Single electron transfer‐living radical polymerization of methyl methacrylate catalyzed by ytterbium powder

Zerovalent ytterbium (Yb) powder is firstly used as a catalyst in single electron transfer‐living radical polymerization of methyl methacrylate initiated by carbon tetrachloride in N, N‐dimethylformamide (DMF) and dimethyl sulfoxide, respectively. Polymerization proceeds in a “living”/controlled way as evidenced by kinetic studies and chain extension results, producing well‐defined polymers with controlled degree of polymerization and narrow molecular weight distribution. The apparent activation energy of polymerization in DMF is accounted to be 36.2 kJ/mol, and the energy of equilibrium state is calculated to be 13.9 kJ/mol. An increase in the concentration of Yb(0) yields a higher monomer conversion. It is observed that polymerization rate experiments a rapid increase in the presence of more polar solvent water, and increasing in the content of H₂O results in an increase in the apparent rate constant of polymerization, and a decrease in the molecular weight distribution. The reaction rate and molecular weight increase along with the decrease of DMF content. The effect of Yb(0) powder content, different ligands and concentration of initiator on the polymerization is also investigated. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Identification of reducing and nonreducing neutral carbohydrates by laser‐enhanced in‐source decay (LEISD) MALDI MS

In this work, laser‐enhanced in‐source decay (LEISD) technique of matrix‐assisted laser desorption/ionization Fourier transform ion cyclotron resonance mass spectrometry (MALDI‐FT‐ICR‐MS) was used to distinguish reducing and nonreducing carbohydrates. Interestingly, easier cleavage of (1 → 2)‐linked glycosidic bonds for nonreducing carbohydrates containing D‐fructofuranosyl units was observed in MALDI‐FT‐ICR‐MS, which was in agreement with the result of theoretical calculation by the software package Gaussian 09. Importantly, no cross‐ring cleavage of fructofuranosyl residues was detected in the LEISD spectra of nonreducing carbohydrates. LEISD method therefore offers an attractive alternative for fast and efficient differentiation of reducing and nonreducing carbohydrates, and the positions of nonreducing monosaccharide residues in a carbohydrate chain could be easily speculated. Copyright © 2013 John Wiley & Sons, Ltd.     

Mono‐ and Dinuclear Phosphorescent Rhenium(I) Complexes: Impact of Subcellular Localization on Anticancer Mechanisms

Elucidation of relationship among chemical structure, cellular uptake, localization, and biological activity of anticancer metal complexes is important for the understanding of their mechanisms of action. Organometallic rhenium(I) tricarbonyl compounds have emerged as potential multifunctional anticancer drug candidates that can integrate therapeutic and imaging capabilities in a single molecule. Herein, two mononuclear phosphorescent rhenium(I) complexes ( Re1 and Re2 ), along with their corresponding dinuclear complexes ( Re3 and Re4 ), were designed and synthesized as potent anticancer agents. The subcellular accumulation of Re1–Re4 was conveniently analyzed by confocal microscopy in situ in live cells by utilizing their intrinsic phosphorescence. We found that increased lipophilicity of the bidentate ligands could enhance their cellular uptake, leading to improved anticancer efficacy. The dinuclear complexes were more potent than the mononuclear counterparts. The molecular anticancer mechanisms of action evoked by Re3 and Re4 were explored in detail. Re3 with a lower lipophilicity localizes to lysosomes and induces caspase‐independent apoptosis, whereas Re4 with higher lipophilicity specially accumulates in mitochondria and induces caspase‐independent paraptosis in cancer cells. Our study demonstrates that subcellular localization is crucial for the anticancer mechanisms of these phosphorescent rhenium(I) complexes.     

An Atomically Precise Au10Ag2 Nanocluster with Red–Near‐IR Dual Emission

A red–near‐IR dual‐emissive nanocluster with the composition [Au₁₀Ag₂(2‐py?C≡C)₃(dppy)₆](BF₄)₅ ( 1 ; 2‐py?C≡C is 2‐pyridylethynyl, dppy=2‐pyridyldiphenylphosphine) has been synthesized. Single‐crystal X‐ray structural analysis reveals that 1 has a trigonal bipyramidal Au₁₀Ag₂ core that contains a planar Au₄(2‐py?C≡C)₃ unit sandwiched by two Au₃Ag(dppy)₃ motifs. Cluster 1 shows intense red–NIR dual emission in solution. The visible emission originates from metal‐to‐ligand charge transfer (MLCT) from silver atoms to phosphine ligands in the Au₃Ag(dppy)₃ motifs, and the intense NIR emission is associated with the participation of 2‐pyridylethynyl in the frontier orbitals of the cluster, which is confirmed by a time‐dependent density functional theory (TD‐DFT) calculation.     

