Synthesis of a carbosilane dendrimer with the functional inner shell

The carbosilane dendrimer of the fifth generation with the functional inner and nonfunctional outer shells in the molecular structure was synthesized for the first time. The efficiency of the hybrid scheme of carbosilane dendrimer synthesis based on the use of organomagnesium and organolithium reagents at different steps of molecular structure formation and hydrosilylation was shown.     

Hydrogenation of aldehydes and ketones catalyzed by a polysulfosiloxane–platinum complex

An acidic inorganic polymer, polysulfosiloxane, has been prepared and used as ligand for preparing a polysulfosiloxane–platinum complex. It has been found that such a complex could catalyze the hydrogenation of aldehydes and ketones to alcohols, giving as much as 100% yield at room temperature and under atmospheric pressure. Temperature, S/Pt molar ratio in the complex and solvents greatly influenced the reaction. This complex was very stable and could be used several times without any change in catalytic activity.     

Hydrogenation of m-xylene catalyzed by a silica-supported polysilazane–platinum complex

A new kind of inorganic polymer, silica-supported polysilazane (Si–N), and its platinum complex (Si–N–Pt) were prepared and characterized by X-ray photoelectron spectroscopy. It was found that Si–N–Pt can catalyze hydrogenation of m-xylene under mild conditions (30–50°C, 1 atm). The products of the reaction were cis- and trans-1,3-dimethylcyclohexane. The formation of trans-1,3-dimethylcyclohexane may be adequately explained according to the “roll-over” model. The stereoselectivity was influenced by temperature and catalyst concentration, the proportion of the cis isomer decreasing with an increase in each of the two factors. The effects of other reaction parameters, such as the N/Pt mole ratio in the complex, solvents and reaction time, etc., on the hydrogenation of m-xylene were also studied. The Si–N–Pt catalyst is very stable in reaction and turnover numbers amount to 520 in 70 hr.     

Hydrogenation of norbornene catalyzed by magnesium oxide-supported polyalumazane–platinum complexes

A magnesium oxide-supported polyalumazane–platinum complex was synthesized and characterized by X-ray photoelectron spectroscopy (XPS) and its performance toward the hydrogenation of norbornene. XPS data indicated that a large amount of platinum existed in a zero-valent state. The catalyst showed high performance for the hydrogenation of norbornene. Its performance depended on the type of the support, the platinum loading and the reaction temperature. With 0.1544 mmol/g platinum loading at 25°C, the hydrogenation of norbornene to norbornane was completed within 2 min. Also, the turnover number of the catalyst reached 11,000 within 280 min.     

High Selective Hydrogenation of Acetophenone Catalyzed by Alumina Supported platinum Nanoclusters

A new preparation and reduction method of γ-Al2O3 supported and PVP stabilized platinuzn nanoclusters was studied.The catalyst exhibited very high very high activity and selectivity for acetophenone hydrogenation in isopropanol-KOH solution at 25-60℃ and PH2=1-5 MPa.     

Hydrogenation of phenylpyruvic acid to phenylalanine catalyzed by Ni-B/SiO2

Phenylalanine （Phe） is a significant amino acid that cannot be synthesized by human themselves but must be taken from environment. It was initially found that the nanosized amorphous Ni-B/SiO2 alloy prepared by the chemical reduction method was an effective catalyst for the preparation of Phe from phenylpyruvic acid （PPA） by amination and hydrogenation. It has been found that the amorphous Ni-B/SiO2 alloy catalyst exhibits superior activity and selectivity to the traditional catalysts Raney Ni and Urushibara nickel. The effects of reaction time, amounts of catalysts and ammonia solution, reaction temperature, and H2 pressure on the reaction have been investigated systematically. The results indicated that the yield of Phe was 97.9%, and the selectivity for Phe reached 98.9% when the reaction was carried out for 3 h at 333 K and 2.0 MPa of H2 with m（Cat.） ： m（PPA） = 0.6 ： 1.0 and n（NH3） ： n（PPA） = 3 ： 1. The catalysts were characterized by XRD, AAS, XPS, BET, and TEM, and the relationship between the catalyst structure and the catalytic activity was discussed in detail. It was found that the reason why Ni-B/SiO2 amorphous alloy catalyst was much more active for the preparation of Phe could be accounted for by the presence of electron-rich Ni due to electron donation from alloying B; the smaller size of Ni-B particles, the larger specific surface area of Ni-B/SiO2.     

