An efficient approach towards the convergent synthesis of "fully-carbohydrate" mannodendrimers

Glycosylation of sugar trityl ethers with sugar 1,2-O-(1-cyano)ethylidene derivatives (the trityl-cyanoethylidene condensation) has been applied to the synthesis of highly branched (dendritic) mannooligosaccharides incorporating a Manalpha1-->3(Manalpha1-->6)Man structural motif. The convergent synthetic strategy used to assemble these oligosaccharides was based on the use of glycosyl acceptors and/or a glycosyl donor already bearing this structural motif. The former were represented by mono- and ditrityl ethers of ManalphaOMe, Manalpha1-->3ManalphaOMe, and Manalpha1-->3(Manalpha1-->6)ManalphaX, where X=OMe or SEt. The pivotal glycosyl donor was the peracetylated 1,2-O-(1-cyano)ethylidene-3,6-di-O-(alpha-D-mannopyranosyl)-beta-D-mannopyranose (1), prepared by orthogonal Helferich glycosylation of the known 1,2-O-(1-cyano)ethylidene-beta-D-mannopyranose with tetra-O-acetyl-alpha-D-mannopyranosyl bromide followed by O-acetylation. Glycosylation of acetates of methyl 6-O-trityl-alpha-D-mannopyranoside and methyl 3,6-di-O-trityl-alpha-D-mannopyranoside with one equivalent of the donor 1 gave rise to the isomeric tetrasaccharide derivatives, Manalpha1-->3(Manalpha1-->6)Manalpha1-->6ManalphaOMe and Manalpha1-->3(Manalpha1-->6)Manalpha1-->3ManalphaOMe, respectively. The latter derivative was further mannosylated at the remaining 6-O-trityl acceptor site to give the protected pentasaccharide Manalpha1-->3(Manalpha1-->6)Manalpha1-->3(Manalpha1-->6)ManalphaOMe. The isomeric pentasaccharide, Manalpha1-->3(Manalpha1-->6)Manalpha1-->6(Manalpha1-->3)ManalphaOMe, was prepared by reaction of 1 with the 6-O-trityl derivative of (Manalpha1-->3)ManalphaOMe. In a similar fashion, 6'- and 6"-O-trityl derivatives of the branched trisaccharide Manalpha1-->3(Manalpha1-->6)ManalphaOMe served as precursors for two isomeric mannohexaosides. The 3,6-di-O-trityl ether of ManalphaOMe and the 6',6"-di-O-trityl ether of Manalpha1-->3(Manalpha1-->6)ManalphaX (X=OMe or SEt) were efficiently bis-glycosylated with the donor 1 to give the corresponding protected mannoheptaoside and mannononaoside. The yields of these glycosylations with the donor 1 ranged from 50 to 66 %. Final deprotection of all the oligosaccharides was straightforward and afforded the target products in high yields. Both the acylated and deprotected products were characterized, and the intersaccharide connectivities were elucidated by extensive one- and two-dimensional NMR spectroscopy. The described blockwise convergent approach allows assembly of a variety of 3,6-branched mannooligosaccharides.     

Synthesis and Structure of Triphenylantimony Bis(Acetophenoneoximate)

Triphenylantimony bis(acetophenoneoximate) was synthesized by the reaction of triphenylantimony with hydrogen peroxide in the presence of acetophenone oxime (taken in the molar ratio of 1 : 1 : 2) in ether. The structure of the obtained compound was determined by X-ray diffraction. The Sb atom has a distorted trigonal-bipyramidal coordination with the oxime groups in the axial positions. The Sb–C(Ph)_eq bond lengths are 2.110(1)–2.113(1) Å, and the Sb–O distances are 2.058(1) and 2.067(1) Å. The intramolecular Sb(1)···N(1, 2) contacts and O(1)SbO(2) axial angle are 2.990(1), 2.916(1) Å and 172.49(4)°, respectively.     

Isolation,Structural Elucidation,Antioxidant and Hypoglycemic Activity of Polysaccharides of Brassica rapa L.

