Chemistry - An Asian Journal最新文献

Polydiacetylenes (PDAs) have emerged as a promising class of stimuli-responsive materials due to their unique blue-to-red chromatic transition and associated fluorescence turn-on effect. These optical properties arise from the topochemical polymerization of diacetylene monomers into highly conjugated π-electron systems, enabling PDAs to function as dual-mode sensors. Their colorimetric and fluorimetric responses to external stimuli, including temperature, pH, mechanical stress, and chemical or biological interactions, have been widely exploited for sensing applications. PDA-based sensors have been developed for detecting volatile organic compounds (VOCs), metal ions, and pH changes, as well as for biological sensing of proteins, enzymes, and DNA. Additionally, PDAs have been utilized for environmental monitoring, including pollutant detection and mechanical strain assessment. A key strategy for enhancing PDA sensor performance involves adequate chemical modifications of the carboxyl-functionalized headgroup, which triggers a spectral change upon selective interactions with analytes. This review attempts to cover the strategies based on PDA headgroup modifications for tuning chromatic response, optical stability, and sensor efficiency, highlighting recent advancements and challenges. By exploring these modifications, this discussion aims to provide insights into the design of next-generation PDA-based sensors with improved performance and broader applicability.

The transition metal-catalyzed directed site-selective C─H bond functionalization utilizing allyl alcohols as coupling partner has been an intriguing area of research and has made considerable advances during the past decade. Multifunctional coupling characteristics of the allyl alcohol in the regioselective C(sp²)-H functionalization using transition metal-catalysis produces alkyl, alkenyl, allyl, and annulated products. These reactions provide an effective synthetic tool to afford diverse functionalized scaffolds that are of interest in synthetic and medicinal sciences. This review covers the developments of directed site-selective C(sp²)-H functionalization with unactivated allyl alcohols as the coupling partner using the transition metal-catalysis till December, 2024.

The amide functionalities are a crucial functional group in organic synthesis, playing a vital role in many processes that are essential for the efficient synthesis of important pharmaceutical and industrial compounds. Despite being one of the most commonly conducted reactions by researchers in both academia and industry, the synthesis of amides remains a staple in chemical research and development. Transamidation reactions enable the one-pot conversion of one type of amide into another. Additionally, this process is crucial in the complete synthesis of specific naturally occurring compounds. However, these methods have certain limitations such as using toxic and corrosive starting materials, usage of strong acid or base and metal mediated reaction, which can lead to excessive hydrolysis of the desired amide product. To overcome these challenges, more practical and efficient approaches have been developed. Metal-free transamidation reactions have emerged as a powerful and versatile synthetic methodology in organic chemistry, allowing for the direct conversion of amides into new amide products without relying on metal catalysts. In the review article, we have focused on various metal-free transamidation protocol of unactivated amides.

Zr-based MOF has been designed as a versatile adsorbent for the simultaneous removal of both As(III) and Hg(II) species with high adsorption efficiency. The synthesis procedure has been optimized to maximize the density of binding sites by introducing defects in the Zr clusters and incorporating amino functional groups into the linkers. The accessible binding sites result in high adsorption capacities of 626.71 mg g^-1 for As(III) and 4.24 mg g^-1 for Hg(II), which are among the highest reported values. The robustness of the adsorption performance was evaluated in various media with complex matrices, including river water and crude natural gas. Moreover, the preferential binding sites at the metal clusters and functionalized linkers were systematically investigated to elucidate their roles in the adsorption and offer new insights into the synergistic adsorption mechanisms for high removal efficiency.

Ortho-carboxyl-substitution increases the acidity of hypervalent diaryliodonium salts and makes them useful catalysts in the synthesis of bis(indolyl)methanes under mild conditions, with yields up to 98%. The halogen bond-assisted hydrogen bonding was demonstrated by crystal structure analysis. The interaction distance of 2.619 Å between I(III) and the carboxyl O atom indicates either a long covalent or a very short halogen bond; analysis of the electron density shows the latter description is appropriate.

The (anti)aromaticity of the two π-systems of cyclo[2n]carbons (n = 3-12) was analyzed based on its inherent properties: molecular structure, electron delocalization, and energetic (de)stabilization. Conclusions were made based on calculated bond length and bond angle alternation (BLA and BAA), bond order (BO), energy per atom, thermodynamic stability relative to acyclic analogues, aromatic fluctuation index (FLU), electron density of delocalized bonds (EDDB), vertical resonance energy (VRE), and extra cyclic resonance energy (ECRE). It was found that rings with n = 3, 5, and 7 are doubly stabilized by aromaticity. For n = 4 and 6, the out-of-plane π-system is nearly localized with RE similar to that of acyclic analogue, but the in-plane π-system is moderately stabilized by weak delocalization. The two π-systems behave similarly starting from cyclo[16]carbon. They are nearly localized and energetically almost unaffected by (anti)aromaticity.

