The first indium-organic two-dimensional layer network with rhombus grids

The indium(III)-organic compound [In(HBtc)₂(4,4′-bpy)](4,4′-Hbpy)(H₂O)_0.5 (Btc=1,3,5-benzenetricarboxylate, 4,4′-bpy=4,4′-bipyridine) has been synthesized under hydrothermal condition and characterized by IR, fluorescent spectroscopy, TGA and single-crystal X-ray diffraction analyses. The compound crystallizes in monoclinic, space group P2(1)/c, a=17.0884(2) Å, b=12.28390(10) Å, c=17.9456(4) Å, β=104.1920(10)°, V=3652.03(10) Å³, Z=4, R₁=0.0572 and wR₂=0.1116 [I>2σ(I)]. All the indium atoms in the compound are hepta-coordinated and link 1,3,5-benzenetricarboxylate forming a 2-D layer structure with rhombus grids.     

Polarographic determination of Ce(III) and Tm(III) using rare earth-DBF-chlorophosphonazo complex

The electrochemical behaviour of the DBF—chlorophosphonazo (DBF—CPA)—rare earth (RE) complex has been investigated in this paper. A highly sensitive polarographic adsorption wave was found in the RE(III)—DBF—CPA system and a new method for determination of trace total RE(III) has been established. The limit of detection was 1.8 × 10⁻⁸M. The results of determination of the total RE(III) content in Chinese standard reference materials of cast-iron and alloy steel were in good agreement with the certified values. The polarographic adsorptive waves of Ce(III) and Tm(III)—DBF—CPA overlap seriously. In order to improve the selectivity of determination, a non-linear regression model was employed to fit the peak height of the polarographic wave and the concentrations of Ce(III) and Tm(III). The predictive accuracy of this model for simulant mixtures was satisfied.     

Tocopherols and Triterpenoids from Sida acuta

A new tocopherol derivative, 7_a‐methoxy‐α‐tocopherol ( 1 ), and a new taraxastane triterpene, taraxast‐1,20(30)‐dien‐3‐one ( 5 ), together with four known compounds, β‐tocopherol ( 2 ), α‐tocopherol ( 3 ), α‐tocospiro B ( 4 ) and taraxasterone ( 6 ) were isolated from the whole plant of Sida acuta. Their structures were elucidated by spectral analysis including MS, 1D and 2D‐NMR spectroscopy. Among those compounds, compounds 1 , 2 , and 3 showed significant antioxidant effect (EC₅₀ = 86.9, 68.2, and 70.9 μM, respectively) in the DPPH radicals scavenging activity assay.     

CHLOROPHYLL PHOTOSENSITIZED ELECTRON TRANSFER IN PHOSPHOLIPID VESICLE SYSTEMS: COMPARISON OF INSIDE-OUTSIDE ASYMMETRY BETWEEN LARGE AND SMALL UNILAMELLAR VESICLES*

Abstract— We have determined the chlorophyll triplet quenching efficiencies, the chlorophyll cation radical yields and the conversion efficiencies of chlorophyll triplet to radical in large and small unilamellar phosphatidylcholine vesicles (LUV and SUV, respectively) in the presence of electrically-charged electron acceptors (ferricyanide and oxidized cytochrome c) located in either the inner or outer aqueous compartments of the vesicles. Both types of vesicles displayed inside-outside asymmetry, although the properties were reversed. Triplet quenching in SUV was more efficient when ferricyanide was located within the vesicle interior, whereas the reverse was true in LUV. When ferricyanide was located on the outside of the vesicles, the extent of triplet quenching in LUV was about two times that in SUV and the amount of cation radical formed in LUV was about two times that in SUV. Under these conditions, the conversion efficiencies of chlorophyll triplet to radical were 12.2% for LUV and 8.5% for SUV. With cytochrome c as an electron acceptor in negatively charged vesicles (25 mol per cent dixhexadecylphosphate incorporated) similar results were obtained. Again, the triplet quenching and radical yield inside-outside asymmetry properties were reversed between the two types of vesicles, and radical formation efficiencies when cyt c was located outside the vesicles were higher in LUV (11.7%) than in SUV (4.2%). We conclude that the inside-outside asymmetric photochemical behavior of unilamellar phosphatidylcholine vesicles is influenced by factors in addition to the difference in radius of curvature between the inside and outside surfaces. It is suggested that transmembrane electrostatic potentials may be involved. Furthermore, in the present system the properties of LUV were more favorable to photochemical electron transfer product formation than those of SUV.     

