Chemistry - An Asian Journal最新文献

Facilitating cell migration to injury sites is critical for repair. This process is significantly influenced by mechanotransduction, where cells sense and dynamically respond to extracellular mechanical cues, especially viscoelasticity. However, within viscoelastic microenvironments, the relative dominance of stiffness versus stress relaxation in directing migration remains unresolved. This necessitates biomaterials enabling independent tuning of viscoelasticity. In this study, we engineered a transparent hydrogel platform by synergistically crosslinking oxidized hyaluronic acid (oxi-HA) and gelatin methacryloyl (GelMA) via covalent bonds and dynamic Schiff base linkages. Precise modulation of the bond ratios achieved decoupled control over stiffness and stress relaxation. In vitro studies assessing fibroblast and epithelial cell migration on hydrogels with varying stiffness (2.3-11.5 kPa) and relaxation times (2.3-17.2 s) revealed substrate stress relaxation as the dominant cue governing migration. Furthermore, the cornea-like optical transparency (>90%), through the optimized formular, was achieved, and the hydrogel's drug release capacity was evaluated.

We report catalytic performance of a stable 3D metal-organic framework (MOF), {Mn₂(1,4-bdc)₂(DMF)₂}_n (Mn-BDC) (1,4-bdcH₂, 1,4-benzenedicarboxylic acid; DMF, N,N-dimethylformamide) in water and solventless condition. The coordinated DMF molecules in the MOF can be removed by heating to yield a desolvated phase, Mn-BDC^Desolv with unsaturated Mn(II) sites (unsaturated metal sites [UMSs]) acting as Lewis acid sites, whereas the Lewis basicity arises from the carboxylate oxygens of 1,4-bdc. Mn-BDC^Desolv is explored as a bifunctional heterogeneous catalyst to synthesize several benzylidenemalononitrile (BMN) derivatives in water and α-aminonitriles in solventless condition. The catalyst demonstrates excellent conversion (>99%) and high turnover number (TON) up to 16,500 and turnover frequency (TOF) up to 550 min^-1. Remarkably, Mn-BDC^Desolv maintained >99% conversion over 24 cycles during the synthesis of BMN derivatives. The catalysts broad substrate scope, robust nature, superior TON, and TOF values compared to the benchmark MOFs and high recyclability highlights its potential for various Lewis acid-base-catalyzed organic transformations. It is important to mention that Mn-BDC can be prepared in gram scale in lab easily making the catalyst economical. Further, the catalytic process with Mn-BDC can be termed "green" as it allows the reactions to proceed either in water or in solventless condition.

BODIPY-malonitrile conjugates showed intriguingly solvent-dependent site-switching nucleophilic additions by cyanide, acting as two-channel fluorescent receptors for rapid, selective, and sensitive detection of cyanide anion as low as 0.28 µM. In aqueous solution, the probes were found to rapidly react with cyanide anion via a typical Michael addition to the malonitrile group at vinyl β-carbon, giving a rapid, selective, and sensitive "turn-on" detection of the cyanide anion. Unprecedentedly, in THF solution, the cyanide anion showed an unprecedented conjugated addition to the azafulvene ring of the BODIPY unit at vinyl α-carbon, followed by a tautomerization reaction, exhibiting significant (up to ∼116 nm) blue shifts in the absorption maxima.

As a key parameter in organismal growth and development, pH is essential for maintaining internal environmental homeostasis, ensuring normal metabolic processes, and coordinating the functions of various organ systems. In this study, we developed a series of aza-IR780-based heptamethine cyanine ketones that exhibit remarkable pH-responsive behavior, governed by keto-enol tautomerism occurring along the conjugated polyene backbone of the cyanine scaffold. Under neutral conditions, these cyanines predominantly adopt the keto form, displaying a fluorescence emission maximum at approximately 640 nm. In acidic environments, however, they shift to the enol form, resulting in a distinct fluorescence redshift to around 740 nm. This pronounced pH-dependent spectral response enables real-time visualization and monitoring of pH fluctuations within plant tissues. Our work thus offers a promising molecular tool for noninvasively imaging the microenvironment in plants.

Possible mechanisms of isothiourea-catalyzed acylation of N-aminoindole with benzoyl chloride for constructing N─N axial chirality have been systematically investigated using density functional theory (DFT). Two pathways initiated by the nucleophilic addition of NEt₃ and isothiourea catalyst to benzoyl chloride have been explored, respectively. The calculation results revealed that the energetically favorable pathway proceeds in three steps, including formation of an amide iminium cation by nucleophilic addition of NEt₃ to benzoyl chloride, S_N2 reaction to form an acylisothiouronium intermediate using isothiourea catalyst coupled with elimination of NEt₃, and C-N bond formation accompanied by regeneration of isothiourea catalyst. Among these steps, the C-N bond formation between the acylisothiouronium intermediate and the amide anion has been identified as the stereoselectivity-determining step to construct the N─N axially chiral compound. Distortion-interaction analyses revealed that interaction energy dominates the stereoselectivity-determining step. Furthermore, the key factors that determine the stereoselectivity have been confirmed by noncovalent interaction (NCI) and atoms-in-molecules (AIM) analyses. The nucleophilicities of NEt₃ and the isothiourea catalyst have been further analyzed using Parr functions and Fukui function vectors.

