Syntheses of 2,4-disubstituted 1,3,5-triazapentadienyl ligands having two guanidinato moieties and their use in the isolation of copper(I) complexes

2,4-N,N'-Disubstituted 1,3,5-triazapentadienyl ligands as their lithium salts [Li{(N(R)C(R'))2N}]2 [where R = SiMe3 here and hereafter and R' = dimethylamino (1) or 1-piperidino (2)] were synthesized via the reactions of LiN(SiMe3)2 with 2 equiv of the alpha-hydrogen-free carbonitrile dimethylcyanamide or 1-piperdinecarbonitrile and used in the isolation of the two-coordinate copper(I) complexes [Cu{(N(R)C(R'))2N}]2 [R' = dimethylamino (3) and 1-piperidino (4)]. Complex 2 features a twisted W-shaped ligand backbone in the solid state. Complexes 3 and 4 show an unusual 12-membered ring dinuclear copper( I) triazapentadienyl and a less expressed ability to form a stable delocalized triazapentadienyl system.     

Diruthenium(II,III) bis(tetramethyl-1,3-benzenedipropionate) as a novel catalyst for tert-butyl hydroperoxide oxygenation

The reaction of Ru2(OAc)4Cl with 2.2 equiv of H2esp (esp = alpha,alpha,alpha',alpha'-tetramethyl-1,3-benzenedipropionate) resulted in a new compound, Ru2(esp)2Cl (1), that is soluble in organic media. 1 is an active catalyst for the oxygenation of organic sulfides by tert-butyl hydroperoxide (TBHP) in both an acetonitrile solution or neat (solvent-free) conditions. Solvent-free reactions display the quantitative utility of TBHP and hence excellent chemical selectivity for sulfoxide formation.     

超疏水表面改善铝基材料的抗海水腐蚀性能

通过聚乙烯亚胺与十四酸的反应,在铝表面构建稳定的超疏水膜。以X射线衍射,原子力显微镜,扫描电镜,接触角测量仪等手段表征超疏水表面的形成机制与表面结构特征,并利用电化学阻抗方法研究了超疏水表面对铝在海水中的腐蚀行为的影响。结果表明,在铝表面形成了一层近似珊瑚状的超疏水膜,海水的接触角大于150°。通过电化学阻抗图谱测试空白样与试样的耐腐蚀性能,表明这种特殊的表面结构的超疏水膜的确降低了铝在海水中的腐蚀速率。     

Cu-Doped MoSi2N4 Monolayer as a Potential NH3 Sensor

Cu doped MoSi₂N₄ monolayer (Cu-MoSi₂N₄) was firstly proposed to analyze adsorption performances of common gas molecules including O₂, N₂, CO, NO, NO₂, CO₂, SO₂, H₂O, NH₃ and CH₄ via density functional theory (DFT) combining with non-equilibrium Green's function (NEGF). The electronic transport calculations indicate that Cu-MoSi₂N₄ monolayer has high sensitivity for CO, NO, NO₂ and NH₃ molecules. However, only NH₃ molecule adsorbs on the Cu-MoSi₂N₄ monolayer with moderate strength (−0.55 eV) and desorbs at room temperature (2.36×10⁻³ s). Thus, Cu-MoSi₂N₄ monolayer is demonstrated as a potential NH₃ sensor.     

Development of a general separation strategy by countercurrent chromatography using sanshools from Zanthoxylum bungeanum oleoresin as a case study

Three kinds of sanshools were separated from Zanthoxylum bungeanum oleoresin by high-speed countercurrent chromatography. Sanshools are a series of amide compounds extracted from the Zanthoxylum bungeanum. Due to similar structures, polarities, and dissociation constants, it was challenging to select an appropriate solvent system for their complete separation by countercurrent chromatography. To address this challenge, a solvent-system-selection strategy was proposed to identify a relatively suitable solvent system. Additionally, a separation procedure incorporating multi-elution modes selection was established to separate similar compounds in a logical order. Ultimately, a solvent system comprising n-hexane:ethyl acetate:methanol:water in a ratio of 19:1:1:5.67 was selected. Three amide compounds with high purity were obtained through the use of recycling elution mode to improve separation resolution: hydroxy-ε-sanshool (8.4 mg; purity: 90.64%), hydroxy-α-sanshool (326.4 mg; purity: 98.96%), and hydroxy-β-sanshool (71.8 mg; purity: 98.26%) were obtained from 600 mg sanshool crude extract. The summarized solvent-system-selection strategy and separation procedure incorporating multi-elution modes may instruct countercurrent chromatography users, particularly novices, seeking to separate compounds with highly similar chemical properties.     

