Precision Chemistry最新文献

Heterogeneous catalytic N-alkylation has increasingly been recognized as a sustainable approach for the formation of C-N bonds, particularly in the synthesis of high-value nitrogen compounds. Based on the characteristic that calcined hydrotalcites exhibit basic sites of varying strengths depending on their Mg/Al molar ratios, this study employed Mg-Al layered double hydroxides (LDHs) as precursors to synthesize a series of layered double oxides (LDOs) with different Mg/Al ratios via high-temperature topotactic transformation. These LDOs were then used as solid base catalysts to investigate the mechanistic influence of basic site strength on the N-alkylation of 1,2-benzisothiazolin-3-one (BIT) for the selective synthesis of N-butyl-1,2-benzisothiazolin-3-one (BBIT). Notably, Mg₄Al₁O-600 showcased superior catalytic activity, achieving a BIT conversion rate of 61.66% and a BBIT yield of 42.81% within 20 h. A structure-property correlation analysis suggests that the abundant medium-strength basic sites function as active centers for selective N-alkylation, thereby significantly improving selectivity toward BBIT. The predominant catalytic mechanism is identified as an S_N2 nucleophilic substitution. Additionally, kinetic analysis indicates that the reaction is largely influenced by the coupled mass transfer and reaction behavior of BIT.

Stimulated emission depletion (STED) microscopy requires fluorescent probes to exhibit high brightness, good photostability, a sensitive optical depletion response, and narrow spectral features. There are great interests in using polymer dots (Pdots) for STED imaging due to their exceptional brightness and photobleaching resistance. However, the conventional Pdots either suffer from broad spectra or an unsatisfactory STED response. Herein, we developed a general method for obtaining Pdots with desirable optical properties for STED microscopy. Specifically, boron-dipyrromethene (BODIPY) chromophores were grafted on to a polystyrene backbone to obtain polymers with narrow spectral profiles. The grafting ratio was precisely controlled to minimize aggregation-induced quenching. Conjugating BODIPYs to side chains reduced interactions between the chromophores, resulting in a long excited state lifetime, which is critical for obtaining complete fluorescence depletion. Using this strategy, we synthesized three-color Pdots with narrow spectra features. Compared to directly encapsulating BODIPYs into nanoparticles, our strategy achieved 2-10 times higher single-particle brightness. We used Pdots for single-particle, cellular, and tissular STED imaging. The Pdots showed high spatial resolutions and could clearly resolve subdiffraction-limit structures in cells and tissue sections, indicating great application potential in in vitro diagnostics and biomedical imaging applications.

Construction of high-order 2:2 complexes has not been reported for carbon nanohoop systems owing to the synthetic challenges of the host and the complexity of the binding process. In this work, a cycloparaphenylene double-decker host (1) was synthesized and its structure was determined by single-crystal analysis, revealing a trans-geometry and a self-assembled dimerization. Crystallographic studies and NMR/UV-vis titrations demonstrated the stepwise formation of a 1:2 complex between 1 and C₆₀. For the complexation of 1 and C₁₂₀, a highly cooperative 2:2 complex was formed, exhibiting the formation constant K _F = (1.2 ± 0.2) × 10¹⁷ M^-3; this complex disassembles into a 1:2 complex with the breaking constant K _B = (1.6 ± 0.3) × 10⁴ M^-1 upon addition of excess C₁₂₀. This distinctive binding-unbinding process is supported by single-crystal analysis, NMR titration, and diffusion-ordered NMR spectroscopy. The study highlights the potential of concave-convex π-π interactions in forming high-order complexes, which could facilitate the development of more sophisticated supramolecular architectures.