Ruthenium/dendrimer complex immobilized on silica-functionalized magnetite nanoparticles catalyzed oxidation of stilbenes to benzil derivatives at room temperature

A new ruthenium/dendrimer complex stabilized on the surface of silica-functionalized nano-magnetite was fabricated and well characterized. The nano-catalyst showed good activity in the synthesis of benzil derivatives via the oxidation of stilbenes with high turnover frequency (TOF) at room temperature. Moreover, the catalyst could also be reused up to fifteen times without any loss of its activity.     

Glucose biosensor based on immobilization of glucose oxidase in platinum nanoparticles/graphene/chitosan nanocomposite film

The bionanocomposite film consisting of glucose oxidase/Pt/functional graphene sheets/chitosan (GOD/Pt/FGS/chitosan) for glucose sensing is described. With the electrocatalytic synergy of FGS and Pt nanoparticles to hydrogen peroxide, a sensitive biosensor with a detection limit of 0.6 μM glucose was achieved. The biosensor also has good reproducibility, long-term stability and negligible interfering signals from ascorbic acid and uric acid comparing with the response to glucose. The large surface area and good electrical conductivity of graphene suggests that graphene is a potential candidate as a sensor material. The hybrid nanocomposite glucose sensor provides new opportunity for clinical diagnosis and point-of-care applications.     

常压下由对甲酚催化氢化制备4—甲基环己酮

4-甲基环己酮作为一种优良的有机溶剂及有机合成中间体,在微电子工业及医药、香料、精细化工合成中有很重要的用途。文献报道的各种制备方法中,以对甲酚为原料经催化氢化制备4-甲基环己酮有实际意义。但催化氢化大多在加压情况下进行,所用催化剂多为钯,也有用钉、铑或莱尼镍作催化剂的,但加氢产物多为甲基环己醇,且酮的收率很低。本文采用铑催化剂(以氧化铝作载体),实现了对甲酚的常压催化氢化,制得4-甲基环己酮,并对催化条件作了初步摸索和探讨。     

Electrochemical determination of quercetin by self-assembled platinum nanoparticles/poly(hydroxymethylated-3,4-ethylenedioxylthiophene) nanocomposite modified glassy carbon electrode

A simple and sensitive platinum nanoparticles/poly(hydroxymethylated-3,4-ethylenedioxylthiophene)nanocomposite(PtNPs/PEDOT-MeOH) modified glassy carbon electrode(GCE) was successfully developed for the electrochemical determination of quercetin.Scanning electron microscopy and energy dispersive X-ray spectroscopy results indicated that the PtNPs were inserted into the PEDOTMeOH layer.Compared with the bare GCE and poly(3,4-ethylenedioxythiophene)(PEDOT) electrodes,the PtNPs/PEDOT-MeOH/GCE modified electrode exhibited a higher electrocatalytic ability toward the oxidation of quercetin due to the synergic effects of the electrocatalytic activity and strong adsorption ability of PtNPs together with the good water solubility and high conductivity of PEDOT-MeOH.The electrochemical sensor can be applied to the quantification of quercetin with a linear range covering0.04-91 μmol L~(-1) and a low detection limit of 5.2 nmol L~(-1).Furthermore,the modified electrode also exhibited good reproducibility and long-term stability,as well as high selectivity.     

