Chemistry - An Asian Journal最新文献

Selective hydrogenation of small hydrocarbons, exemplified by acetylene and 1,3-butadiene, under mild conditions is not only industrially critical but also serves as a benchmark for catalyst development. Designing effective supported metal catalysts for these reactions requires more than just high activity; it demands excellent selectivity to avoid over-hydrogenation and polymer formation, along with long-term stability under reaction conditions. While substantial progress has been made in developing selective hydrogenation catalysts, a systematic review that dissects the key factors affecting catalytic performance remains lacking. This review fills that gap by critically analyzing the roles of several fundamental parameters, including the geometric structure of supported metal species, support characteristics, the presence of secondary metal components, and the effects of controlled poisoning and coating of the active centers. By isolating and evaluating the impact of each factor, this review aims to provide clear insights that support the rational design of high-performance supported metal catalysts for selective hydrogenation. These insights are intended to guide future research toward more efficient, stable, and selective catalytic systems.

A visible-light-driven radical phosphinylation of alkynes under neutral conditions has been developed. This metal-free, redox-neutral protocol enables divergent synthesis, as alkyl alkynes afford 1,2-bisphosphonoethanes, whereas aryl, heteroaryl, or sterically hindered alkynes yield vinylphosphine oxides. The reaction exhibits excellent functional group tolerance and high regioselectivity, providing a green and practical route to valuable bisphosphonates and vinylphosphine oxides without requiring strong bases or transition-metal catalysts. Mechanistic studies indicate a radical pathway initiated by visible-light photolysis.

We have synthesized and characterized two covalently linked proton donor-acceptor supramolecular compounds: phthalocyanine-phenothiazine. These compounds exhibit an unexpected anti-Stokes shift. To elucidate the underlying mechanism, we investigated their UV–vis absorption spectra, steady-state fluorescence excitation and emission spectra, as well as time-resolved fluorescence decays in various solvents. The results reveal that intramolecular excited-state proton transfer gives rise to a higher-energy excited species, accounting for the observed anti-Stokes shift.

In this work, MoS₂@NiFe₂O₄ nanocomposites were engineered as electrode materials for both asymmetric (ASSC) and symmetric supercapacitors (SSC). The hybrid electrode combines the layered structure of MoS₂ and the redox-active spinel framework of NiFe₂O₄, offering better electrochemical performance. In the asymmetric configuration, the device demonstrated dual-potential-window functionality over –1.2 to 1.2 V, yielding strong redox activity and pseudocapacitive behavior with a specific capacitance of 102.36 F g⁻¹ at 10 mV s⁻¹. In addition, the ASSC attained an energy density of 12.08 Wh kg⁻¹ at a power density of 750 W kg⁻¹, exhibiting a Coulombic efficiency of 97.1% and a capacitance retention of 97.22% over 10,000 cycles. A high specific capacitance of 517.57 F g⁻¹ was achieved at a scan rate of 10 mV s⁻¹, and 483.42 F g⁻¹ was recorded using galvanostatic charge–discharge at 1 mA. The SSC achieved an energy density of 67.14 Wh kg⁻¹ at 750 W kg⁻¹ and maintained 99.25% of its capacitance after 10,000 cycles, exhibiting remarkably nearly 100% Coulombic efficiency. Mechanical flexibility tests confirmed the device's outstanding structural integrity under bending and twisting, indicating its applicability for flexible energy storage applications.

We report the synthesis of three novel 1,4-pyrene-embedded heptaphyrins in 5% yields via a [5 + 2] condensation of 1,4-pyrene pentapyrrane with dipyrromethene diols under mild acid-catalyzed conditions, followed by 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) oxidation. The key precursors, 1,4-pyrene pentapyrrane and 1,4-pyrene diol, were prepared from the literature-known 1,4-dithienylpyrene. While the previous pyreniporphyrinoids predominantly employed 1,3- or 1,3,6,8-linkages, this study represents the first-time use of exclusive 1,4-pyrene linkage to synthesize expanded macrocycles. These macrocycles were thoroughly studied using MALDI-MS, NMR, UV–visible absorption spectroscopy, electrochemical techniques, and theoretical calculations. The pyrene-embedded heptaphyrins are stable and display characteristic nonaromatic absorption features with absorption band at ~371 nm arising from pyrene moiety, while the sharp band at 478 nm and broad band in the 529–806 nm originating from the macrocyclic framework. Upon protonation, this broad band undergoes a significant bathochromic shift into the near-infrared (NIR) region, whereas the other two absorption bands remain unchanged or exhibit only a marginal red shift. Furthermore, electrochemical studies show that the macrocycles are electron-rich, exhibiting two irreversible oxidations and a reversible reduction. Ground-state optimization of the macrocycles reveals highly distorted, non-coplanar geometries with disrupted π-delocalization. Their nonaromatic character is further supported by NICS(0) calculations.