Facile synthesis of spherical covalent organic frameworks for enrichment and quantification of aryl organophosphate esters in mouse serum and tissues

Here, an imine-linked-based spherical covalent organic framework (COF) was prepared at room temperature. The as-synthesized spherical COF served as an adsorbent in dispersive solid-phase extraction (dSPE), by its virtue of great surface area (1542.68 m²/g), regular distribution of pore size (2.95 nm), and excellent stability. Therefore, a simple and high-efficiency dispersive solid phase extraction method based on a spherical COF coupled with high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) was established to determine aryl organophosphate esters in biological samples. This approach displayed favorable linearity in the range of 10.0–1000.0 ng/L (r > 0.9989), a high signal enhancement factor (58.8–181.8 folds) with low limits of detection (0.3–3.3 ng/L). Moreover, it could effectively eliminate complex matrix interference to accurately extract seven aryl organophosphate esters from mouse serum and tissue samples with spiked recoveries of 82.0%–117.4%. The as-synthesized spherical COF has been successfully applied in sample preparation. The dSPE-HPLC-MS/MS method based on a spherical COF has potential application to study the pollutants' metabolism in vivo.     

Matrix solid-phase dispersion combined with micro-fractionation bioactivity evaluation screening polymethoxylated flavones from Citrus peels

Polymethoxyflavones were a unique class of natural and safe flavonoids containing two or more methoxy groups, which were also the most abundant edible part in Citrus peel. The optimum condition in the process of selective extraction of polymethoxylated flavones from Citrus peel by matrix solid-phase dispersion (MSPD) was as follows: SBA-15 as adsorbent, ethyl acetate as eluent, the mass ratio of adsorbent to sample 1:1, and the mixture of sample and adsorbent was ground for 3 min. Twelve antioxidants were successfully screened by micro-fractionation bioactivity evaluation assay, in which four of them were flavonoid glycosides, seven of them were polymethoxylated flavones, and one was phenylpropanoid. 1-sinapoly-β-D-glucopyranoside (1) was reported for the first time in Citrus peel. And antioxidant capacity of 1-sinapoly-β-D-glucopyranoside, 5, 7, 8, 3′, 4′, 5′-hexamethoxyflavone (6), hexamethoxyflavone (11), and 5, 6, 7, 4′-tetramethoxyflavone (7) were reported for the first time. Nobiletin (compound 8), 3, 5, 6, 7, 8, 3′, 4′-heptamethoxyflavone (9) and tangeretin (10) were isolated and purified by countercurrent chromatography combined with preparative liquid chromatography. Antioxidant activity evaluation indicated that the three isolated polymethoxylated flavones owned similar antioxidant activity. This study indicated that MSPD combined with micro-fractionation bioactive evaluation was efficient in screening bioactive compounds for rapid extraction and effective pinpointing bioactive substances in natural products.     

Anticancer Gold(III) Porphyrins Target Mitochondrial Chaperone Hsp60

Identification of the molecular target(s) of anticancer metal complexes is a formidable challenge since most of them are unstable toward ligand exchange reaction(s) or biological reduction under physiological conditions. Gold(III) meso‐tetraphenylporphyrin ( gold‐1 a ) is notable for its high stability in biological milieux and potent in vitro and in vivo anticancer activities. Herein, extensive chemical biology approaches employing photo‐affinity labeling, click chemistry, chemical proteomics, cellular thermal shift, saturation‐transfer difference NMR, protein fluorescence quenching, and protein chaperone assays were used to provide compelling evidence that heat‐shock protein 60 (Hsp60), a mitochondrial chaperone and potential anticancer target, is a direct target of gold‐1 a in vitro and in cells. Structure–activity studies with a panel of non‐porphyrin gold(III) complexes and other metalloporphyrins revealed that Hsp60 inhibition is specifically dependent on both the gold(III) ion and the porphyrin ligand.     

Hawking Radiation of Spin-3/2 Particles from Kerr Black Hole

By using dimensional reduction and consistent anomaly method, we calculate the Hawking flux of the spin- 3/2 field in the Kerr black hole background. The results confirm that the Hawking radiation doesn’t depends on the detail of the fields living near the horizon, at least at the semi-classical level. The Hawking temperature is an universality character of black hole which only depends on the information of the horizon. Our calculation agrees with earlier results obtained by the WKB/tunneling method (Yale and Mann, Phys. Lett. B 673(2), 168–172, 2009).