钌分子氢配合物催化烯烃的离子氢化

在氢气压力下，钌配合物[^MeCnRuCl(dppe)](O3SCF3)与AgO3SC3在CH2Cl2中反应生成分子氢配合物[^MeCnRu(H2)(dppe)](O3SCF3)2，该分子氢配合物具有催化烯烃离子氢化的活性。原位高压核磁共振研究显示，这种催化离子氢化反应可能是由分子氢配合物向烯烃转移氢质子形成碳正离子引起的。     

Synthesis and characterization of platinum monolayer oxygen-reduction electrocatalysts with Co–Pd core–shell nanoparticle supports

We synthesized Pt monolayer electrocatalysts for oxygen-reduction using a new method to obtain the supporting core–shell nanoparticles. They consist of a Pt monolayer deposited on carbon-supported Co–Pd core–shell nanoparticles with the diameter of 3–4 nm. The nanoparticles were made using a redox-transmetalation (electroless deposition) method involving the oxidation of Co by Pd cations, yielding a Pd shell around the Co core. The quality of the thus-formed core–shell structure was verified using transmission electron microscopy and X-ray absorption spectroscopy, while cyclic voltammetry was employed to confirm the lack of Co oxidation (dissolution). A Pt monolayer was deposited on the Co–Pd core–shell nanoparticles by the galvanic displacement of a Cu monolayer obtained by underpotential deposition. The total noble metal mass-specific activity of this Pt monolayer electrocatalyst was ca. 3-fold higher than that of commercial Pt/C electrocatalysts.     

Hydrogenation of sorbic acid in mono- and biphasic systems catalyzed by Rh(I)- phosphine complexes

Hydrogenation of sorbic acid in ethyl acetate with [RhCl(PPh₃)₃] was studied and compared to the hydrogenation of its K-salt in water catalyzed by [RhCl(mtppms)₃]. Aqueous biphasic hydrogenation of sorbic acid with [RhCl(mtppms)₃] as catalyst proceeded faster and more selectively than that in homogeneous solutions and afforded trans-hex-2-enoic acid with 80% selectivity.     

辛可尼定修饰的铂纳米簇合物催化丙酮酸甲酯不对称加氢反应的研究

研究了辛可尼定(cinchonidine)作手性修饰剂修饰的氧化铝负载铂纳米簇合物(Pt-PVP-γ-Al2O3)催化丙酮酸甲酯不对称氢化反应,采用甲醇的碱溶液做溶剂,着重考察了低温条件下催化剂的活性和对映选择性的变化.优化的反应条件为0℃,5.0MPaH2,[cinchonidine]=3.24×10-3mol/L,[KOH]=0.02mol/L,1h内丙酮酸甲酯不对称加氢的转化率为32.2%,对映选择性达到52.2%;     

4-硝基二苯胺和4-亚硝基二苯胺钠催化加氢制4-氨基二苯胺 Ⅰ.溶剂对加氢反应的影响

用Pd—M/C催化剂(M为非贵金属),对工业原料4-硝基二苯胺及4-亚硝基二苯胺钠催化加氢制4-氨基二苯胺,其活性和选择性都较好。本文报导了在常压加氢中添加各种溶剂对反应的影响,并建议采用苯胺溶剂较适宜。     

水溶性含钌-铂双金属催化剂催化卤代芳香硝基化合物选择性加氢

考察了水溶性Ru/Pt-TPPTS双金属催化剂催化卤代芳香硝基化合物的加氢性能.实验结果表明,在Ru-TPPTS中添加铂或钯后,反应活性明显提高,尤其是Ru/Pt-TPPTS双金属催化剂更表现出显著的双金属协同效应.在pH₂=1.0MPa,70℃,反应2h的条件下,双金属催化剂0.50Ru/0.50Pt-TPPTS催化对-氯硝基苯加氢生成对-氯苯胺的反应转化率达到100%.对于取代基和取代位置不同的一些卤代硝基苯加氢,该双金属催化剂也表现出很高的催化活性和生成卤代苯胺的选择性,脱卤反应的程度很小.     

