Reactivity of Dicoordinated Stannylones (Sn0) versus Stannylenes (SnII): An Investigation Using DFT‐Based Reactivity Indices

The reactivity of dicoordinated Sn⁰ compounds, stannylones, is probed using density functional theory (DFT)‐based reactivity indices and compared with the reactivity of dicoordinated Sn^II compounds, stannylenes. For the former compounds, the influence of different types of electron‐donating ligands, such as cyclic and acyclic carbenes, stannylenes and phosphines, on the reactivity of the central Sn atom is analyzed in detail. Sn⁰ compounds are found to be relatively soft systems with a high nucleophilicity, and the plots of the Fukui function f^? for an electrophilic attack consistently predict the highest reactivity on the Sn atom. Next, complexes of dicoordinated Sn compounds with different Lewis acids of variable hardness are computed. In a first part, the double‐base character of stannylones is demonstrated in interactions with the hardest Lewis acid H⁺. Both the first and second proton affinities (PAs) are high and are well correlated with the atomic charge on the Sn atom, probing its local hardness. These observations are also in line with electrostatic potential plots that demonstrate that the tin atom in Sn⁰ compounds bears a higher negative charge in comparison to Sn^II compounds. Stannylones and stannylenes can be distinguished from each other by the partial charges at Sn and by various reactivity indices. It also becomes clear that there is a smooth transition between the two classes of compounds. We furthermore demonstrate both from DFT‐based reactivity indices and from energy decomposition analysis, combined with natural orbitals for chemical valence (EDA‐NOCV), that the monocomplexed stannylones are still nucleophilic and as reactive towards a second Lewis acid as towards the first one. The dominating interaction is a strong σ‐type interaction from the Sn atom towards the Lewis acid. The interaction energy is higher for complexes with the cation Ag⁺ than with the non‐charged electrophiles BH₃, BF₃, and AlCl₃.     

An integrated sample pretreatment platform for quantitative N-glycoproteome analysis with combination of on-line glycopeptide enrichment,deglycosylation and dimethyl labeling

Relative quantification of N-glycoproteomes shows great promise for the discovery of candidate biomarkers and therapeutic targets. The traditional protocol for quantitative analysis of glycoproteomes is usually off-line performed, and suffers from long sample preparation time, and the risk of sample loss or contamination due to manual manipulation. In this study, a novel integrated sample preparation platform for quantitative N-glycoproteome analysis was established, with combination of online N-glycopeptide capture by a HILIC column, sample buffer exchange by a N₂-assisted HILIC–RPLC interface, deglycosylation by a hydrophilic PNGase F immobilized enzymatic reactor (hIMER) and solid dimethyl labeling on a C18 precolumn. To evaluate the performance of such a platform, two equal aliquots of immunoglobulin G (IgG) digests were sequentially pretreated, followed by MALDI-TOF MS analysis. The signal intensity ratio of heavy/light (H/L) labeled deglycosylated peptides with the equal aliquots was 1.00 (RSD = 6.2%, n = 3), much better than those obtained by the offline protocol, with H/L ratio as 0.76 (RSD = 11.6%, n = 3). Additionally, the total on-line sample preparation time was greatly shortened to 160 min, much faster than that of offline approach (24 h). Furthermore, such an integrated pretreatment platform was successfully applied to analyze the two kinds of hepatocarcinoma ascites syngeneic cell lines with high (Hca-F) and low (Hca-P) lymph node metastasis rates. For H/L labeled Hca-P lysates with the equal aliquots, 99.6% of log 2 ratios (H/L) of quantified glycopeptides ranged from −1 to 1, demonstrating high accuracy of the developed sample preparation strategy. By triplicated analysis of glycopeptides and non-glycopeptides of Hca-F and Hca-P lysates, 43 up-regulated and 30 down-regulated (Hca-F/P) N-glycosylation sites, and 11 significantly changed N-glycoproteins were successfully quantified, and most of them were related to tumorigenesis and tumor metastasis. All these results demonstrate the developed integrated N-glycoprotein pretreatment platform is of great power for the accurate, precise and high-throughput analysis of N-glycoproteomes.     

