Facile,Highly Stereoselective Synthesis of Cyclopropyl Benzoimidazoles via Cyclopropanation of Olefin with Arsonium Ylides

A facile and highly stereoselective methodology for the preparation of highly functionalized trans-1,2-cyclopropanes containing benzoimidazolyl, cyano, aryl, and carbonyl groups 3 is described. Arsonium bromides 2 reacted with electron-deficient olefins 1 in the presence of KF·2H₂O to provide 3 exclusively with high stereoselectivity in moderate to good yields.     

Cyclometalated Ruthenium Complexes of 1,2,3-Triazole-containing Ligands: Synthesis, Structural Studies, and Electronic Properties

Six bis‐tridentate and two tris‐bidentate cyclometalated ruthenium complexes with a 1,2,3‐triazole‐containing ligand have been prepared and characterized. Single‐crystal X‐ray analyses of complexes [(MeOptpy)Ru(Budtab)](PF₆) and [(Mebip)Ru(Budtab)](PF₆) are presented, where MeOptpy is 4′‐p‐methoxyphenyl‐2,2′:6′,2′′‐terpyridine, Budtab is the 2‐deprotonated form of 1,3‐di(N‐n‐butyl‐1,2,3‐triazol‐4‐yl)benzene, and Mebip is bis(N‐methyl‐benzimidazolyl)pyridine. The electronic properties of these complexes are probed by spectroscopic and electrochemical analyses. Time‐dependent density functional theory calculations have been performed to assist the assignment of the absorption spectra.     

Copolymers of dicyclopentadiene and tricyclopentadiene

Series of copolymers of dicyclopentadiene and tricyclopentadiene have been prepared by ringopening metathesis polymerization (ROMP) using a catalytic system of [W(=N-phenyl) (2,6-dimethyl phenolate)₄]/n-BuLi. Due to the presence of double bonds, the polymers obtained from ROMP are unstable. Thus the hydrogenation reaction is carried out after ROMP using a catalyst of bis(2,4-pentanediono)nickel/triisobutylaluminium. The polymers obtained were characterized by means of ¹H NMR; the results show an agreement with the proposed structure. Glass transition temperature T _g of the polymers are modulated by the feed mole ratio of dicyclopentadiene and tricyclopentadiene. With the increasing of tricyclopentadiene content, the T _g of the polymers before hydrogenation increases from 153 to 256°C, and the T _g of the polymers after hydrogenation increases from 106 to 188°C. In addition, the different ratio of dicyclopentadiene and tricyclopentadiene in polymer main chains offers different packing patterns to the structure of the copolymers, and leads to their different free volumes and occupied volumes.     

Quality evaluation of traditional Chinese medicines based on fingerprinting

The usage of traditional Chinese medicines has expanded globally, but the data about authentication, efficacy, and safety is far from sufficient to meet the criteria supporting their use worldwide due to complexity in the composition. Fingerprinting describes integral characterization and reflects interactive aspects of complex components; therefore, it can offer the possibility of evaluating quality of traditional Chinese medicines following the overall principle. Chemometric techniques introduce multivariate analytical methods into fingerprinting to obtain more information that is useful, which is consistent with the holistic thought and plays an important role in research on the substantial basis. In this review, we will start with three aspects to expound the quality evaluation of traditional Chinese medicines based on fingerprints. The analytical techniques used in developing fingerprints including chromatographic methods, spectroscopic methods, and capillary electrophoresis are introduced. Strategies for fingerprints analysis usually based on chemometric methods including unsupervised and supervised pattern recognition are described. Applications of fingerprints for multi‐component quantification, quality control, screening of bioactive components, and fingerprint‐efficacy relationship study are also outlined. Finally, we propose challenges and future perspectives of fingerprints in quality evaluation to promote the development of modernization and internationalization of traditional Chinese medicines.     

Preparation of single-layer antireflective SiO2 coating with broadband transmittance using PEG-modified sol–gel method

Adding polyethylene glycol (PEG) with different molecular weights, a usual acid-catalyzed sol–gel was modified to prepare single-layer antireflective SiO₂ coatings with high and broadband transmittance and relatively better hardness. The test results of atomic force microscope and field emission scanning electron microscope show that the addition of PEG significantly affects the porosity and surface morphology of the coating layer. Due to the addition of PEG, the surface of the coatings presents groove-like and their porosity is increased, both of which contribute to the increase in transmittance. In the case of same PEG mass, PEG4000 modified coating has higher porosity and higher transmittance than PEG1000 modified one. In the present paper, the reflectance of samples for both sides was tested by ultraviolet–visible–near-infrared spectrophotometer (LAMBDA 950). The best coating’s reflectance can be decreased below 5 % from 460 to 1,740 nm. The transmittance peak value of the substrate is 90.6 % and its average value is 90.0 %, while the peak value of the best coating can reach up to 99.4 % and its average value is 95.5 % which increased by 5.5 % from wavelength of 325 to 1,000 nm. Hardness measurements show that the coatings have relatively better hardness.     