Synthesis of Pt/ionic liquid/graphene nanocomposite and its simultaneous determination of ascorbic acid and dopamine

A water-soluble and electroactive composite - Pt nanoparticles/polyelectrolyte-functionalized ionic liquid (PFIL)/graphene sheets (GS) nanocomposite was synthesized in one pot. The structure and composition of the Pt/PFIL/GS nanocomposite were studied by means of ultraviolet-visible (UV-vis) and X-ray photoelectron spectra (XPS). Scanning electron microscopy (SEM) and transmission electron microscope (TEM) images reveal Pt nanoparticles are densely dispersed on the transparent thin PFIL-functionalized graphene sheets. The obtained Pt/PFIL/GS nanocomposite-modified electrode was fabricated to simultaneously determine ascorbic acid (AA) and dopamine (DA) by cyclic voltammetry. It is worthwhile noting that the difference between the two peak potentials of AA and DA oxidation is over 200 mV, which leads to distinguishing AA from DA. The detection of increasing concentrations of AA in the presence of DA and the oxidation of continuous addition of DA in the presence of AA were also studied using differential pulse voltammetry. The proposed sensor in real sample analysis was also examined in human urine samples. Three independent oxidation peaks appear in urine sample containing AA and DA. Therefore, the Pt/PFIL/GS nanocomposite might offer a good possibility for applying it to routine analysis of AA and DA in clinical use.     

Hydrogenation of aldehydes catalyzed by kieselguhr‐supported carboxymethylcellulose‐nickel complex

A new kieselguhr‐supported carboxymethylcellulose‐nickel complex (Kie‐CMC‐Ni) has been prepared by a simple method, which has been found to catalyze the hydrogenation of benzaldehyde, valeraldehyde and isobutyraldehyde to the corresponding alcohols in high yield (100, 92 and 86% respectively). The catalyst could be reused without obvious loss of its catalytic activity. Copyright © 2004 John Wiley & Sons, Ltd.     

Deposition of gallium oxide nanodots prepared from metal‐assembling dendrimer molecules isolated by the spacing of the nonmetal‐assembling dendrimer molecules in the two‐dendrimers mixture monolayer

Phenylazomethine dendrimers (DPA) can precisely incorporate metal chlorides onto the imine sites in a stepwise fashion. Such precise dendrimer–metal complexes allow the preparation of size‐controlled subnanometer metal particles. We now propose a novel approach for the fabrication of size‐controlled subnanometer metal oxide dots isolated on a substrate using two different‐type dendrimers. One is a fourth‐generation phenylazomethine dendrimer (DPAG4) and the other is a benzylether dendrimer (BzEG3) with a zinc porphyrin core. Even though the diameter of BzEG3 corresponds to that of DPAG4, BzEG3 has no metal‐complexing site. Upon dip coating on a highly oriented pyrolytic graphite substrate by the mixed solution of the metal chloride‐assembling DPAG4 molecules and BzEG3 molecules, the dendrimer monolayer was immobilized on the substrate. The concentration of the dendrimer mixture was determined in order to separate each DPAG4–metal chloride complex molecule by BzEG3. Monodispersed metaloxide nanodot arrays could be obtained from the dendrimer monolayer in which DPAG4–metal chloride complex molecule is well isolated by the BzEG3 as a spacer after the hydrolysis of metal chlorides followed by the complete removal of dendrimers. Copyright © 2013 John Wiley & Sons, Ltd.     

Catalytic Hydrogenation of Halosteroidal Derivatives by Bipyridine or Phenanthroline Complexes of Copper(II) in Hydrazine Aqueous Media

We report two synthetic systems, Cu(Bpy)²⁺ and Cu(Phen)²⁺, for catalytic hydrogenation of steroidal haloalkenes in the presence of hydrazine and air. Thesestudies demonstrated that the selective hydrogenation is faster for the 1,10‐phenanthroline–Cu(II) system because forming more stable copper complex are formed, leaving fewer free copper ions in solution. Evidence also supports that the catalytic power of Cu(II) ions can be tuned moderately through the addition of bidentate ligand, Bpy or Phen.