水溶性配合物催化的稠油低温热裂解研究

在一种新型稠油低温裂解催化体系中合成了两个系列10个过渡金属配合物催化剂。该反应体系中水对原油热降解反应有一定的影响,合适的用量水/油(质量比)为0.3。部分合成水溶性催化剂180℃下对稠油热裂解具有明显的催化作用,催化剂N5的降凝作用效果最好,经催化水热降解改质反应后原油的凝点降低11.4℃;催化剂N2和N5的催化降黏效果较好,降黏率可达70%以上,催化剂N5的最佳用量为0.5%;热重分析和气相色谱分析显示原油热催化降解反应后轻质组分明显增加。     

Enhanced properties of phthalonitrile resins under lower curing temperature via complex curing agent

High curing temperature has been restricting the application and development of phthalonitrile resin. A complex curing agent containing melamine (ME) and ZnCl₂ was developed to promote the curing reaction of resorcinol‐based phthalonitrile resin (DPPH). The thermal stability of ME can be significantly enhanced via adding ZnCl₂, which was due to the interaction between ZnCl₂ and amino group in ME. Moreover, the activities of pristine ZnCl₂ and ME were improved via mixing, especially, the curing temperature for DPPH can be effectively reduced. Even at a curing temperature of 300°C, the 5% weight loss temperature of the resulting resin cured with complex curing agent still exceeded 500°C, which was much higher than those with pristine curing agents. In addition, the good long‐term oxidation stability and relatively low water absorption can also be obtained in the resins cured with novel curing agent. This work affords a facile route for designing high‐performance curing agent to improve the curing process of phthalonitrile resin.     

An experimental investigation on the low‐velocity impact behavior of 3D five‐directional braided composites

This paper presents an experimental study on the low‐velocity impact performance of 3D carbon/epoxy braided composite panels with different braiding parameters, which have the similar fiber volume fraction but different braiding angles (15°, 25°, and 35°). The low‐velocity impact tests were conducted at three different energy levels of 15, 30, and 45 J. Impact response of the panels was recorded and analyzed in terms of peak load, absorbed energy, time, and deflection at peak load. The images of damage samples taken from impacted sides and non‐impacted sides were evaluated for the damage area and failure patterns. Through analysis, they discovered that samples with bigger braiding angle sustained higher peak loads; moreover, the fiber was arranged more closely, and the shock resistance improved as the braiding angle is increasing. Copyright © 2014 John Wiley & Sons, Ltd.     

A Coordination Compound of Ge0 Stabilized by a Diiminopyridine Ligand

Reduction of the cationic Ge^II complex [dimpyrGeCl][GeCl₃] (dimpyr=2,6‐(ArN=CMe)₂NC₅H_3, Ar=2,6‐iPr₂C₆H₃) with potassium graphite in benzene affords an air sensitive, dark green compound of Ge⁰, [dimpyrGe], which is stabilized by a bis(imino)pyridine platform. This compound is the first example of a complex of a zero‐valent Group 14 element that does not contain a carbene or carbenoid ligand. This species has a singlet ground state. DFT studies revealed partial delocalization of one of the Ge lone pairs over the π*(C?N) orbitals of the imines. This delocalization results in a partial multiple‐bond character between the Ge atom and imine nitrogen atoms, a fact supported by the X‐ray crystallography and IR spectroscopy data.     

Twisted but Conjugated: Building Blocks for Low Bandgap Polymers

Here we report a novel twisted monomer based on a distorted C?C double bond for low bandgap conjugated copolymers. This new building block provides several unique characteristics when compared to classical planar systems such as high solubility, electron accepting ability, and isomeric tunability. The resulting copolymers exhibit broad absorption spanning both visible and near‐infrared regions leading to promising solar cell performance.     

Monolithically Integrated Spinel MxCo3−xO4 (M=Co,Ni, Zn) Nanoarray Catalysts: Scalable Synthesis and Cation Manipulation for Tunable Low‐Temperature CH4 and CO Oxidation

A series of large scale M_xCo_3?xO₄ (M=Co, Ni, Zn) nanoarray catalysts have been cost‐effectively integrated onto large commercial cordierite monolithic substrates to greatly enhance the catalyst utilization efficiency. The monolithically integrated spinel nanoarrays exhibit tunable catalytic performance (as revealed by spectroscopy characterization and parallel first‐principles calculations) toward low‐temperature CO and CH₄ oxidation by selective cation occupancy and concentration, which lead to controlled adsorption–desorption behavior and surface defect population. This provides a feasible approach for scalable fabrication and rational manipulation of metal oxide nanoarray catalysts applicable at low temperatures for various catalytic reactions.