The aim of this study was to investigate the effects of microwave ultrasonic-assisted extraction (MUAE) on the content, structure, and biological functions of Brassica rapa L. polysaccharide (BRP). Response surface methodology (RSM) was used to optimize the parameters of MUAE, and it obtained a polysaccharide with yield of 21.802%. Then, a neutral polysaccharide named BRP-1-1 with a molecular weight of 31.378 kDa was isolated and purified from BRP using DEAE-650 M and Sephadex G-100. The structures of the BRP-1-1 were elucidated through a combination of FT-IR, GC-MS, NMR, and methylation analysis. The results showed that BRP-1 consisted of mannose (Man) and glucose (Glu) in a molar ratio of 7.62:1. The backbone of BRP-1-1 mainly consisted of →6)-α-D-Glup-(1→4-β-D-Glup-(1→2)-α-D-Manp-(1→2)-α-D-Glup-(1→, the branch was [T-α-D-Manp-(1]_n→. BRP-1-1 intervention significantly inhibited α-glucosidase activity; an inhibition rate of 44.623% was achieved at a concentration of 0.5 mg/mL. The results of the in vitro biological activity showed that BRP-1-1 has good antioxidant and hypoglycemic activity, suggesting that BRP-1-1 could be developed as a functional medicine.     

Pt 含量对Co@Pt/C核壳结构催化剂性能的影响

采用两步还原法制得Co@Pt/C核壳结构催化剂, 其中Co与Pt 的总质量分数为20%. 通过改变金属前驱体的用量, 制备了不同Co:Pt 原子比的Co@Pt/C 催化剂, 以20% (w) Co@Pt(1:1)/C 与20% (w) Co@Pt(1:3)/C 表示. 采用透射电镜(TEM)、光电子射线能谱分析(XPS)、循环伏安(CV)、线性扫描伏安(LSV)等方法考察了其结构与性能, 并与实验室早先制备的40% (w) Co@Pt/C 催化剂进行了比较. 自制20% Co@Pt(1:1)/C 与20% Co@Pt(1:3)/C 催化剂的金属颗粒直径约为2.2-2.3 nm, 在碳载体上分散均匀, 粒径分布范围较窄, 电化学活性比表面积(ECSA)分别为56 和60 m²·g^-1, 均超过商用催化剂20% Pt/C(E-tek) (ECSA=54 m²·g^-1). 20%Co@Pt(1:1)/C 与20% Co@Pt(1:3)/C 的半波电位相较于40% Co@Pt(1:1)/C 和40% Co@Pt(1:3)/C 均向正向移动, 表现出更好的氧还原(ORR)催化活性, 并有望降低催化剂的成本, 在质子交换膜燃料电池领域表现出良好的应用前景.     

Supramolecular and metallosupramolecular coordination compounds of nickel(II) with the half units of vicinal oxime–imine ligands; mixed ligand complexes of the metal ion

The [1+1] condensation of isonitrosoacetylacetone (Hisoacac) with o-phenylenediamine produces the diazepine (HLBD) (1), which reacts with Ni(OAc)₂· 4H₂O (1:1 molar ratio) to produce the mixed ligand complex (LBDN)Ni(OAc) (2); where LBDN is the anion of the half unit obtained by hydrolysis of one HLBD imine linkage. The reaction of (2) (1 mol) with mono-, bi- and trichloroethanoic acid (1mol) or picric acid (1mol) led to the exchange of the acetate in (2) with the anion of the added acid [(3)–(6), respectively]. The supramolecular structure of (2)–(6) is achieved through the dimerization of these complexes via intermolecular hydrogen bonding of the LBDN –NH₂ group of one molecule and the monodentate acetate group of another molecule. The template reaction of o-phen with Hisoacac in the presence of Ni(OAc)₂·4H₂O (1:2:2 and 1:2:1 molar ratios, respectively) led to the formation of (LBDN)Ni(OAc)₂Ni(isoacac) (7) and (isophen)Ni (8), respectively; H₂isophen is a symmetrical Schiff base ligand formed by the (2:1) in situ condensation of Hisoacac with o-phen. The (1:1) condensation of Hisoacac with p-phen produced the half unit Hisopphen (9), whose 1:1 molar ratio reaction with Ni(OAc)₂·4H₂O led to the formation of (isopphen)Ni(OAc)·2H₂O (10). The amino group of the isopphen ligand is available for further coordination with the nickel(II) ion to produce the metallosupramolecular complexes {[two molecules of complex (10)] [Ni(OAc)₂]} and {[complex (10)] [Ni(OAc)₂·H₂O]} from the 2:1 and 1:1 molar ratio reactions, respectively, of (10) with Ni(OAc)₂·4H2O. The 1:1 molar ratio reaction of (10) with Hisoacac led to replacement of OAc by isoacac. The suggested structures of the ligands and their coordination compounds are based on analytical, chemical, spectral data and magnetic moments.     

