Chemistry - An Asian Journal最新文献

Fluoride is ubiquitously present in the natural environment, and its excessive levels can pose serious threats to human health and industrial production. Among various fluoride pollution control methods, adsorption is recognized for its optimal cost-effectiveness and adaptability. The mechanism of fluoride adsorption and the adsorption capacities of various modified adsorbents have been comparatively analyzed :natural minerals, biomass materials, metal oxides, and several emerging types of adsorbents, among which metal-based adsorbents show the best performance. Four modification methods to enhance the performance of adsorbents have been summarized: acid activation, thermal activation, surface functional group modification, and composite materials. Ultimately, this paper identifies the current limitations of adsorption methods for fluoride removal, including insufficient adsorption capacity and a narrow pH range of applicability. These findings are expected to offer valuable insights for the advancement of adsorbent materials research.

Graphene has emerged as a promising support material for Cu-Zn catalysts in CO₂ hydrogenation to methanol due to its high surface area and potential for functionalization with heteroatoms like nitrogen and oxygen, with nitrogen believed to contribute to the reaction. In this study, we combined machine learning and data analysis with experimental work to investigate this effect. Machine learning (using a decision tree model) identified copper particle size, average pore diameter, reduction time, surface area, and metal loading content as the most impactful features for catalyst design. However, experimental results indicated that nitrogen doping on graphene support improved the space-time yield by up to four times compared to pristine graphene. This improvement is attributed to nitrogen's role in lowering the catalyst's reduction temperature, enhancing its quality under identical reduction conditions, though nitrogen itself does not directly affect methanol formation. Moreover, machine learning provided insights into the critical features and optimal conditions for catalyst design, demonstrating significant resource savings in the lab. This work exemplifies the integration of machine learning and experimentation to optimize catalyst synthesis and performance evaluation, providing valuable guidance for future catalyst design.

A library of three dinuclear complexes [Yb(hfac)₃(L)]₂⋅3(CH₂Cl₂) (1)⋅3(CH₂Cl₂), [Dy₂(hfac)₆(L)₃]⋅3(CHCl₃) (4)⋅3(CHCl₃), [Yb(tta)₃(L)]₂ (6), four dinuclear enantiomers [Ln(facam)₃(L)]₂⋅CH₂Cl₂ Ln=Dy ((-)7⋅CH₂Cl₂, (+)7⋅CH₂Cl₂) and Yb ((-)8⋅CH₂Cl₂, (+)8⋅CH₂Cl₂), two tetranuclear complexes [Ln₂(hfac)₆(L)]₂⋅(CH₂Cl₂)_n (Ln=Yb, n =1 (2)⋅CH₂Cl₂; Ln=Dy, n=0 (3)) and two pentanuclear complexes [Dy₅(hfac)₁₅(L)₃]⋅2(C₂H₄Cl₂) (5)⋅2(C₂H₄Cl₂) and [Nd₅(hfac)₁₅(L)₃]⋅2(CH₂Cl₂) (10)⋅2(CH₂Cl₂) (1,1,1,5,5,5-hexafluoroacetylacetonate (hfac^-), 2-tenoyltrifluoroacetylacetonate (tta^-), 3-(trifluoro-acetyl-(+/-)-camphorate (facam^-) and L=[4'-(4'''-pyridyl-N-oxide)-1,2':6'1''-bis-(pyrazolyl)pyridine] ligand) were isolated and characterized by single crystal X-ray diffraction. The final molecular architectures could be controlled by playing with the ionic radii of Yb(III), Dy(III) and Nd(III) ions and steric hindrance of the β-diketonate. Natural circular dichroism (NCD) highlighted no exciton CD couplet for chiral compounds. All the compounds involving Nd(III) in both O9 and N3O6, Dy(III) in O9 and Yb(III) in both O8 and N3O6 coordination sphere present field-induced SMM while Dy(III) in O8 environment displays SMM behavior in zero applied dc field. The relaxation of the magnetization occurs mainly through a Raman process with contribution of QTM in zero field and Direct process under applied field. The relaxation time of the magnetization increases with the enhancement of the steric hindrance of the ancillary β-diketonate ligands.

