Efficient synthesis of polycyclic dispirooxindoles via domino Diels–Alder cyclodimerization reaction

Three-component reactions of 4-cyanopyridine or ethyl isonicotinate with electron-deficient alkynes and isatins in dimethoxyethane at room temperature afforded spiro[3H-indole-3,2′-[2H,9aH-pyrido[2,1-b][1,3]oxazine] derivatives. Alternately, the similar three-component reaction at elevated temperature resulted in polycyclic dispirooxindole derivatives. The reaction mechanism is believed to involve sequential generation and cycloaddition of Huisgen's 1,4-dipole, and Diels–Alder cyclodimerization reaction. The similar three-component reactions containing acenaphthenequinone and phenanthrenequinone also afforded corresponding polyheterocyclic derivatives.     

含硼杂原子Na-B-ZSM-5分子筛对甲醇脱氢制甲醛反应的催化性能

以白炭黑为硅源、硼酸为硼源、NaOH为碱源、四丙基溴化铵(TPABr)和1,6-己二胺(HMDA)混合模板剂,采用水热合成法制备含硼杂原子Na-B-ZSM-5分子筛,用XRD、SEM、FT-IR、UV-vis、11B MAS NMR、NH3-TPD等方法对其进行表征。在连续流动常压固定床反应器上评价Na-B-ZSM-5分子筛对甲醇脱氢制甲醛反应的催化性能,考察n(Si)/n(B)、n(Na2O)/n(SiO2)、晶化温度和晶化时间等制备参数以及反应温度和质量空速等工艺参数对催化性能的影响。结果表明,硼进入了分子筛的骨架结构中,存在与B酸中心有关的骨架四配位硼和与L酸中心有关的骨架三配位硼,Na-B-ZSM-5分子筛含有较多的弱酸位和少量的中强酸位。催化剂的最佳制备参数为n(Si)/n(B)比值为7.5、n(Na2O)/n(SiO2)比值为0.14、晶化温度170℃、晶化时间48 h。Na-B-ZSM-5(7.5)分子筛在反应温度550℃、质量空速1.85 h-1的反应条件下对甲醇的转化率为62.97%,甲醛的选择性为68.86%。     

A Theoretical Study on the Structure,Intramolecular Interactions,and Detonation Performance of Hydrazinium Dinitramide

The structures of hydrazinium dinitramide (HDN) in the gas phase and in aqueous solution have been studied at different levels of theory by using quantum chemistry. The intramolecular hydrogen‐bond interactions in HDN were studied by employing the quantum theory of atoms in molecules (QTAIM), as well as those in ammonium dinitramide (ADN), hydrazinium nitroformate (HNF), and ammonium nitroformate (ANF) for comparison. The results showed that HDN possessed the strongest hydrogen bonds, with the largest hydrogen‐bond energy (?47.95 kJ mol^?1) and the largest total hydrogen‐bond energy (?60.29 kJ mol^?1). In addition, the charge transfer between the cation and the anion, the binding energy, the energy difference between the frontier orbitals, and the second‐order perturbation energy of HDN were all the largest among the investigated compounds. These strongest intramolecular interactions accounted for the highest decomposition temperature of HDN among all four compounds. The IR spectra in the gas phase and in aqueous solution were very different and showed the significant influence of the solvent. The UV spectrum showed the strongest absorption at about 253 nm. An orbital‐interaction diagram demonstrated that the transition of electrons mainly happened inside the anion of HDN. The detonation velocity (D=8.34 km s^?1) and detonation pressure (P=30.18 GPa) of HDN were both higher than those of ADN (D=7.55 km s^?1 and P=24.83 GPa). The composite explosive HDN/CL‐20 with the weight ratio w_CL?20/w_HDN=0.388:0.612 showed the best performance (D=9.36 km s^?1, P=39.82 GPa), which was close to that of CL‐20 (D=9.73 km s^?1, P=45.19 GPa) and slightly better than that of the composite explosive ADN/CL‐20 (w_CL?20/w_ADN=0.298:0.702, D=9.34 km s^?1, P=39.63 GPa).     

Kinetically rate-determining step modulation by metal—support interactions for CO oxidation on Pt/CeO2

Science China Chemistry - Rational design and performance promotion are eternal topics and ultimate goals in catalyst preparation. In contrast, trial—and—error is still the common...     