Nano level detection of Cd(II) using poly(vinyl chloride) based membranes of Schiff bases

The construction and performance characteristics of polymeric membrane electrodes based on two neutral ionophores, 2,2′-(1Z,1′Z)-(1E,1′E)-(1,2-phenylenebis(methan-1-yl-1-ylidene))bis(azaan-1-yl-1-ylidene)bis(methylene)bis(azan-1-yl-1-ylidene)bis(methan-1-yl-ylidene)diphenol (L₁) and 4,4′-(1E,1′E)-(butane-1,4-diylbis(azan-1-yl-1-ylidene))bis(methan-1-yl-1-ylidene)dinaphthalen-1-ol (L₂) for quantification of cadmium ions, are described. The influences of membrane compositions on the potentiometric response of the electrodes have been found to substantially improve the performance characteristics. The best performance was obtained with the electrode having a membrane composition (w/w) of (L₁) (2.6%):PVC (31.6%):DOP (63.2%):NaTPB (2.6%). The proposed electrode exhibits Nernstian response in the concentration range 5.0 × 10⁻⁹ to 1.0 × 10⁻¹ M Cd²⁺ with limit of detection 3.1 × 10⁻⁹, performs satisfactorily over wide pH range (2.0-8.5) with a fast response time (11 s). The electrode has been found to work satisfactorily in partially non-aqueous media up to 40% (v/v) content of methanol, ethanol and acetonitrile and could be used for a period of 2.5 months. The analytical usefulness of the proposed electrode has been evaluated by its application in the determination of cadmium in cigarette samples. The practical utility of the membrane electrode has also been observed in the presence of surfactants.     

Si(1 1 1)-(6 × 6)Au surface morphology and nucleation of Pb at low temperature

The morphologies of the Si(1 1 1)-(6 × 6)Au surface and the nucleation of Pb have been investigated at temperatures below room temperature using scanning tunnelling microscopy (STM). The STM scans of the clean Si(1 1 1)-(6 × 6)Au surface revealed exceptionally rich and strongly bias-dependent details within the unit cell. After deposition of about 0.01 ML of Pb(1 1 1), at temperatures above 180 K, the single Pb atoms formed a two-dimensional mesh with (6 × 6)-Au periodicity. In this early stage of deposition, the Pb atoms occupied predominantly one specific site of the (6 × 6) unit cell. The local symmetry of this site determined the further growth of the Pb layer. As a consequence, the structure of the Pb layer on Si(1 1 1)-(6 × 6)Au is rotated of 30° relative to that of the Pb layer on Si(1 1 1)-(7 × 7).     

The photochemical reaction of (E,E)-dibenzylidenesuccinic thioanhydride: A spectroscopic and structural study

The first photochromic thioanhydride, (E,E)-2,3-dibenzylidenesuccinic thioanhydride ( 1b ), was synthesized. Irradiation of ( 1b ) in benzene, dichloromethane, or chloroform gives isomerization and cyclization products similar to those obtained for the anhydride analogue ( 1a ). The crystal structure of ( 1b ) was determined (X-rays) and compared to the structures of the anhydridge ( 1a ) and N-phenylimide ( 1c ). ¹H and ¹³C NMR spectra were recorded, and the electron charge densities of the carbon atoms were calculated with AM1. These results are discussed and compared with those for the compounds 1a–1c . The thioanhydride ( 1b ) ring is much more twisted than either the anhydridge ( 1a ) or the imide ( 1c ) rings. The linear relationship between the ¹³C NMR chemical shifts and the electron charge density on the given atom has been investigated. The C(carbonyl) and C(α) carbon atoms of 1b were found to be greatly deshielded relative to the corresponding atoms in 1a and 1b . The increase in corresponding atoms in 1a and 1b . The increase in sensitivity toward cyclization of the thioanhydridge ( 1b ) is attributed to the marked change in the charge distribution. Crystal data. Thioanhydride ( 1b ): space group P2_1/c with a = 12.956(3) Å, b = 14.843(6) Å, c = 7.512(6) Å, β = 98.05(2)°, Rw = 0.085 and R = 0.089.     