The reaction of hydrated cobalt(II) perchlorate salt with the rigid tripodal ligand, tris(3,5-dimethylpyrazolyl) phosphine oxide, (O)P(3,5-DMPz)₃, results in selective in situ hydrolysis of a P-N bond affording a neutral mononuclear Co(II) complex, [Co{(O)P(O)(3,5-DMP)₂}₂] (1^Co(II)). The X-ray crystal structure of 1^Co(II) shows that it is formed by the coordination of two monoanionic N₂O-tripodal (O)P(O)(3,5-DMPz)₂ ligands, leading to a Co^IIN₄O₂ coordination sphere with an elongated pseudo-trigonal antiprismatic geometry. The analysis of the dc magnetic data revealed that this compound shows a strong easy-axis magnetic anisotropy with D=-45.3 cm^-1 and |E|= 10.2 cm^-1. Ab initio theoretical studies further supported these values and therefore confirmed the axiality in the ground state, with the magnetic anisotropy axis lying along the P-Co(II)-P direction. Dynamic magnetic measurements confirmed slow relaxation of magnetization under an applied dc field of 0.15 T. The magnetic relaxation does not take place through an Orbach process but through a combination of direct and Raman processes and it is much faster than that observed for other trigonal antiprismatic Co(II) complexes. This is probably due to the comparatively smaller magnetic anisotropy of 1^Co(II), as a result of the larger distortion of its geometry generated by the non-symmetrical (O)P(O)(3,5-DMP)₂ ligand.

MXenes are the carbides and nitrides of transition metals which are two dimensional in structure. High surface area, remarkable hydrophilicity, enhanced electrical conductivity, and unique surface functional groups are some of the distinguished properties of MXenes. These features make them suitable for numerous applications across domains such as sensing, biomedicine, catalysis, and electromagnetic interference shielding followed by hydrogen generation and storage at the forefront. This article encompasses the discovery, structure, fabrication routes, and varied applications of MXenes with an emphasis on electrocatalysis in hydrogen evolution reactions and storage. The article depicts diverse compositions and surface modification routes for enhancing their properties. MXene-derived Z-scheme photocatalysts have also been explored for their applications in degrading organic pollutants and volatile organic compounds. The article brings out various concerns such as the self-restacking of MXenes due to van der Waals forces of attraction and their aggregation. Furthermore, it sheds light on the current status of MXenes and future development for sustainable energy technologies. Scaleup and high production costs are a few challenges that need to be addressed.

Azulene, a non-alternative aromatic hydrocarbon, has attracted significant attention due to its unique electronic properties, and potential applications in organic electronics and optoelectronics. This review highlights recent advances in the synthesis, reactivity, and functional properties of ring-fused azulene derivatives. The discussion encompasses classical synthetic routes, including the Ziegler-Hafner and Nozoe methods, as well as novel approaches such as transition metal-catalyzed cyclizations. Key advancements in the construction of benzo[a]azulenes, naphthoazulenes, and other polycyclic azulene frameworks are detailed, emphasizing their regioselective functionalization and enhanced stability. Moreover, the incorporation of azulene moieties into polycyclic aromatic hydrocarbons (PAHs) and heterocyclic systems is explored, highlighting their potential applications in organic light-emitting diodes (OLEDs), field-effect transistors (OFETs), and photovoltaic devices. Special attention is given to azulene-fused helicenes and nanographenes, which demonstrate promising chiroptical properties and extended π-conjugation. This review aims to provide a comprehensive overview of the synthetic strategies and emerging applications of azulene-based compounds, contributing to the development of advanced materials for future electronic and photonic technologies.

The term ligand isomerism stands for two or more isomeric coordination complexes having regioisomeric ligands coordinated around the metal center. Single-cavity discrete coordination cages (SCDCCs) and multi-cavity discrete coordination cages (MCDCCs) are exotic class of self-assembled complexes that should be suitable for exploration of ligand isomerism. This work describes rare varieties of double-cavity tetranuclear, triple-cavity pentanuclear and quadruple-cavity hexanuclear MCDCCs to exemplify ligand isomerism. Square planar Pd(II) and pyridine-based bis-, tris- and tetrakis-monodentate ligands are employed as the modular building blocks for constructing the cages. The frameworks of all the ten cages studied here (four reported and six new) contain trinuclear Pd₃L₆ type double-walled triangular core (or sub-framework) that is decorated with one, two and three units of Pd₂L₄ type entity or sub-framework resulting in tetra, penta and hexanuclear MCDCCs, respectively. Suitable incorporation of isomeric arms as part of the double-walled trinuclear core by sourcing from the basket of regioisomeric ligands would offer ligand isomerism in the MCDCCs. Our ligand design afforded four members for the tetra or pentanuclear and two for the hexanuclear architectures to demonstrate ligand isomerism in MCDCCs.

