Tuning the oxidation properties of vanadium(V) through ligand stoichiometry

Vanadium(V) (5 mol %) and hydroxamic acid ligand (45 mol %) were found to promote the selective tert-butyl hydroperoxide-mediated oxidation of allylic and propargylic alcohols to the corresponding aldehydes and ketones.     

Valence bond theoretical study for chemical reactivity

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芦荟中多糖的光度测定新方法

利用正交试验考察了芦荟多糖与刚果红显色反应的最佳条件；研究了麦芽糖糊精等多糖、蔗糖等低聚糖和葡萄糖等单糖对显色反应的影响；建立了简便快速、常见糖类基本无干扰的测定芦荟多糖含量的吸光光度法。对芦荟鲜叶和芦荟制品中的多糖进行分析，加标回收率在92％～96％范围内，相对标准偏差≤5％。     

饱和锌的粘土矿物吸附半胱氨酸的机理

用红外光谱、X射线衍射（XRD）和热分析研究了饱和过渡金属锌的粘土矿物吸附半胱氨酸的机理；XRD结果显示吸附了半胱氨酸后的粘土矿物的d(001)方向的距离明显增大，说明被吸附的半胱氨酸进入了粘土的层状结构之中；饱和了锌的粘土矿物吸附半胱氨酸有两种方式，其一为弱相互作用，另一种强相互作用；后一种方式吸附的半胱氨酸与粘土的过渡金属之间形成了配合结构，结合力比较强，在热作用下，它们一直到395℃左右才分解；强相互作用吸附的半胱氨酸主要是以去质子的两性离子和阴离子形式存在于粘土矿物上，与过渡金属形成螯合的六元环结构。     

CTMAB胶束体系中反离子缔合度的测定

对十六烷基三甲基淡化按（CTMAB）水胶束体系，不同方法测得其反离子缔合度产值不同【‘－＼且很高于由股团电化学理论所得q值0．67问．本文以离子选择性电极法测定CTMAB水胶束体系中反离子缩合度（仁0．65），并研究了外加盐和乙醇的影响·1实验部分1．工试剂和仪器十六烷基三甲基漠化技（CP）在无水乙醇中重结晶两次，纯化物经帕环法测其表面张力在CMC附近无最低声、·淡化钾（AR），水为。次蒸馏水，PXJIC型离子计，302型PB，电极（响应范围为PB，＝1．6～3．3，响应时间为5分钟）222型甘汞电极·1．2实验方法在CMCV／de的稀…     

Surface-modified CdSe quantum dots as luminescent probes for cyanide determination

Luminescent surface-modified CdSe semiconductor quantum dots (QDs), with nanoparticle (NP) size distribution in the order of 2-7 nm, have been synthesized for optical determination of cyanide ions. The nanoparticles have been functionalised with tert-butyl-N-(2-mercaptoethyl)-carbamate (BMC) groups and exhibit a strong fluorescent emission at about 580 nm with rather long fluorescence lifetimes (several hundred nanoseconds) in aerated methanolic solution. The observed luminescence emitted by the synthesized nanocrystals was tremendously increased by photo-activation under sunlight exposure. The functionalised QDs turned out to exhibit excellent long-term stability when stored in the dark (no significant changes in QDs luminescence emission intensity was observed even after two months from synthesis). The functionalisation of the NPs with carbamate ligand allowed a highly sensitive determination of free cyanide via analyte-induced changes in the photoluminescence (fluorescence quenching of intensity at 580 nm and lifetime changes) of the modified quantum dots (excited at 400 nm). A detection limit of 1.1 × 10⁻⁷ M (2.9 μg l⁻¹) of cyanide ions was obtained, while the interfering effect of other inorganic anions (including NO₃⁻, Cl⁻ or SCN⁻) was negligible even at 200-fold level concentrations in excess of cyanide.     

Flow-injection chemiluminescence determination of chloroquine using peroxynitrous acid as oxidant

A new flow-injection chemiluminescence (CL) method for determination of chloroquine is proposed based on a stronger chemiluminescence of chloroquine in hydrogen peroxide-nitrite-sulfuric acid medium. The proposed method allows the measurement of chloroquine over the range of 3.0×10⁻⁷ to 1.0×10⁻⁵ mol l⁻¹. The detection limit is 8.6×10⁻⁸ mol l⁻¹, and the relative standard deviation for 1.0×10⁻⁶ mol l⁻¹ chloroquine (n=11) is 1.6%. The CL mechanism is also discussed.     

Further Daphniphyllum Alkaloids from the Leaves of Daphniphyllum macropodum Miq.

Five new polycyclic Daphniphyllum alkaloids, macropodumines F ( 1 ) and G ( 2 ), 17‐oxoyuzurimine ( 3 ), and macropodumines H ( 4 ) and I ( 5 ), were isolated from the leaves of D. macropodum Miq ., collected in Sichuan Province, China. The structures and relative configurations of the new compounds – as well as of four known, related alkaloids – were elucidated on the basis of in‐depth spectroscopic and mass‐spectrometric analyses, by chemical derivatization, and by comparison of spectroscopic data with those of known compounds.     

Dynamical intramolecular metal-to-metal ligand exchange of phosphine and thioether ligands in derivatives PtRu5(CO)16(mu6-C)

The complexes PtRu(5)(CO)(15)(PMe(2)Ph)(mu(6)-C) (2), PtRu(5)(CO)(14)(PMe(2)Ph)(2)(mu(6)-C) (3), PtRu(5)(CO)(15)(PMe(3))(mu(6)-C) (4), PtRu(5)(CO)(14)(PMe(3))(2)(mu(6)-C) (5), and PtRu(5)(CO)(15)(Me(2)S)(mu(6)-C) (6) were obtained from the reactions of PtRu(5)(CO)(16)(mu(6)-C) (1) with the appropriate ligand. As determined by NMR spectroscopy, all the new complexes exist in solution as a mixture of isomers. Compounds 2, 3, and 6 were characterized crystallographically. In all three compounds, the six metal atoms are arranged in an octahedral geometry, with a carbido carbon atom in the center. The PMe(2)Ph and Me(2)S ligands are coordinated to the Pt atom in 2 and 6, respectively. In 3, the two PMe(2)Ph ligands are coordinated to Ru atoms. In solution, all the new compounds undergo dynamical intramolecular isomerization by shifting the PMe(2)Ph or Me(2)S ligand back and forth between the Pt and Ru atoms. For compound 2, DeltaH++ = 15.1(3) kcal/mol, DeltaS++ = -7.7(9) cal/(mol.K), and DeltaG(298) = 17.4(6) kcal/mol for the transformation of the major isomer to the minor isomer; for compound 4, DeltaH++ = 14.0(1) kcal/mol, DeltaS++ = -10.7(4) cal/(mol.K), and DeltaG(298) = 17.2(2) kcal/mol for the transformation of the major isomer to the minor isomer; for compound 6, DeltaH++ = 18(1) kcal/mol, DeltaS++ = 21(5) cal/(mol.K) and DeltaG(298) = 12(2) kcal/mol. The shifts of the Me(2)S ligand in 6 are significantly more facile than the shifts for the phosphine ligand in compounds 2-5. This is attributed to a more stable ligand-bridged intermediate for the isomerizations of 6 than that for compounds 2-5. The intermediate for the isomerization of 6 involves a bridging Me(2)S ligand that can use two lone pairs of electrons for coordination to the metal atoms, whereas a tertiary phosphine ligand can use only one lone pair of electrons for bridging coordination.