Surface electronic structure of Pt(1 1 0): comparison with Ni and Pd

The unoccupied electronic structure of Pt(1 1 0) was investigated by inverse photoemission. The results were compared with the data for Ni(1 1 0) and Pd(1 1 0) with particular emphasis on surface states. The surface states in the gap of Pt(1 1 0) are shifted upwards relative to Ni and Pd, as a consequence of the (1 × 2) missing-row reconstruction. In contrast, the surface state at is only weakly affected, which indicates that it is essentially a one-dimensional state, localized on the densely-packed atomic chains on the Pt(1 1 0) surface.     

Thermal behaviour of anhydrous, dihydrate and (2/1) ethanol forms of 1-O-α- -glucopyranosyl- -mannitol

The melting points of anhydrous 1-O-α- -glucopyranosyl- -mannitol, 1-O-α- -glucopyranosyl- -mannitol dihydrate and a new compound, 1-O-α- -glucopyranosyl- -mannitol-ethanol (2/1) were determined using differential scanning calorimetry. The melting onset values were 169.2 (3), 104.3 (18) and 158.7 (9), respectively, and the melting peak values were 171.4 (5), 107.9 (15) and 160.1 (6), respectively. 1-O-α- -glucopyranosyl- -mannitol dihydrate and 1-O-α- -glucopyranosyl- -mannitol-ethanol (2/1) decompose to anhydrous form when heated at slow heating rates.According to TG-FTIR measurements, 1-O-α- -glucopyranosyl- -mannitol-ethanol (2/1) lost its ethanol in the 110–190°C range, and 1-O-α- -glucopyranosyl- -mannitol dihydrate lost its crystal water in the 60–210°C range. After removal of ethanol and crystal water, both decomposed in air totally as carbohydrates usually do, forming lower hydrocarbons with OH-groups, CO₂ and H₂O.     

螯形主体分子的设计、包结性能及其在细辛挥发油 有效成分选择分离中的应用

设计了两种新的具有螯形骨架的主体分子反式-1,2-二苯基-1,2-苊二醇(1)和顺式-1,2-二(1'-萘基)-1,2-苊二醇(2),主体(1),(2)可与许多有机小分子化合物形成配位包合物。用IR和粉末XRD表征了主体分子(1)和(2)的包结物,用^1NMR测定了包结物的主客体分子摩尔比：(1)·DMF(1:2),(1)·DMSO(1:2),(1)·THF(1:2),(1)·二氧六环(1:1),(1)·吡啶(1:1),(2)·DMF(1:1)和(2)·DMSO(1:1)。单晶X射线衍射分析了包结物的晶体结构,(1)·DMF：空间群Pnaa,a=0.9377(1)nm,b=1.4351(1)nm,c=4.0463(3)nm;(1)·DMSO：空间群Pbcn,a=1.6278(1)nm,b=1.0751(1)nm,c=1.4980(1)nm;(2)·DMF：P2~1/n,a=0.9796(1)nm,b=1.2377(1)nm,c=2.2344(3)nm,β=93.02(1)°;游离主体(1)：空间群P1,a=1.0461(1)nm,b=1.1213(1)nm,c=1.5496(1)nm,α=81.74(1)°,β=75.71(1)°,γ=89.00(1)°;分析了主体分子的刚性和柔韧性对包结性能的影响。并研究了主体分子(1)选择分离细辛挥发油,将顺甲基异丁香酚从挥发油中分离出来。     

Bioactive saponins and glycosides. XVI. Nortriterpene oligoglycosides with gastroprotective activity from the fresh leaves of Euptelea polyandra Sieb. et Zucc. (1): structures of Eupteleasaponins I, II, III, IV, V, and V acetate