Salinity gradient energy is a promising marine renewable source that requires high-performance electrode materials for efficient harvesting. While polyaniline (PANI)-intercalated V₂O₅ enhances ion transport through an expanded interlayer spacing, its practical application is hampered by inherently low electrical conductivity and structural instability. In order to solve the structural stability problem, we co-intercalate Ce³⁺ and PANI into V₂O₅ layers Ce@PANI@V₂O₅ (CPVO), to stabilize the interlayer structure for improving the electrochemical conversion of salinity gradient energy. The results show that the Ce-N and Ce-O bonds formed by the co-intercalation of Ce³⁺ and PANI stabilized the interlayer structure, and brought a larger pore area, which improves the electrochemical performance of the electrode material. The CPVO has a specific capacitance of 238.0 F g^-1 at a current density of 0.2 A g^-1. After 1000 cycles, the capacity retention rate is 90.36%. The AC//(0.083 M Na₂SO₄, 0.5 M Na₂SO₄)//CPVO salinity gradient energy conversion device successfully converted an energy density of 9.10 J g^-1, paving the way for high-efficiency salinity gradient energy conversion systems.

Two tetranuclear Cu(II) complexes [Cu₄L₂(μ₃-OCH₃)₂](ClO₄)₂∙2H₂O (1) and [Cu₄L₂(H₂O)₂(μ₃-OH)₂](NO₃)₂∙H₂O (2) (H₂L = 2,6-diformyl-4-methylphenol bis(thiosemicarbazone)) have been synthesized. Two types of sulfur atom-bearing L^2- scaffolds were obtained through tautomerization of the thiosemicarbazone arms. Geometric arrangements of [Cu₂(μ₃-OMe)₂Cu₂] and [Cu₂(μ₃-OH)₂Cu₂] are found for tetranuclear complexes. Reactions of Cu(ClO₄)₂∙6H₂O and Cu(NO₃)₂∙3H₂O with H₂L were utilized with linkers HO^- and MeO^-. These synthesized complexes have been characterized by x-ray crystallography, and their magnetic properties have been examined. Complexes 1 and 2 showed fluorescence quenching behavior with respect to the free H₂L. Complexes 1 and 2 exhibit catalytic oxidation reactivity for the 2-aminophenol and 3,5-ditertbutyl catechol, effectively mimicking the enzymes catechol oxidase and phenoxazinone synthase, respectively. The turnover numbers k_cat for 3,5-DTBCH₂ and AP are 13.32 (1), 25.56 (2) and 23.04 (1), 13.35 (2). From the variable temperature magnetic susceptibility measurements, the obtained J values ranged between -200 and -500 cm^-1 and were found to be highly correlated, which indicates the strong antiferromagnetic interactions between the interlinked copper(II) centers. For complex 1, the values are g = 2.13, J = -470 cm^-1, ρ = 1.4% and for compound 2 these are g = 2.08, J = -480 cm^-1, ρ = 2.5%.

This special issue highlights advances in biomass-derived carbon materials, activated carbon, graphene, nanotubes, and soft/hard carbon, produced from diverse biomass sources for smart, sustainable applications. The graphical abstract illustrates their role in promoting circular economy, energy efficiency, environmental sustainability, and emerging technologies through innovative, eco-friendly carbon material design and utilization.

The sustainable development of efficient and stereocontrolled catalytic strategies for the synthesis of biologically relevant glycosides is of paramount importance in modern glycoscience. Herein, we report an operationally simple and scalable catalytic system employing an easily accessible, highly stable, and inexpensive pyridinium tetrafluoroborate salt as an effective organocatalyst for the stereoselective synthesis of β-O- and N-glycosides. The protocol utilizes readily available glycosyl trichloroacetimidates (TCAs) as donors and accommodates a broad range of aliphatic alcohols (including sugar and non-sugar derivatives) as well as challenging arylamines as acceptors, delivering the corresponding O- and N-glycosides in good to excellent yields with high to exclusive β-anomeric selectivity under mild reaction conditions. Mechanistic investigations suggest that the catalyst facilitates selective glycosylation through non-covalent interactions (NCIs) between catalyst and acceptor, which contribute to both donor activation and stereochemical control. The utility and robustness of the methodology are further demonstrated through gram-scale synthesis and the construction of trisaccharide.