solid catalysts, Ru/CoO_x and CuPd/C, as the nano-anode and nano-cathode components and carried out CO₂ hydrogenation in the presence of small amounts of water to facilitate ion conduction. Ethanol was produced along with CO, CH₄, and methanol at reaction temperatures below 473 K in the presence of both the catalysts. The activation energy for ethanol formation with Ru/CoO_x was found to be 25 ± 5 kJ mol⁻¹, which was much lower than those for the formations of CO (44 ± 4 kJ mol⁻¹), CH₄ (77 ± 7 kJ mol⁻¹), and methanol (81 ± 9 kJ mol⁻¹). In addition, the production of CO was promoted by the encapsulated water. These results also suggest a mixed-potential-driven mechanism for the synthesis of ethanol.

A series of two-dimensional Ln-nitronyl nitroxide radical coordination networks, namely, {[Ln(hfac)₃]₃(NITBzald)₂}_n (Ln = Gd 1 and Dy 2; NITBzald = 2-(4-benzaldehyde)-4,4,5,5-tetramethylimidazoline-l-oxyl-3oxide; hfac = hexafluoroacetylacetone) and {[Dy(tfa)₃]₃(NIT-4Py)₂}_n (3; tfa = trifluoroacetylacetonato; NIT-4Py = 2-(4-pyridyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide) were synthesized. These complexes are composed of five-spin magnetic building blocks ([Ln₃(NIT)₂]) formed by three Ln^III ions bridged by two NIT units which are extended into 2D structure via coordinated aldehyde or pyridine groups of the radicals. DC magnetic investigations indicate that ferromagnetic Dy–NO interactions dominate in complex 3 whereas antiferromagnetic couplings in complex 2 are predominant. AC magnetic susceptibility studies show that complex 2 just exhibits the onset of slow relaxation of the magnetization while complex 3 presents visible maxima of temperature/frequency-dependent χ″ signals under a zero dc field, evidencing SMM behavior. The observed distinct magnetic relaxation performances of two Dy derivatives could be ascribed to synergistic effect of the different ligand fields of Dy^III ions mainly arising from the distinct coligands (hfac vs. tfa) as well as magnetic exchanges.

Arylstannanes are versatile organometallic reagents, and efficient methods for synthesizing them remain in demand. We report two approaches that expand this chemistry. First, aryne insertion reactions into Sn–F, Sn–CN, Sn–alkynyl, and Sn–aryl bonds furnish fluoro-, cyano-, alkynyl-, and aryl-substituted arylstannanes with high regioselectivity and broad functional group tolerance. Mechanistic studies reveal a decisive role of fluoride in activating organostannanes and promoting Cu-assisted transmetalation. Second, we introduce a convenient protocol for generating stannylpotassium species from silylstannanes and t-BuOK. The stannylpotassium reagents, featuring fully ionic Sn–K bonds, exhibit superior nucleophilicity and smoothly convert diverse aryl halides, including sterically hindered and heteroaryl substrates, into arylstannanes at room temperature under transition metal-free conditions. Together, these aryne- and stannylpotassium-based strategies provide operationally simple and general routes to diverse arylstannanes of high synthetic utility.

We herein disclose a base-mediated annulation reaction between azaoxyallyl cation and arylbicyclo[1.1.0]butane carboxylates (BCBs) to access succinimidyl spirocyclobutenes. The base played a dual role in forming the electrophilic azaoxyallyl cation species and also generating an enolate species from BCB and HFIP also assisted the stabilization of the intermediates and cyclization. Control experiments reveal the explicit involvement of the azaoxyallyl cation.,

This study describes a palladium-catalyzed chemoselective direct arylation of polyfluoroarenes with chloro(hetero)aryl triflates, achieving site-selective functionalization at the C–Cl bond for the first time. The recently developed alkyl-pyrazole-based phosphine ligand (BirdPhos) proved essential for the success of this transformation, affording excellent yields with high chemoselectivity. Moreover, the catalytic system enables the efficient synthesis of a broad range of functionalized polyfluoroarene derivatives under mild, additive-free conditions. Notably, the reaction retains the triflate group in the products, providing a versatile functional handle for further derivatization and highlighting the broad applicability and synthetic utility of this method.

Iridium dioxide (IrO₂) is extensively used in the chlor-alkali industry as a catalyst for the chlorine evolution reaction (CER) and is a key component of dimensionally stable anodes (DSAs). However, its performance deteriorates in acidic media owing to its structural instability and mass transfer limitations at high current densities. To boost the CER activity, the electrical conductivity and corrosion resistance of IrO₂-based electrodes are improved by optimizing the electronic structure and distributing the surface-active sites. In this study, we synthesized a structure comprising porous carbon nanofibers (CNFs) to which IrO₂ nanoparticles and zinc single atoms were anchored (IrO₂@Zn–N₄–PCNFs). The optimized catalyst has a low overpotential (96 mV, 10 mA cm⁻²) and retains 99% of its initial current over 24 h, thereby outperforming the commercial DSA (119 mV, 95%). This enhanced performance is attributed to the abundant CER-active sites formed by the synergistic interaction between IrO₂ nanoparticles and Zn–N₄ sites. Additionally, the hierarchical porous structure and conductive CNFs provide a large surface area (384.58 m² g⁻¹) and allow efficient mass transport. This paper presents a promising strategy for designing durable high-performance CER catalysts and contributes to the development of next-generation anode materials for chlor-alkali electrolysis.

A TEMPO-mediated regioselective C(sp²)−H/C(sp²)−H cross-dehydrogenative coupling of quinoxaline-2(1H)-ones with imidazo[1,2-a]pyridines has been developed. The method afforded C3-(imidazo[1,2-a]pyridine-3-yl)quinoxaline-2(1H)-ones in good yields. Metal and photocatalyst-free conditions, broad substrate scope, scalability, and good functional group tolerance are the salient features of the developed methodology. Based on the control experiments, this reaction is believed to proceed through a radical pathway.

Doping is an effective way to improve the separation efficiency of photogenerated carriers, widen visible light adsorption, and tune the band structure of carbon nitride (g-C₃N₄, CN). Herein, Na, S co-doped CN (CNNS-x) photocatalysts were successfully prepared by a one-step thermal polymerization method using urea and sodium thiosulfate as the raw materials. The incorporation of Na and S not only improves the visible light response intensity and photogenerated carrier separation efficiency of CN but also enhances oxygen adsorption capacity and optimizes the energy band structure of the CN. The optimal CNNS-2.5 photocatalyst revealed a significantly enhanced photocatalytic performance and yielded 4.85 mM (24.25 mmol·g⁻¹·h⁻¹) H₂O₂ in 1 h under visible light irradiation. The above yield is 4.71 times that of CN. It also revealed good stability in four cycles. The active species capture test and ESR revealed that the photocatalytic mechanism for H₂O₂ production on CNNS-2.5 was a two-step, single-electron oxygen reduction reaction (ORR) pathway.