The saponin fraction from the fresh leaves of Euiptelea polyandra Sieb. et Zucc. was found to exhibit potent gastroprotective activity. Fourteen new nortriterpene saponins called eupteleasaponins were isolated from the saponin fraction with gastroprotective activity. The structures of eupteleasaponins I, I1, III, IV, V, and V acetate were determined on the basis of chemical and physicochemical evidence as 3-O-alpha-L-rhamnopyranosyl(1-->2)-beta-D-glucopyranosyl(1 -->3)-beta-D-xylopyranosylakebonoic acid 28-O-beta-D-glucopyranosyl ester, 3-O-alpha-L-rhamnopyranosyl(1-->2)-[alpha-L-rhamnopyranosyl(1 -->4)-beta-D-glucopyranosyl(1-->3)-beta-D-xylopyranosylakebonoic acid 28-O-beta-D- D-glucopyranosyl(1-->3)-beta-D-xylopyranosylakebonoic acid 28-O-beta-D-glucopyranosyl ester, 3-O-alpha-L-rhamnopyranosyl(1-->2)-alpha-L-rhamnopyranosyl(1 -->4)-beta-D-glucopyranosyl(1-->3)-beta-D-xylopyranosylakebonoic acid 28-O-beta-D-glucopyranosyl ester, 3-O-alpha-L-rhamnopyranosyl(1 -->2)-[alpha-L-arabinopyranosyl(1-->4)-alpha-L-rhamnopyranosyl(1-- >4)]-beta-D- glucopyranosyl(1-->3)-beta-D-xylopyranosylakebonoic acid 28-O-beta-D-glucopyranosyl ester, 3-O-alpha-L-rhamnopyranosvl(1-->2)-[alpha-L-arabinopyranosyl (1 -->4)-beta-L-rhamnopyranosyl(1 -->4)]-beta-D-glucopyranosyl(1 -->3)-beta-D-xylopyranosylakebonoic acid, 3-O-alpha-L-rhamnopyranosyl(1 -->2)-beta-D-glucopyranosvl(1-->3)-beta-D-xylopyranosyleupteleo genin, and 3-O-alpha-L-rhamnopyranosyl(1-->2)-6"-O-acetyl-gamma-D-glucopyranosyl(1 -->3)-beta-D-xylopyranosyleupteleogenin.     

Synthesis and conjugation of oligosaccharide analogues of fragments of the immunoreactive glycan part of the circulating anodic antigen of the parasite Schistosoma mansoni

The gut-associated circulating anodic antigen (CAA) is one of the major excretory antigens produced by the parasite Schistosoma mansoni. The immunoreactive part of CAA is a threonine-linked polysaccharide composed of long stretches of the unique repeating disaccharide-->6)-[beta-D-GlcpA-(1-->3)]-beta-D-GalpNAc-(1-->. Previously, using surface plasmon resonance and ELISA techniques, it has been shown that some anti-CAA IgM monoclonal antibodies (MAbs) also recognize members of a series of bovine serum albumin (BSA)-coupled synthetic di- to penta-saccharide fragments of the CAA glycan. To generate information on the molecular level about the glycan specificity of the relevant IgM MAbs, two series of oligosaccharides related to the CAA disaccharide epitope were synthesized, and coupled to BSA. The first three analogues, beta-D-GlcpA-(1-->3)-[small beta]-D-GlcpNAc-(1-->O), beta-D-GlcpNAc-(1-->6)-[beta-D-GlcpA-(1-->3)]-beta-D-GlcpNAc-(1-->O), and beta-D-GlcpA-(1-->3)-beta-D-GlcpNAc-(1-->6)-[beta-D-GlcpA-(1-->3)]-beta-D-GlcpNAc-(1-->O), wherein the native beta-D-GalpNAc moiety was replaced by beta-D-GlcpNAc, were synthesized to investigate the specificity of the selected MAbs to the carbohydrate backbone of CAA. The second series of analogues, beta-D-Glcp6S-(1-->3)-beta-D-GalpNAc-(1-->O), beta-D-GalpNAc-(1-->6)-[beta-D-Glcp6S-(1-->3)]-beta-D-GalpNAc-(1-->O), and beta-D-Glcp6S-(1-->3)-beta-D-GalpNAc-(1-->6)-[beta-D-Glcp6S-(1-->3)]-beta-D-GalpNAc-(1-->O), wherein the native beta-D-GlcpA moiety was replaced by beta-D-Glcp6S, was synthesized to evaluate the importance of the type/nature of the charge of CAA for the MAb recognition.     