Determination of arsenic species in Solanum Lyratum Thunb using capillary electrophoresis with inductively coupled plasma mass spectrometry

A simple and highly efficient interface to couple capillary electrophoresis with inductively coupled plasma mass spectrometry by a microflow polyfluoroalkoxy nebulizer and a quadruple ion deflector was developed in this study. By using this interface, six arsenic species, including arsenite, arsenate, monomethylarsonic acid, dimethylarsinic acid, arsenobetaine, and arsenocholine, were baseline‐separated and determined in a single run within 11 min under the optimized separation conditions. The instrumental detection limit was in the range of 0.02–0.06 ng/mL for the six arsenic compounds. Repeatability expressed as the relative standard deviation (n = 5) of both migration time and peak area were better than 2.5 and 4.3% for six arsenic compounds. The proposed method, combined with a closed‐vessel microwave‐assisted extraction procedure, was successfully applied for the determination of arsenic species in the Solanum Lyratum Thunb samples from Anhui province in China with the relative standard deviations (n = 5) ≤4%, method detection limits of 0.2–0.6 ng As/g and a recovery of 98–104%. The experimental results showed that arsenobetaine was the main speciation of arsenic in the Solanum Lyratum Thunb samples from different provinces in China, with a concentration of 0.42–1.30 μg/g.     

Analysis of FT-IR spectra of dicyclopentadienyl (bis-substituted cyclopentadienyl) dithiocyano of titanium, zirconium and hafnium

The FT-IR spectra of 18 (R-Cp)2M(NCS)2 were measured. The M-Cp, M-NCS (M=Ti, Zr, Hf) and other vibration modes were reasonably assigned. All complexes of (R-Cp)2M(NCS)2 determined in this paper are bonded by N-M, and the absorption of upsilon(s)(M-Cp)(A1) (M=Ti, Zr and Hf) vibration all appear in 365 cm(-1) or so, while upsilon(as)(M-Cp)(B) appear successively around 420, 350 and 320 cm(-1) in order of Ti, Zr and Hf. The influence of the center metal atoms and the substituents on cyclopentadienyl upon the spectra was discussed. It is mainly in far infrared region that center metal atoms influence upon the infrared spectra. The influence of the substituents to cyclopentadienyling upon its vibration is not significant. Only between 1500 and 1480 cm(-1) did a new absorbing peak appear due to the introduction of substituents to activate upsilon(CC) vibration.     