We present a comparative investigation of two main-group organoboron donor–acceptor (D–A) luminophores, carbazole-cyanostilbene-duryl-bridged dimesitylborane (CZ-CS-TAB) and anthracene-cyanostilbene-duryl-bridged dimesitylborane (AN-CS-TAB), to elucidate the influence of donor identity and molecular connectivity on their photophysical behavior in solution as well as solid-state. Both compounds were synthesized via stepwise Knoevenagel condensation followed by Suzuki–Miyaura coupling and characterized comprehensively by multi nuclear NMR, and HRMS spectroscopy. In solution state, CZ-CS-TAB exhibits hybridized local charge transfer (HLCT) excited state with moderate solvatochromism (440–475 nm), while AN-CS-wTAB displays only locally excited (LE) emission with minor solvatochromic response. Both systems demonstrate typical aggregation-induced emission (AIE) and solid-state emissive characteristics, accompanied by mechanochromic fluorescence (MFC) behavior. Mechanical grinding induces a reversible blue-to-cyan shift (460→495 nm→480 nm) in CZ-CS-TAB and a small red shift (530→540→535 nm) in AN-CS-TAB, correlating with a crystalline-to-amorphous transformation confirmed by PXRD. DFT and TD-DFT analyses support the donor-dependent HLCT and LE excited states, rationalizing the observed emission features. Both luminophores exhibit excellent thermal stability (T_d ≈ 350 °C). This study highlights how donor engineering coupled with borane acceptor frameworks enables systematic modulation of emissive, AIE, and mechanochromic properties, offering design strategies for multifunctional main-group organometallic luminophores.

The study introduces a metal-free, economical, and eco-friendly organo-catalyst featuring a hydrazonyl-quinone moiety, which can be conveniently synthesized in a one-step reaction from phenanthrenequinone and benzothiazole-hydrazine. The robustness of the catalyst is attributed to extensive π-delocalization, as ascertained through x-ray diffractometric and theoretical studies. Electrochemical analysis revealed two irreversible reductive responses at −0.68 and −1.30 V versus Ag/AgCl (cathodic peaks) in acetonitrile. Computational studies suggest that these reduction processes are primarily localized over the imino-quinone moiety. The catalyst has capable of trapping electrons in imino-quinone skeleton, facilitating redox reactions. This cost-effective organic catalyst efficiently mediates alcohol dehydrogenation and enables one-pot stepwise synthesis (OPSS) of diverse substituted triazines and pyrimidines in excellent yields under aerobic conditions, with favorable turnover numbers (TON) and turnover frequencies (TOF). The mechanism of catalysis has been proposed based on spectroscopic and control experiments and has been found to proceed via the formation of an imino-quinone radical, followed by hydrogen atom transfer (HAT) to form the aminoquinol intermediate. Due to its simple operation and workup without the need for metals, along with the cost-efficiency of the starting materials, this method offers a compelling alternative to existing synthetic approaches for substituted triazines and pyrimidines.

The development of efficient, stable bifunctional electrocatalysts for sustainable hydrogen production via water electrolysis remains challenging due to the high cost and instability of precious metal catalysts. This study addresses this by constructing a heterointerfacial CoFe₂O₄/CeO₂ composite anchored on carbon (CoFe₂O₄/CeO₂@C) through a facile hydrothermal-pyrolysis approach. The optimized catalyst demonstrates exceptional activity, achieving overpotentials of 243 mV for oxygen evolution reaction (OER) and 82 mV for hydrogen evolution reaction (HER) at 10 mA cm⁻² in 1 M KOH, significantly outperforming benchmark RuO₂ and Pt/C, alongside requiring only 1.57 V to drive overall water splitting at 10 mA cm⁻². Structural and electronic analyses confirm that the heterointerface between CoFe₂O₄ and CeO₂ facilitates charge redistribution, thus optimizing the electronic environment. Remarkably, the catalyst demonstrated only a 6.1% decay in current density after a 24-h stability test and exhibits high Faradaic efficiency. This work provides a scalable strategy for designing non-precious metal bifunctional catalysts for overall water splitting.