一个不等式的拓广

Kantorovich 不等式的推广文〔4〕给出了x′Ay y′A~(-1)x/(x′xyy′)的上界,其中A是n 阶实正定阵,x、y 是n 维非零实向量。本文给出x′Ay y′A~(-1)x/(x′xy′y)的上界和下界,其中A 是任何n×m 实矩阵,A~(-1)是A 的广义加号逆,x、y 分别是n 维和m 维非零实向量。     

Surface thermodynamics and adhesion forces governing bacterial transmission in contact lens related microbial keratitis

Contact lens induced microbial keratitis results from bacterial transmission from one surface to another. We investigated the adhesion forces of Pseudomonas aeruginosa, Staphylococci and Serratia to different contact lenses, lens cases and corneal surfaces using AFM, and applied a Weibull analysis on these adhesion forces to calculate bacterial transmission probabilities from lens case to corneas with a contact lens as an intermediate. Also a new surface thermodynamic parameter was introduced, the interfacial free energy of transmission, which in essence compares the interfacial free energies of bacterial adhesion, calculated from measured contact angles with liquids on the donating and receiving surfaces in the transmission process. Bacterial adhesion forces were generally strongest among all eight strains for the lens case (-6.5 to -12.0 nN) and corneas (-3.5 to -11.5 nN), while contact lenses (-0.6 to -13.1 nN) exerted slightly smaller adhesion forces. Consequently, bacterial transmission from lens case to contact lens yielded a smaller contribution in the final transmission than from contact lens to cornea. Bacterial transmission probabilities as derived from force analyses were higher when the interfacial free energies of transmission were more negative, which is in line with surface thermodynamic principles. Therewith this parameter could provide useful in analyzing other bacterial transmission phenomena between donating and receiving surfaces as well.     

Thin film assembly of spider silk-like block copolymers

We report the self-assembly of monolayers of spider silk-like block copolymers. Langmuir isotherms were obtained for a series of bioengineered variants of the spider silks, and stable monolayers were generated. Langmuir-Blodgett films were prepared by transferring the monolayers onto silica substrates and were subsequently analyzed by atomic force microscopy (AFM). Static contact angle measurements were performed to characterize interactions across the interface (thin film, water, air), and molecular modeling was used to predict 3D conformation of spider silk-like block copolymers. The influence of molecular architecture and volume fraction of the proteins on the self-assembly process was assessed. At high surface pressure, spider silk-like block copolymers with minimal hydrophobic block (f(A) = 12%) formed oblate structures, whereas block copolymer with a 6-fold larger hydrophobic domain (f(A) = 46%) formed prolate structures. The varied morphologies obtained with increased hydrophobicity offer new options for biomaterials for coatings and related options. The design and use of bioengineered protein block copolymers assembled at air-water interfaces provides a promising approach to compare 2D microstructures and molecular architectures of these amphiphiles, leading to more rationale designs for a range of nanoengineered biomaterial needs as well as providing a basis of comparison to more traditional synthetic block copolymer systems.     

Energetic salts based on dipicrylamine and its amino derivative

Energetic salts based on dipicrylamine and its amino derivative were synthesized. All salts were fully characterized by multinuclear NMR spectroscopy ((1)H, (13)C), vibrational spectroscopy (IR), and elemental analysis. Ethylenediammonium di-DPA (DPA=dipicrylamine) and 1,3-diaminoguanidinium DPA were further confirmed by single-crystal X-ray diffraction. These salts exhibit reasonable physical properties, such as high densities (1.71-1.81 g cm(-3)), good thermal stabilities (T(d) =155-285 °C), and low solubilities in water. The impact sensitivity of 1-methyl-3,4,5-triamino-1,2,4-triazolium DPA is lower than that of 2,4,6-trinitrotoluene (TNT), and for some other energetic salts their impact sensitivities are comparable to that of TNT. Based on experimental densities and theoretical calculations carried out by using the Gaussian 03 suite of programs, all the salts have calculated detonation pressures (22.5-27.8 GPa) and velocities (7226-7917 m s(-1)) that exceed those of conventional TNT. The toxicities of these salts measured by luminescent bacteria toxicity tests are much lower than that of TNT, and two binary eutectic mixtures with melting points that fall between 70 and 100 °C were identified.     

Stress mechanism of pulsed laser-driven damage in thin film under nanosecond ultraviolet laser irradiation

An analytical model is derived to describe the stress mechanism in a thin film against the laser-induced damage threshold (LIDT) based on the thermal transfer equation. Different structures of high-reflection films at 355 nm are prepared to validate this model. LIDTs are found to have a linear relationship with stress. Furthermore, predictions from the simple model agree with the experiments.