Photodynamic therapy has emerged as a potent strategy for treatment of cancer due to its non-invasiveness, minimal toxicity, high spatial selectivity, and potential for combination therapies. However, self-aggregation of photosensitizers, tumour hypoxia and low penetration depth of excitation photons remain prominent challenges towards its clinical application. Nanoscale metal-organic frameworks have emerged as one of the most promising materials due to their tunable composition which allows the adjustment of optical and chemical properties by changing the metal ions or organic linkers. Due to their high porosity, they serve as carriers for photosensitizers and demonstrate high tumour accumulation rates, target specificity, and penetration depth with enhanced permeability and retention effect. This review aims to explore recent developments in nanoscale metal-organic frameworks focusing on the design strategies to enhance their effectiveness in tumour microenvironment. Specifically, we have examined the approaches to address challenges posed by hypoxic tumour environment and tissue penetration depth of the various light sources. Furthermore, this review provides insights into the targeting strategies that improve the overall efficacy through stimulus-activated release and sub-cellular internalization of photosensitizers. Finally, we discussed the on-going challenges and some future directions for harnessing their full potential as therapeutic agents for effective outcome of photodynamic therapy.

The iridium(I) complexes [IrBr(cod)(κC-tBuImCH2PyCH2NRR')] (NRR' = NEt2, NHtBu) have been prepared by reaction of the corresponding functionalized imidazolium salt with the appropriate dinuclear compound [Ir(µ-OR)(cod)]2 (R = OMe, OEt). These compounds react with H2(g) (5 bar) to afford the pincer iridium(III) dihydrido complexes [IrBrH2(κ3C,N,N'-tBuImCH2PyCH2NRR')] in good yields. The complexes [IrBr(cod)(κC-tBuImCH2PyCH2NRR')] efficiently catalyzed the β-alkylation of a series of secondary alcohols and the N-alkylation of a range of aniline derivatives with primary alcohols, with good selectivities for the β-alkylated alcohol and monoalkylated secondary amine products, respectively, at low catalyst loading, typically 0.1 mol%, and sub-stoichiometric amount of base in toluene at 383 K. The pincer iridium(III) dihydrido complexes show a catalytic performance similar to that of the iridium(I) complexes in model alkylation reactions. Mechanistic studies on the activation of the catalyst precursors have shown that both type of complexes have the ability to activate benzyl alcohol through the dearomatization of the pyridine ring by selective deprotonation of the methylene linker between the pyridine and the imidazole-2-ylidene fragment. DFT calculations suggest that activation of both catalytic precursors could lead to th common pincer iridium(I) species [IrH(κ3C,N,N-tBuImCH2PyCH2NEt2)], which may be key to the borrowing hydrogen reaction mechanism.

(TMA)₂SnX₆ (TMA=tetramethylammonium; X=Cl, Br, I) compounds form vacancy-ordered halide double perovskites (VODPs) with TMA⁺ cation in the A-site, Sn⁴⁺ cation in the M-site and X^- anion in the halide site. This study reports the synthesis and the structural phase transition of (TMA)₂SnCl₆, (TMA)₂SnCl_0.7Br_5.3, (TMA)₂SnBr₆, and (TMA)₂SnI₆. All four halides crystallize in a cubic Fd $\bar{3}$ c symmetry at room temperature. At elevated temperatures, (TMA)₂SnCl₆ and (TMA)₂SnBr₆ show phase transition to a cubic Fm $\bar{3}$ m symmetry at 364 K and 369 K, respectively. While the phase transition of (TMA)₂SnCl₆ was reported earlier, that of (TMA)₂SnBr₆ is reported for the first time in this study. The synthesis and structures of (TMA)₂SnCl_0.7Br_5.3 and (TMA)₂SnI₆ are reported for the first time in this study, with calorimetry data showing a reversible transition at 363 K and 325 K, respectively. Further, the choice of halide ligand influences the bandgap and the colour of the compounds. The absorption edge lies at 3.60 eV for (TMA)₂SnCl₆, at 2.64 eV for (TMA)₂SnBr₆, and at 1.12 eV for (TMA)₂SnI₆. Such a wide tunability of bandgap across the ultraviolet to infrared regions in combination with the thermal phase change makes these perovskites interesting materials for thermal and solar energy storage applications.