Preparation of multihollow P(St-MAA) particles by sequence soap-free/soap emulsion polymerization and followed by stepwise alkali/acid posttreatment

The effects of ionic emulsifier, sodium dodecylbenzene sulfate (SDBS), on the formation of the multihollow structures in sub-micron sized polymer particles produced by alkali/acid posttreatment were investigated. The original latex particles with narrow size distribution were synthesized by a new sequence emulsifier-free/emulsifier emulsion copolymerization of styrene (St) and methacrylic acid (MAA). Results indicated that the pore size decreased and the pore number increased with the increase of SDBS amount, and the morphology of the posttreated latex particles was also significantly influenced by the introducing time of SDBS in the preparation of the original latex particles, and a suitable introducing time was 3 h of polymerization.     

Two New Steroidal Glycosides from Fermented Leaves of Agave americana

Two new spirostanol glycosides named agamenoside A and B, ere isolated from the fermented leaves of Agave americana. Their structures were elucidated as (23S,25R)-5α-spirostan-3β,6α，23－triol 3-O-α-L-rhamnopyranosyl-(1→3)-β-D-glucopyranosyl-(1→2)-[β-D-xylopyranosyl-(1→3)]-β-D-glucopyranosyl-(1→4)-β-D-galactopyranoside(1) and (25R)-5α-spiro-stan-3β,6α-diol 3-O-β-D-glucopyranosyl-(1→2)-[β-D-xylopyranosyl-(1→3)]-β-D-glucopyra-nosyl-(1→4)-β-D-galactopyranoside(2) by a combination of chemical and spectral methods.     

Synthesis of （2R,4R）—2—N—tert—Butyloxycarbonyl Amino—4,5—epoxido—valeric Acid Methyl Ester

The stereoselective synthesis of (2R,4R)-2-N-tert-butyloxycarbonyl amino-4,5-epoxido-valeric acid methyl ester 8,which is the key intermediate for the synthesis of (2′S,2R)-3-trans-nitrocyclopropyl-alanine,was first accomplished.     

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…     

π -Type and σ -type cation- π complexes of atomic cations

MP2/6-31+G* calculations were performed on the cation- complexes of ethylene, cyclobutadiene and benzene with a number of atomic cations. It was found that except B⁺ all the atomic cations form -type cation- complexes with ethylene. On the other hand, with cyclobutadiene Li⁺, N⁺, Na⁺, P⁺ and K⁺ form -type complexes, whereas H⁺, F⁺, and Cl⁺ form covalent -type complexes. With benzene Li⁺, B⁺, Na⁺, Al⁺, and K⁺ form -type complexes whereas H⁺, F⁺, and Cl⁺ form -type complexes. It was concluded that the driving force to form the -type complex is chemical bonding, and that for metal cations to form -type complexes is non-covalent interaction.     

可再生甲壳素吸附铬（Ⅵ）的特性研究

可再生甲壳素吸附铬（Ⅵ）的特性研究陈炳稔＊汤又文李国明万春华（华南师范大学化学系广州５１０６３１）关键词可再生甲壳素，制备，铬（Ⅵ），吸附１９９７－０８－１９收稿，１９９７－１２－２３修回广东省科委及高教厅资助课题利用甲壳素作为铬（Ⅵ）的捕集剂已有报...