Ceramics exhibit exceptional strength, hardness, and structural stability, rendering them indispensable as aerospace, national defense and biomedical applications. However, the presence of robust covalent or ionic bonds within the ceramic leads to its inherent poor fracture toughness. The incorporation of toughening phases into ceramics is widely recognized as an optimal toughening strategy for ceramic matrix composites (CMCs) based on chemical means, with the interplay between toughening phase and ceramic at the interface playing a crucial role in achieving superior mechanical properties. In this review, we briefly delineate the evolution of ceramic matrix composites, emphasizing that interface engineering constitutes an efficacious approach to augmenting the fracture toughness of these composites. Furthermore, we meticulously explore the structure-activity relationship between the composition and structure of the toughening phase and the mechanical attributes of CMCs. Additionally, we comprehensively summarize the impact of innovative biomimetic structures on the mechanical properties of these composites, unveiling the beneficial effects of interface regulation on energy dissipation. Ultimately, we systematically consolidate the mechanisms underpinning the influence of interface engineering on the mechanical properties of CMCs and propose solutions to existing interface challenges, paving the way for the development of next-generation CMCs that exhibit unparalleled strength and toughness.

The kinetic control of macrocyclic motions is a key aspect of mechanically interlocked molecules (MIMs). Although hydrogen bonding (H-bonding) offers a high reversibility and selectivity, the use of neutral H-bonding to control the macrocyclic mobility remains limited. In this study, the effects of H-bonding on the threading and dethreading kinetics of linked rotaxanes containing a permethylated α-cyclodextrin unit and an aniline moiety were investigated. UV-Vis spectroscopy revealed significantly reduced reaction rates in H-bond acceptor solvents, such as dimethyl sulfoxide (DMSO) and dimethyl formamide. NMR titrations and FT-IR spectroscopic analyses confirmed that H-bonding between the aniline moiety and these solvents acts as a "brake" during threading/dethreading. Moreover, Eyring plots indicated that enthalpic losses during H-bond cleavage contribute to the increased activation barriers for these processes. Additionally, the introduction of H-bond acceptors, such as DMSO and tributylphosphine oxide, effectively modulated these rates of threading and dethreading, highlighting the potential for controlling kinetic phenomena in MIM-based systems.

Here, two mixed-ligand mononuclear [Cu(L¹)py] (1), [Cu(L²)Him] (2) and one dinuclear copper(II) complex [Cu₂(L³)₂(DMSO)(MeOH)] (3) were isolated in solid state and characterized through single-crystal X-ray diffraction. Herein, we highlight the solution behavior of these complexes in solution medium through HRMS and ESR. Though the complexes maintain their integrity with respect to the ligand coordination, there is solvent or co-ligand exchange and generation of both [Cu(L)(py/Him)] or [Cu(L)(H₂O)] species. G-quadruplex (G4-DNA) structures in the human telomeric DNA (hTelo) and promoter regions of oncogenes (c-MYC) can behave as potential therapeutic targets for the cancer treatment. Hence, the interaction of these complexes with G4-DNA and also duplex DNA was investigated through spectroscopy and molecular docking studies. The results reveal that the copper complexes show higher affinity for G4-DNA over duplex DNA, with 3 demonstrating the strongest binding among them. The complexes have also been tested for DNA nuclease activity against pUC19 plasmid DNA. Finally, the complexes showed significant cytotoxicity towards cancerous cell lines, namely HeLa and MCF-7 in comparison to the noncancerous cell line NIH-3T3. Annexin V/PI double staining assay demonstrated the apoptotic mode of cell death caused by the complexes. Overall, the results of G4-DNA interaction and anticancer activity are consistent, suggesting G4-DNA is the target for their biological activity.

Solar-driven CO₂ reduction has gained significant attention as a sustainable approach for CO₂ utilization, enabling the selective production of fuels and chemicals. SnS₂, a non-precious metal sulfide semiconductor, has great potential in photocatalytic CO₂ reduction due to its unique physicochemical properties. However, low electrical conductivity and susceptibility to aggregation of pure SnS₂ lead to a high charge recombination rate and hinder the photocatalytic efficiency. In this study, we report that single/few-layered MXene induces ordered growth of SnS₂ through electrostatic interactions and in situ solvothermal heating. Interconnected SnS₂ nano-array with abundant sulfur vacancies was successfully prepared on MXene surface (Vs-SnS₂/MXene). This unique structure promotes the separation and migration of photogenerated charges and effectively inhibits electron-hole recombination. Compared with pure SnS₂, the average lifetime of photogenerated charges in Vs-SnS₂/MXene increased by 45.6 %. Meanwhile, its CO production rate reached 47.6 μmol⋅g^-1⋅h^-1, which was 2.6-fold higher than that of pure SnS₂ (18.3 μmol⋅g^-1⋅h^-1), and showed excellent photocatalytic CO₂ reduction performance in gas-solid-phase reaction mode. In addition, Vs-SnS₂/MXene also showed excellent stability. The results showcased the transformative potential of integration strategies for designing high-performance photocatalytic systems.