Enantioseparation of Some New 1-(2-Naphthyl)-1-ethanol Ester Derivatives by HPLC on Chiralcel OD

The direct enantiomeric resolution of racemic 2-(1H-imidazole-1-yl)-1-naphthalene-2-yl)ethanol esters, 1-(naphthalene-2-yl)ethanol esters, and 1-(1-hydroxynaphthalene-2-yl)-2-(1H-imidazole-1-yl)ethanol on silica-based cellulose tris(3,5-dimethylphenylcarbamate) (Chiralcel OD) column is described. The separations were performed using mobile phases which consist of alcohol (methanol, ethanol or 2-propanol)/n-hexane in various proportions. The effect of structural features of the solutes along with the nature and concentration of alcohol in the mobile phase on the discrimination between the enantiomers was examined for different mobile phase compositions. The results suggest that not only the structure and concentration of alcohol in the mobile phase, but also the subtle structural differences in racemates can have a pronounced effect on enantiomeric separation and retention. Baseline separations were obtained for 2-(1H-imidazole-1-yl)-1-naphthalene-2-yl)ethanol esters carrying imidazole ring in addition to ester functional group in their structures. The α values of the resolved enantiomers of 2-(1H-imidazole-1-yl)-1-naphthalene-2-yl)ethanol esters were in the range of 1.49–1.62 while the R _s values varied from 4.20 to 6.75 when methanol/n-hexane (70:30 v/v) was used as mobile phase.

     

Studies on intramolecular 1,3-dipolar cycloaddition reactions: III. The synthesis of a novel heterocyclic ring system by regiospecific cycloaddition

The syntheses of a number of C-aryl-N-3-butenyl nitrones [aryl ring=4-CH₃O-phenyl ( 1a ), phenyl ( 1b ), 4-Cl-phenyl ( 1c ), 4-Br-phenyl ( 1d ), 4-NO₂-phenyl ( 1e ), 2-furyl (1f), 2-thienyl ( 1g ), 2-pyrryl ( 1h )] and their thermochemical reactions have been investigated. The thermocycloadditions of 1a–1h are regiospecific in forming a novel heterobicyclic ring system, exo-aryl-1-aza-7-oxabicyclo-[2.2.1]heptane.     

Synthesis and Crystal Structure of a New Sulfur-Palladium-Nitrogen Complex

The reaction of 4-amino-6-methyl-1,2,4-triazine-3(2H)-thione-5-one (AMTTO, 1 ) with palladium(II) chloride in acetonitrile/methanol leads to the N,S-coordinated complex [Pd(η²-AMTTO-N,S)Cl₂] · CH₃OH ( 2 ). 2 has been characterized by IR and MS techniques. The ligand 1 and the complex 2 were also investigated by X-ray structure determinations. 1 crystallizes in the space group P1¯ with the lattice dimensions at –70 °C: a = 419.6(1), b = 598.2(1), c = 1351.3(1) pm, α = 92.23(1), β = 91.20(1), γ = 100.51(1)°, Z = 2, R₁ = 0.0441. 2 crystallizes in the space group P2₁/c with the lattice dimensions at 20 °C: a = 683.3(1), b = 1323.0(1), c = 1254.2(1) pm, β = 92.61(1)°, Z = 4, R₁ = 0.0361. According to the structure analysis 1 consists of planar C,N-heterocycles connected by hydrogen bridges forming an infinite chain along [110]. The basic heterocyclic skeleton of 2 is essentially planar and linked three-dimensionally through hydrogen bridges.     

Experimental Investigations on Highly Conducting Solid Bio-Polymer Electrolytes Based on Latex of Calotropis gigantea Plant

The study has prepared highly conducting polymer electrolyte films using solution cast technique with poly(vinylidene fluoride-co-hexafluoropropylene) PVDF-HFP, mixture of ethylene carbonate (EC), and propylene carbonate (PC) as plasticizer and latex of Calotropis gigantea (CGL) as an ionic source. In this study, four films are prepared using PVDF-HFP:CGL in ratio 1:1 with the increasing concentration of EC+PC as 1, 2, 3, and 4 M named as 1:1:1, 1:1:2, 1:1:3, 1:1:4. The prepared polymer electrolyte is examined by polarized optical microscopy (POM), elemental dispersive X-ray technique (EDX), and complex impedance spectroscopy. EDX and POM are studied for the surface morphology of all prepared samples and to investigate the porous nature of films. The enhancement in ionic conductivity occurs due to CGL and increasing amount of EC-PC. Conductivity of highest composition (1:1:4) polymer electrolyte film is found to be ≈10⁻³ S cm⁻¹. The optimized polymer electrolyte film is considered as a promising candidate for application in supercapacitors.     

