Designable assembly of atomically precise Al4O4 cubane supported mesoporous heterometallic architectures

Heterometallic cluster-based framework materials are of interest in terms of both their porous structures and multi-metallic reactivity. However, such materials have not yet been extensively investigated because of difficulties in their synthesis and structural characterization. Herein, we reported the designable synthesis of atomically precise heterometallic cluster-based framework compounds and their application as catalysts in aldol reactions. By using the synergistic coordination protocol, we successfully isolated a broad range of compounds with the general formula, [Al₄M₄O₄(L)₁₂(DABCO)₂] (L = carboxylates; DABCO = 1,4-diazabicyclo[2.2.2]-octane; M²⁺ = Co²⁺, Mn²⁺, Zn²⁺, Fe²⁺, Cd²⁺). The basic heterometallic building blocks contain unprecedented main-group γ-alumina moieties and surrounding unsaturated transition metal centers. Interestingly, the porosity and interpenetration of these frameworks can be rationally regulated through the unprecedented strategy of increment of the metal radius in addition to general introduction of sterically bulky groups on the ligand. Furthermore, these porous materials are effective catalysts for aldol reactions. This work provides a catalytic molecular model platform with accurate molecular bonding between the supporters and catalytically active metal ions.

Mesoporous heterometallic architectures are designed by the incorporation of the Al₄O₄ cubane and interpenetration regulation.     

快速响应高压电源在KTP晶体极化反转中的应用研究

分析了KTP晶体电导率的特性,设计与研制出一种新型的高压脉冲放大器,可将任意信号发生器产生的信号线性放大,响应速度快,最高输出电压为4000V,最大输出电流为30mA,功率可达100W.用其在KTP晶体上进行多次极化反转实验,取得良好的实验结果.     

Facile Fabrication of 1-Methylimidazole/Cu Nanozyme with Enhanced Laccase Activity for Fast Degradation and Sensitive Detection of Phenol Compounds

Facile construction of functional nanomaterials with laccase-like activity is important in sustainable chemistry since laccase is featured as an efficient and promising catalyst especially for phenolic degradation but still has the challenges of high cost, low activity, poor stability and unsatisfied recyclability. In this paper, we report a simple method to synthesize nanozymes with enhanced laccase-like activity by the self-assembly of copper ions with various imidazole derivatives. In the case of 1-methylimidazole as the ligand, the as-synthesized nanozyme (denoted as Cu-MIM) has the highest yield and best activity among the nanozymes prepared. Compared to laccase, the K_m of Cu-MIM nanozyme to phenol is much lower, and the v_max is 6.8 times higher. In addition, Cu-MIM maintains excellent stability in a variety of harsh environments, such as high pH, high temperature, high salt concentration, organic solvents and long-term storage. Based on the Cu-MIM nanozyme, we established a method for quantitatively detecting phenol concentration through a smartphone, which is believed to have important applications in environmental protection, pollutant detection and other fields.     

Palladium-catalyzed hydrosilylation of ynones to access silicon-stereogenic silylenones by stereospecific aromatic interaction-assisted Si–H activation

Hydrosilylation is one of the most important reactions in synthetic chemistry and ranks as a fundamental method to access organosilicon compounds in industrial and academic processes. However, the enantioselective construction of chiral-at-silicon compounds via catalytic asymmetric hydrosilylation remained limited and difficult. Here we report a highly enantioselective hydrosilylation of ynones, a type of carbonyl-activated alkynes, using a palladium catalyst with a chiral binaphthyl phosphoramidite ligand. The stereospecific hydrosilylation of ynones affords a series of silicon-stereogenic silylenones with up to 94% yield, 20:1 regioselectivity and 98:2 enantioselectivity. The density functional theory(DFT) calculations were conducted to elucidate the reaction mechanism and origin of high degree of stereoselectivity, in which the powerful potential of aromatic interaction in this reaction is highlighted by the multiple C–H-π interaction and aromatic cavity-oriented enantioselectivitydetermining step during desymmetric functionalization of Si–H bond.     

Bioavailability Enhancement of Cepharanthine via Pulmonary Administration in Rats and Its Therapeutic Potential for Pulmonary Fibrosis Associated with COVID-19 Infection

Cepharanthine (CEP) has excellent anti-SARS-CoV-2 properties, indicating its favorable potential for COVID-19 treatment. However, its application is challenged by its poor dissolubility and oral bioavailability. The present study aimed to improve the bioavailability of CEP by optimizing its solubility and through a pulmonary delivery method, which improved its bioavailability by five times when compared to that through the oral delivery method (68.07% vs. 13.15%). An ultra-performance liquid chromatography tandem-mass spectrometry (UPLC-MS/MS) method for quantification of CEP in rat plasma was developed and validated to support the bioavailability and pharmacokinetic studies. In addition, pulmonary fibrosis was recognized as a sequela of COVID-19 infection, warranting further evaluation of the therapeutic potential of CEP on a rat lung fibrosis model. The antifibrotic effect was assessed by analysis of lung index and histopathological examination, detection of transforming growth factor (TGF)-β1, interleukin-6 (IL-6), α-smooth muscle actin (α-SMA), and hydroxyproline level in serum or lung tissues. Our data demonstrated that CEP could significantly alleviate bleomycin (BLM)-induced collagen accumulation and inflammation, thereby exerting protective effects against pulmonary fibrosis. Our results provide evidence supporting the hypothesis that pulmonary delivery CEP may be a promising therapy for pulmonary fibrosis associated with COVID-19 infection.     

New reactivities of deltaline analogs: an efficient O-demethylation at C-1 and an unusual extrusion of the C-14 atom

O-Demethylation at C-1 in the C₁₉-diterpenoid alkaloids is very challenging. In this paper, it was firstly observed that 10-OH group in deltaline (1) is a determining factor for the O-demethylation reaction. After removal of this hydroxyl group, 1-O-methyl group in the corresponding deltaline analogs can be readily removed by treatment with HBr–HOAc. Meanwhile, the C-14 atom in bromides 18 or 20 can be extruded under basic condition probably via a sequence, including Grob fragmentation, aerobic oxidation, deformylation, and S_N2 nucleophilic substitution, to give enone 21 (70%) and oxetane 22 (14%). The structure of compound 22 was confirmed by X-ray crystallographic analysis of its derivative 21.     

Polystyrene-bound diethanolamine based ionic liquids for chemical fixation of CO2

Polystyrene-bound diethanolamine based ionic liquids (PS-DHEEAB and PS-THEAB) were synthesized and applied for the chemical fixation of CO₂ into cyclic carbonates without any additional co-catalyst and solvent. The effect of the catalysts with different number of hydroxyl group in the cation of the IL on the reaction was systematically investigated. Highest activity and selectivity were achieved in the presence of polystyrene supported diethanolamine ethyl bromide (PS-DHEEAB) in comparison with other catalysts employed. The catalyst was tough in stability and also found to be extended to a variety of terminal epoxides and aziridines. The relationship between high catalytic reactivity and the –OH functional groups was proposed.