Biobased reactive diluents are an alternative to fossil-based compounds, such as styrene, used in industrial-scale manufacturing. We proposed a more scalable, sustainable, and applicable synthesis of methacrylated biobased monomers involving a cheap and affordable catalyst, potassium acetate, as a substitute for the currently used 4-dimethylaminopyridine (DMAP). Also, the isolation of the formed byproduct during the synthesis, methacrylic acid, is involved in the introduced approach to reduce disposal waste and increase the production process's scalability. The synthesized biobased monomers based on vanillin, cinnamyl alcohol, vanillyl alcohol, and isosorbide were characterized via NMR, ESI-MS, and FTIR structural-verifying cross-analysis. We investigated all produced reactive diluents' rheological profiles, reactivity, and thermomechanical properties. Glass-containing composites were fabricated using the synthesized reactive diluents instead of the commercially applied styrene. The best-performing material, vanillin methacrylate (V-Mono MMA), reached a viscosity (η) of 621 mPa·s at 30 °C, a storage modulus (E') of 2450 MPa at 45 °C, a glass transition temperature (T _g) of 130.4 °C, a heat-resistant index (T _S) of 149.7 °C, a flexural modulus (E _t) of 41.4 ± 1.2 GPa, a flexural strength (σ_fM) of 1201.8 ± 54.3 MPa, and an interlaminar shear strength (σ_sbs) of 52.12 ± 0.6 MPa.

Visible-light-mediated functionalization of bicyclo[1.1.0]-butanes (BCBs) has been proven to be an efficient way to obtain diverse cyclobutane derivatives. However, achieving diastereoselective control in this field remains challenging. Herein, we reported a mild photoredox-catalyzed aminopyridylation of BCBs with N-aminopyridinium ylides, delivering the cyclobutylamine derivatives with excellent regio- and diastereoselectivities. This protocol demonstrated excellent compatibility with a wide range of BCBs and N-aminopyridinium ylides, and the value of this approach was highlighted by its application in the preparation of high-value, structurally complex cyclobutane derivatives.

Tumor-derived extracellular vesicles (EVs) have emerged as promising targets for liquid biopsy, enabling noninvasive mRNA profiling to support cancer detection, staging, and treatment monitoring. This Review highlights the development and clinical translation of EV Digital Scoring Assays, an innovative class of two-step liquid biopsy platforms integrating click chemistry-mediated tumor EV enrichment (via EV Click Beads or EV Click Chips) with reverse transcription digital PCR (RT-dPCR) for absolute quantification of tumor mRNA. These assays have demonstrated clinical utility across multiple solid tumors: identifying oncogenic alterations in pancreatic ductal adenocarcinoma and Ewing sarcoma, detecting early stage hepatocellular carcinoma in at-risk cirrhotic patients, differentiating localized from metastatic prostate cancer, and monitoring treatment response in hepatocellular carcinoma. We also examine emerging technologies and parallel efforts from other groups, including microfluidic isolation platforms, PCR-free digital detection, and machine learning-based analytics. Together, these studies showcase how "enrich-then-count" strategies can overcome challenges in tumor EV specificity and transcript quantification, offering scalable solutions for precision oncology. The EV Digital Scoring Assay provides a versatile and modular platform, potentially enabling broad adoption across diverse tumor types and clinical contexts for real-time noninvasive cancer management.

A photoresponsive hexa-arylazopyrazole-substituted tris-(β-diketonato) Co-(III) complex was synthesized, and the Λ- and Δ-enantiomers were isolated. The complex shows reversible E/Z isomerization using UV (λ_max = 365 nm) and visible light (λ_max = 520 nm), respectively. Using the Co-(III) complex as a dopant in the commercially available liquid crystal N-(4-methoxybenzylidene)-4-butylaniline (MBBA), the chiral nematic phase can be induced. Upon photoisomerization, the helical pitch of the doped liquid crystal can be reversibly modulated, leading to very high changes in terms of helical twisting power (HTP or β _M ). Corresponding to this change, the HTP value of the doped liquid crystals varied between 615 and 346 μm^-1 or between -563 and -352 μm^-1 at 30 °C, where the positive and negative signs correspond to the P and M helix, respectively. Thus, the Co-(III) complex effects both high HTP values of the liquid crystal and large changes upon photoisomerization, enabling induction of the chiral nematic phase at very low dopant concentrations, which can be useful for the development of optical applications.