Gas-phase kinetics of elimination reactions of pentane-2,4-dione derivatives. Part ii [1]. Thermolysis of derivatives and analogues of 3-phenylhydrazonopentane-2,4-dione

Six analogues and derivatives (1–6) of 3-phenylhydrazonopentane-2,4-dione (7) were subjected to gas-phase thermolysis. The Arrhenius log A (s⁻¹) and Ea (kJ mol⁻¹) of the analogues (1–5) are, respectively: 10.42 and 140.8 for 1-cyano-1-phenyl-hydrazonopropanone (1) , 11.19 and 135.4 for 1-cyano-1-( -nitrophenylhydrazono)-propanone (2) , 10.68 and 144.9 for 1-cyano-1-( -methoxyphenylhydrazono)propanone (3) , 11.76 and 137.8 for 1-cyano-3-phenyl-1-phenylhydrazonopropanone (4) , and 11.29 and 145.9 for 1-cyano-1-phenylhydrazonobutanone (5) . The corresponding values for ethyl 3-oxo-2-phenylhydrazonobutanoate (6) are 11.90 s⁻¹ and 143.3 kJ mol⁻¹. The rates of reaction at 600 K are compared with those of the title diketone (7) and of pentane-2,4-dione (8) and rationalized in terms of a plausible elimination pathway involving a semiconcerted six-membered transition state. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet: 30: 457–462, 1998     

The adsorption of 1,3-butadiene on Pd/Ni multilayers: The interplay between spin polarization and chemisorption strength

The adsorption of 1,3-butadiene (BD) on the Pd/Ni(1 1 1) multilayers has been studied using the VASP method in the framework of the density functional theory (DFT). The adsorption on two different configurations of the Pd_n/Ni_m(1 1 1) systems were considered. The most stable adsorption sites are dependent on the substrate composition and on the inclusion or not of spin polarization. On Pd₁Ni₃(1 1 1) surface, di-π-cis and 1,2,3,4-tetra-σ adsorption structures are the most stable for non-spin polarized (NSP) and spin polarized (SP) levels of calculation, respectively. Conversely, on Pd₃Ni₁(1 1 1) surface, the 1,2,3,4-tetra-σ adsorption structure is the most stable for both NSP and SP levels, respectively. The magnetization of the Pd atoms strongly modifies the adsorption energy of BD and its most stable adsorption mode. On the other hand, as a consequence of BD adsorption, the Pd magnetization decreases. The smaller adsorption energies of BD and 1-butene on the Pd₁Ni₃(1 1 1) surface than on Pd(1 1 1) can be associated to the strained Pd overlayer deposited on Ni(1 1 1).     

Complete 1H and 13C NMR assignments for two new monodesmoside saponins from Pentaclethra macroloba (Willd.) Kuntze

A detailed NMR study and full assignments of the 1H and 13C spectral data for two novel triterpenoid saponins isolated from the stem bark of Pentaclethra macroloba (Willd.) Kuntze are described. Their structures were established using a combination of 1D and 2D NMR techniques including 1H,1H-COSY, TOCSY, NOESY, gs-HMQC and gs-HMBC, and also electrospray ionization mass spectrometry and chemical methods. The structures were established as 3beta-O-([O-beta-D-glucopyranosyl-(1-->2)-O-beta-D-glucopyranosyl-(1-->4)-O-beta-D-glucopyranosyl-(1-->3)-O-alpha-L-rhamnopyranosyl-(1-->2)]-[O-beta-D-glucopyranosyl-(1-->3)-O-beta-D-glucopyranosyl-(1-->4)])-alpha-L-arabinopyranosylhederagenin (1) and 3beta-O-)[O-beta-D-glucopyranosyl-(1-->2)-O-beta-D-glucopyranosyl-(1-->4)-O-beta-D-glucopyranosyl-(1-->3)-O-alpha-L-rhamnopyranosyl-(1-->2)]-[O-beta-D-glucopyranosyl-(1-->3)-O-beta-D-glucopyranosyl-(1-->4)])-alpha-L-arabinopyranosyloleanolic acid (2).