Effects of Self—coiling of Organic Molecules on Intramolecular Exciplex Formation and Fluoresscence Quenching in DX—H2O Solvent System

Effects of self-coiling of organic molecules on intramolecular exciplex formation of compound I,in which the carbazole chromophore and terephthalic acid methylester acceptor group are linked by one (CH2)10 chain,and the decrease of the fluorescence intensities of compounds Ⅱ，Ⅲ，and Ⅳ,in which the carbazole chromophore and 3,5-dinitrobenzoate are connected by one aliphatic chain of (CH2)10 (Ⅱ），（CH2）12（Ⅲ）,or (CH2)4(Ⅳ）,have been studied in the dioxane (DX)-H2O binary system.The results show that self-coiling of organic molecules in DX-H2O facilitates intramolecular exciplex formation of I and induces the decrease of fluorescence intensities of Ⅱ,bacause of the proximity effect brought about by selfcoiling of organic molecules under hydrophobic-lipophilic interaction(HLI) between the excited carbazole chromophore and the acceptor.Since the similar effects are observed even when the concentration of the probes are less than their CAgCs(critical aggregate concentrations )in the DX-H2O mixture with the same φ values,formation of the intermolecular exciplex has been excluded.The effects are found to be strongly depended on φ values,indication that they are mainly driven by HLI.The properties of the acceptors can also affect the intramolecular exciplex formation.With terephthalic acid methylester moiety as the acceptor,the carbazole chromophore exhibits the fluorescence spectra of the exciplex,while with 3,5-dinitrobenzoate moiety as the acceptor,only the fluorescence spectra of excited carbazolyl chromophore are observed.     

Sesquiterpenoids and Phenylpropane Derivatives from Sonchus uliginosus

Six new compounds were isolated from the whole plant of Sonchus uliginosus, including three eudesmane‐type sesquiterpenoids (1β,6α)‐1,6,14‐trihydroxyeudesm‐3‐en‐12‐oic acid γ‐lactone ( 1 ), (1β,6α)‐1,6,14‐trihydroxyeudesma‐3,11(13)‐dien‐12‐oic acid γ‐lactone ( 2 ), and (1β,6α)‐1,6‐dihydroxy‐14‐O‐[(4‐hydroxyphenyl)acetyl]eudesma‐3,11(13)‐dien‐12‐oic acid γ‐lactone ( 3 ), and three phenylpropane derivatives, 4‐hydroxy‐γ,3,5‐trimethoxybenzenepropanol ( 6 ), γ,3,4,5‐tetramethoxybenzenepropanol ( 7 ), and γ,3,4,5‐tetramethoxybenzenepropanol acetate ( 8 ), together with the two known compounds 4 and 5 . The new structures were elucidated by means of spectroscopic methods, such as IR, EI‐MS, HR‐ESI‐MS, 1D‐ and 2D‐NMR, and by comparison of the spectroscopic data with those reported for structurally related compounds.     

Ni基六铝酸镧LaNiAl11O19催化剂表面甲烷CO2的重整积炭速率

甲烷二氧化碳重整制合成气反应过程中,催化剂表面积炭是制约催化反应顺利进行的关键因素。研究催化剂表面积炭物种及积炭速率,找出影响催化剂表面积炭的动力学因素,对建立合理的催化重整反应体系,完善催化剂表面积炭的动力学理论具有重要的理论和实际意义。目前有关催化剂表面积炭速率的研究报道较少[1,2]。Ｎｉ基六铝酸盐催化剂对甲烷二氧化碳重整制合成气具有很好的催化活性和稳定性[3,4]。本文利用Ｘ 射线光电子能谱(ＸＰＳ)和热重分析(ＴＧＡ)技术,在还原态Ｎｉ基六铝酸镧ＬａＮｉＡｌ11Ｏ19催化剂表面研究了甲烷裂解积炭和甲烷二氧…     

Time-dependent density functional theory calculations of the photoabsorption of fluorinated alkanes

Time-dependent density functional theory (TD-DFT) calculations of the transition energies and oscillator strengths of fluorinated alkanes have been performed. The TD-DFT method with the non-local B3LYP potential yields transition energies for the methanes, which are smaller by about 10% as compared to the experimental values. An empirical linear correlation was found between the calculated and experimental transition energies both at the B3LYP/DZ+Ryd(C, F) and B3LYP/cc-pVTZ+Ryd(C, F, H) levels for a total of 19 transitions of the fluorinated methanes with linear correlation coefficients of 0.987 for the former and 0.988 for the latter. This empirical correlation for fluorinated methane molecules is found to agree well with the previously obtained empirical correlations between calculated and experimental values for non-fluorinated molecules. The results show that a single empirical-correlation relationship can be used for both non-fluorinated and fluorinated molecules to predict transition energies. This linear relationship is then used to predict the photoabsorption spectra of ethane, propane, butane, and partially and fully fluorinated derivatives. A key result of these calculations is the dominance of Rydberg transitions in the spectral region of interest.     

Highly Regioselective Sequential 1,1‐Dihydrosilylation of Terminal Aliphatic Alkynes with Primary Silanes

A regioselective double 1,1‐hydrosilylation of terminal aliphatic alkynes with primary silanes catalyzed by one cobalt catalyst has been developed. gem‐Bis(dihydrosilyl)alkanes containing four silicon‐hydrogen bonds are efficiently constructed in an atom‐economical manner. Tolerated substrates include simplest alkyne‐ethyne, a complicated drug derivative and various functionalized terminal aliphatic alkynes. Asymmetric approach using two catalysts is achieved with excellent enantioselectivities to access corresponding chiral products. The transformations of Si—H bonds into Si—C, Si—O, and Si—F bonds and the synthesis of enantioriched α‐hydroxysilane show synthetic utility.     