一种新型固体酸的制备及其在二（1-萘）甲烷加氢裂解中的催化性能

煤直接液化制取轻质燃料油和重要化学品是实现煤炭资源高效洁净利用的有效途径。煤液化的关键是在适当的温度、氢压、溶剂和催化剂存在的条件下,通过加氢裂解反应使连接煤中有机质大分子结构单元的较弱的桥键断裂生成可作为液体燃料的有机小分子,经后续的精细分离得到高附加值有机化学品和制备高性能炭材料前驱体,进而实现煤炭资源的高效利用。传统的煤液化工艺反应条件苛刻,需要高温和高氢压,导致能耗大和设备成本较高。酸性催化剂可使煤结构中的桥键在远低于煤热解反应的温度下断裂,并可有效除去煤中的杂原子,大幅提高液化油收率,因此酸性催化剂得到许多研究者关注。液体酸,如三氟甲磺酸、氟硼酸以及金属卤化物熔盐等均相酸性催化剂是煤液化工艺中常用的催化剂。虽然这些催化剂具有催化效率高和不易失活等优点,但大多数均相催化剂难以回收和再生,生产成本高,设备腐蚀性大,环境污染严重,因此在实际应用中受到限制。固体酸是具有广泛工业应用前景的环境友好催化剂,因而对固体酸的研究具有重要意义。本研究将液体三氟甲磺酸(TFMSA)通过浸渍吸附法负载到酸化的凹凸棒土(ATA)上制备了一种新型固体酸催化剂 TFMSA/ATA,并在相同条件下制备了 TFMSA/g-Al2O3和 TFMSA/ZSM-5作为对比。对TFMSA/ATA进行了透射电镜、傅里叶变换红外光谱、X射线光电子能谱、X射线衍射、N2吸附以及 NH3程序升温脱附表征。结果表明, TFMSA有效负载于 ATA载体表面及孔隙中,未发现明显的团聚,载体与活性组分之间存在较强的相互作用;另外, TFMSA/ATA上出现超强酸位点,说明 TFMSA/ATA具有超强酸性。以二(1-萘)甲烷加氢裂解作为探针反应考察了 TFMSA/ATA对 Car–Calk桥键断裂的催化活性。结果表明,二(1-萘)甲烷在 N2气氛和甲醇溶剂中选择性地加氢裂解,仅得到萘和1-甲基萘,未检测到加氢产物,且产物萘的收率明显高于1-甲基萘的收率,说明 TFMSA/ATA对二(1-萘)甲烷选择性加氢裂解和由此产生的1-甲基萘脱甲基反应有显著的促进作用。在相同反应条件下, TFMSA/ATA的活性明显高于 TFMSA/g-Al2O3和 TFMSA/ZSM-5,这是由于 TFMSA/ATA较大的比表面积以及载体 ATA与活性组分 TFMSA之间存在较强的相互作用有利于催化剂释放质子。由催化剂释放的质子优先进攻二(1-萘)甲烷中的取代位导致 Car–Calk键断裂是二(1-萘)甲烷加氢裂解的关键步骤。催化剂循环实验表明, TFMSA/ATA在循环使用4次后仍具有较高的催化活性,使用后催化剂酸性没有明显降低,说明 TFMSA/ATA具有良好的稳定性。     

An Alignment Medium for Measuring Residual Dipolar Couplings in Pure DMSO: Liquid Crystals from Graphene Oxide Grafted with Polymer Brushes

Residual dipolar couplings (RDCs) have attracted attention in light of their great impact on the structural elucidation of organic molecules. However, the effectiveness of RDC measurements is limited by the shortage of alignment media compatible with widely used organic solvents, such as DMSO. Herein, we present the first liquid crystal (LC) based alignment medium that is compatible with pure DMSO, thus enabling RDC measurements of polar and intermediate polarity molecules. The liquid crystals were obtained by grafting polymer brushes onto graphene oxide (GO) using free radical polymerization. The resulting new medium offers several advantages, such as absence of background signals, narrow line shapes, and tunable alignment. Importantly, this medium is compatible with π‐conjugated molecules. Moreover, sonication‐induced fragmentation can reduce the size of GO sheets. The resulting anisotropic medium has moderate alignment strength, which is a prerequisite for an accurate RDC measurement.     

Enantioselective Sulfoxidation Catalyzed by a Bisguanidinium Diphosphatobisperoxotungstate Ion Pair

The first enantioselective tungstate‐catalyzed oxidation reaction is presented. High enantioselectivities were achieved for a variety of drug‐like phenyl and heterocyclic sulfides under mild conditions with H₂O₂, a cheap and environmentally friendly oxidant. Synthetic utility was demonstrated through the preparation of (S)‐Lansoprazole, a commercial proton‐pump inhibitor. The active ion‐pair catalyst was identified to be bisguanidinium diphosphatobisperoxotungstate using Raman spectroscopy and computational studies.     

A Biodegradable Polydopamine‐Derived Electrode Material for High‐Capacity and Long‐Life Lithium‐Ion and Sodium‐Ion Batteries

Polydopamine (PDA), which is biodegradable and is derived from naturally occurring products, can be employed as an electrode material, wherein controllable partial oxidization plays a key role in balancing the proportion of redox‐active carbonyl groups and the structural stability and conductivity. Unexpectedly, the optimized PDA derivative endows lithium‐ion batteries (LIBs) or sodium‐ion batteries (SIBs) with superior electrochemical performances, including high capacities (1818 mAh g^?1 for LIBs and 500 mAh g^?1 for SIBs) and good stable cyclabilities (93 % capacity retention after 580 cycles for LIBs; 100 % capacity retention after 1024 cycles for SIBs), which are much better than those of their counterparts with conventional binders.