Chemical oxidation of a perylene and coronene mixture with GaCl₃ results in the formation of a unique mixed polycyclic aromatic hydrocarbon (PAH) product of the composition, [(C₂₀H₁₂)₂(C₂₄H₁₂)]²⁺(GaCl₄ ^-)₂·(C₆H₆)₂, as revealed by single crystal X-ray diffraction. The crystal structure exhibits π-stacked columns of repeating perylene-perylene-coronene units, with π-stacks separated by GaCl₄ ^- anions and benzene molecules. Interplanar contacts in the asymmetric PAH trimer average 3.352(2) Å, with an atom-over-atom π-surface overlap between neighboring perylene and coronene. In the solid-state, multiple H···Cl contacts between the perylene moieties and GaCl₄ ^- anions are present, with additional C-H···π contacts found between coronene and benzene molecules. The EPR spectrum of the crystals shows a strong singlet with a g-factor of 2.0041, indicative of an organic radical persistent in a very broad temperature range. The UV-vis absorption spectra point to the asymmetric charge distribution in the mixed PAH trimer, in accord with core deformation revealed crystallographically. The original crystal structure is used as a model for in-depth theoretical description of bonding and charge assignment within a heteromolecular PAH trimer. Computational studies reveal that the surrounding GaCl₄ ^- and benzene units play a crucial role in stabilizing the structure and modulating the electronic properties of the perylene-perylene-coronene stacks. Computational results also fully support the interpretation of the uneven charge distribution based on solid-state characteristics and spectroscopic data.

The production of hydrogen through photocatalytic water splitting has attracted considerable interest as a means of hydrogen energy. The electron-hole recombination in photocatalysts can affect the efficiency of photocatalytic hydrogen production. Therefore, the rational regulation of photogenerated electron transport has become an effective approach to enhancing hydrogen production efficiency and addressing energy challenges. Based on density functional theory (DFT) and nonadiabatic molecular dynamics (NAMD) simulations, the MoSi₂N₄/ZrS₂ (HfS₂) heterojunctions were built. The electronic properties, optical properties, interface properties, carrier transport after illumination, and photocatalytic performance of the heterojunction are investigated. The results indicate that after constructing the heterojunction, light absorption and carrier mobility significantly increased. The electron-hole pairs were effectively separated, and hydrogen production efficiency has shown a marked increase. Furthermore, the corresponding mechanistic explanation was provided. This study provides a theoretical foundation for the further development of efficient two-dimensional heterojunction photocatalysts.

Upon interaction with H₂, metal oxides can be reduced. Such a reduction may consequently alter their interactions as well as the evolution of hydrogen species on metal oxide surfaces. However, this has not been thoroughly and precisely studied on the atomic scale. Accordingly, systematic density functional theory (DFT) calculations were performed on a representative metal-oxide catalyst surface, namely β-Ga₂O₃(100). It was found that oxygen vacancy clusters can readily form upon reduction and that such vacancy clusters enable the infiltration of surface hydrogen species into the near-surface region. The calculated relative population of near-surface hydrogen species reaches approximately 5% under typical experimental conditions for hydrogenation and dehydrogenation reactions on Ga₂O₃ surfaces, and thus, these species cannot be ignored. To study the effect of near-surface hydrogen species on the surface chemistry of metal oxides, two important reactions were considered. The first is H₂ dissociation, which is an important process in catalytic hydrogenation (and dehydrogenation) reactions. The second is CO₂ hydrogenation, which is a representative hydrogenation reaction. It was found that the presence of near-surface hydrogen species results in modulation of the surface electronic and chemical properties of β-Ga₂O₃(100), leading to a change in the preferred pathway for these surface chemical reactions. These findings emphasize the crucial role of near-surface hydrogen species in tuning the selectivity of chemical reactions on metal oxide surfaces. This perspective has not been identified thus far, to the best of our knowledge, but is consistent with previously reported experimental results in many aspects.