Theoretical determination of chromophores in the chromogenic effects of aromatic neurotoxicants

We report the first computational study of the chromophores responsible for the chromogenic effects of aromatic neurotoxicants containing a 1,2-diacetyl moiety in their oxidation metabolites. A series of ab initio electronic structure calculations was performed on two representative aromatic compounds, 1,2-diacetylbenzene (1,2-DAB) and 1,2-diacetyl tetramethyl tetralin (1,2-DATT), the putative active metabolites of the neurotoxic aromatic hydrocarbon compounds 1,2-diethylbenzene (1,2-DEB) and acetyl ethyl tetramethyl tetralin (AETT), and on the products of their possible reactions with proteins that result in chromogenic effects. The electronic excitation energies determined by three different computational approaches were found to be consistent with each other. The calculated results are consistent with the conclusion/prediction that the chromogenic effects of 1,2-DAB (or 1,2-DEB) and 1,2-DATT (or AETT) could result from ninhydrin-like reactions, rather than the formation of pyrrole-like compounds. Our pK(a) calculations further indicate that the chromophore, i.e., the product of the ninhydrin-like reaction showing the blue color, is deprotonated in neutral aqueous solution. The corresponding protonated structure has a different color as it absorbs in the blue region of the visible spectrum, and its chromogenic contribution would be significant in solution at low pH.     

Asynchronous multicanonical basin hopping method and its application to cobalt nanoclusters

The multicanonical basin hopping (MUBH) method, which uses a multicanonical weight in the basin hopping (BH) Monte Carlo method, was found to be very efficient for global optimization of large-scale systems such as Lennard-Jones clusters containing more than 150 atoms. We have implemented an asynchronous parallel version of the MUBH method using the message passing interface (MPI) to take advantage of the full usage of multiprocessors in either a homogeneous or heterogeneous computational environment. Based on the intrinsic properties of the Monte Carlo method, this MPI implementation used the task parallelism to minimize interthread data communication. For a Co nanocluster consisting of N atoms, we have applied the asynchronous multicanonical basin hopping (AMUBH) method (for 181 < N < or = 200), together with BH (for 2 < or = N < 150) and MUBH (for 150 < or = N < or = 180), to search for the molecular configuration of the global energy minimum. AMUBH becomes the only practical computational scheme for locating the energy minimum within realistic computational time for a relatively large cluster.     

硝基苯加氢合成对氨基酚用负载铂催化剂的制备

 用甲醛还原沉积法制备了活性炭负载的铂催化剂（Pt／AC）和不\r\n同载体负载的铂催化剂，并考察了催化剂对硝基苯加氢制备对氨基酚反\r\n应的催化性能．结果表明，还原Pt（Ⅳ）的甲醛用量是影响催化剂性能\r\n的关键因素，甲醛必须过量而且存在一个最佳值．增加催化剂的铂负载\r\n量，不能有效提高加氢反应速度，反而易降低对氨基酚选择性；低铂负\r\n载量催化剂具有较高的活性、选择性及稳定性．XPS和TEM表征结果表明\r\n，金属铂集中分布于活性炭颗粒外部，其颗粒大小介于2～12nm间．炭\r\n载体催化剂的活性和选择性明显高于金属氧化物载体催化剂．掺入适量\r\n的Mg可显著提高Pt／AC催化剂的活性和选择性．     

Quassinoids from seeds of Brucea Javanica and their anticomplement activities

Abstract

An investigation on seeds of Brucea javanica led to the acquisition of a new quassinoid, 20-hydroxyyadanzigan (1), along with five known quassinoids (2–6). The structure of the new compound was elucidated on the basis of extensive spectral analysis. All of the compounds were assayed for their anticomplement activities through classical and alternative pathways. Compounds 1–6 exhibited potent anticomplement activity with CH₅₀ and AP₅₀ values of 0.032–0.075?mg/mL and 0.061–0.118?mg/mL, respectively. Moreover, the structure-activity relationships of these compounds are discussed.

     

Simultaneous Determination of Aromatic Amines by Liquid Chromatography Coupled with Carbon Nanotubes/Poly (3-methylthiophene) Modified Dual-Electrode

Liquid chromatography with amperometric detection (LC-AD) is developed and applied to simultaneously determine five aromatic amines. In the LC-AD, a new carbon nanotubes/poly(3-methylthiophene) modified dual-electrode is fabricated and then used as the working electrode. It is found that this chemically modified electrode (CME) exhibits efficiently electrocatalytic oxidation for aromatic amines with relatively high sensitivity, stability and long-life. Thus, lower detection in LC-AD can be achieved, which are 4.0 × 10^–8 mol L^–1 for aniline, 1.6 ×10^–7 mol L^–1 for 4-nitroaniline, 1.0 × 10^–7 mol L^–1 for 4-chloroaniline, 1.5 × 10^–7 mol L^–1 for 1-naphthylamine, 1.7 × 10^–7 mol L^–1 for 2-bromoaniline. The recoveries of the five analytes are also determined, which range between 0.95 and 1.05 for drinking water, 0.86 and 1.10 for the LiWa River water.