Simultaneous analysis of six inorganic anions in urine by double-suppress ion-exchange chromatography

This study is aimed to establish a simple, rapid, and accurate ion chromatography approach for the simultaneous detection of six inorganic anions in urine. Various performance parameters affecting the determination of anions were optimized, including the selection of sample protein precipitation agent, eluent, and flow rate. The final eluent was 3.6 mmol/L sodium carbonate and 12% isopropanol with a flow rate of 0.6 mL/min. Acetonitrile was used for pretreatment to precipitate proteins, and the volume ratio of urine to acetonitrile was 1:4. The correlation coefficient of the target anion calibration curve ranged from 0.9973 to 0.9999. The limit of detection ranged from 1.50 to 12.0 μg/L, and the method detection limit ranged from 15.0 to 120 μg/L. The standard recovery rate for low, medium, and high concentrations ranged from 90 to 110%. The inter-day and intra-day relative standard deviations were <5%. The method has high accuracy and good reproducibility and is suitable for the separation and determination of anions in urine.     

CuS nanodots-loaded biohybrid magnetic helical microrobots with enhanced photothermal performance

Magnetic helical microrobots swimming at low Reynolds numbers have attracted much interest because of their great potentials for biomedical applications. However, to endow them with sophisticated function integration toward targeted disease treatment still remains a major challenge. Here, we proposed a novel strategy of using Spirulina scaffolds to fabricate biohybrid magnetic helical microrobot (BMHM) with enhanced photothermal performance to fight against cancer cells and pathogenic bacteria. For the first time, CuS nanodots were densely and uniformly loaded intracellularly inside Spirulina cells after permeabilization, and Fe₃O₄ nanoparticles were subsequently deposited on the cell walls for magnetization. The BMHMs could be actuated forward at a high velocity and flexibly steered under rotating magnetic fields. Rapid and great photothermal temperature raise with robust cycling stability was achieved under 808 nm near-infrared laser irradiation. The BMHMs showed good biocompatibility with minor toxicity to HeLa cancer cells and Escherichia coli bacteria. Moreover, significant photothermal performance was further verified via a series of experiments for anticancer therapy and bacteria killing. Because of the remarkable features and facile cost-effective fabrication, the BMHMs demonstrated great potentials as an integrated microrobot platform for future anticancer and antibacteria applications.     

Reduction of Dimerization Tendency Due to the Decrease in Hybridization Index by Inclusion of 4s and 4p Semicore States as Valence States in Mon (n=2-18) Clusters: A First-Principles Study

Owing to the unique structural, electronic, and physico-chemical properties, molybdenum clusters are expected to play an important role in future nanotechnologies. However, their ground states are still under debate. In this study, the crystal structure analysis by particle swarm optimization (CALYPSO) approach is used for the global minimum search, which is followed by first-principles calculations, to detect an obvious dimerization tendency in Mo\begin{document}$ _n $\end{document} (\begin{document}$ n $\end{document} = 2\begin{document}$ - $\end{document}18) clusters when the 4s and 4p semicore states are not regarded as the valence states. Further, the clusters with even number of atoms are usually magic clusters with high stability. However, after including the 4s and 4p electrons as valence electrons, the dimerization tendency exhibits a drastic reduction because the average hybridization indices \begin{document}$ H_{ \rm{sp}} $\end{document}, \begin{document}$ H_{ \rm{sd}} $\end{document}, and \begin{document}$ H_{ \rm{pd}} $\end{document} are reduced significantly. Overall, this work reports new ground states of Mo\begin{document}$ _n $\end{document} (\begin{document}$ n $\end{document} = 11, 14, 15) clusters and proves that semicore states are essential for Mo\begin{document}$ _n $\end{document}     

Single-crystal structure of two-dimensional organic framework based on donor-acceptor interactions with charge-transfer effect

Two charge-transfer single crystals induced by donor-acceptor interactions were obtained. The presence of different solvent molecules led to 1D(linear) or 2D self-assembly modes. More interestingly, the 2 D organic framework, a layer-by-layer 2D organic framework single crystal, showed a stronger charge-transfer effect than the 1D cocrystal.