Preparation of a zwitterionic trichloroplatinum(II) complex with an alkylbipyridinum ligand and its reaction in dmso-<Emphasis Type="BoldItalic">d</Emphasis><Subscript>6</Subscript> solution

A zwitterionic trichloroplatinum(II) complex PtCl₃(4,4′-bpy-N-ⁿBu) (1) was prepared by an aqueous reaction of [4,4′-bpy-N-ⁿBu]Cl with K₂PtCl₄, and was characterized by ¹H-n.m.r. and IR spectroscopy as well as elemental analysis. Dissolving (1) into dmso-d ₆ at 25 °C yields a mixture of the complexes, cis-PtCl₂(4,4′-bpy-N-ⁿBu)(dmso-d ₆) (2-cis), trans-PtCl₂(4,4′-bpy-N-ⁿBu)(dmso-d ₆) (2-trans), [4,4′-bpy-N-ⁿBu]Cl and PtCl₂(dmso-d ₆)₂. Ratio of the products in the dmso-d ₆ solution changed depending on the temperature and the total concentration of the complexes. These compounds are in equilibrium via isomerization reaction between (2-cis) and (2-trans) and via displacement reaction of the alkylbipyridinium ligand of (2-cis) and (2-trans) with dmso-d ₆ to form [4,4′-bpy-N-ⁿBu]Cl and PtCl₂(dmso-d ₆)₂.     

Spectroscopic studies of bridged binuclear complexes of Co(II), Ni(II), Cu(II) and Zn(II)

Binuclear cobalt(II), nickel(II), copper(II) and zinc(II) complexes of general composition [M₂L^1-2(μ-Cl)Cl₂] · nH₂O with the Schiff-base ligands (where L¹H and L²H are the potential pentadentate ligands derived by condensing 2,6-diformyl-4-methylphenol with 4-amino-3-antipyrine and 2-hydroxy-3-hydrazinoquinoxiline, respectively) have been synthesized and characterized. Analytical and spectral studies support the above formulation. ¹H-NMR and IR spectra of the complexes suggest they have an endogenous phenoxide bridge, with chloride as the exogenous bridge atom. The electronic spectra of all the complexes are well characterized by broad d–d and a high intensity charge-transfer transitions. The complexes are chloro-bridged as evidenced by two intense far-IR bands centered around 270–280 cm⁻¹. Magnetic susceptibility measurements show that complexes are antiferromagnetic in nature. The compounds show significant growth inhibitory activity against fungi Aspergillus niger and Candida albicans and moderate activity against bacteria Bacillus cirroflagellosus and Pseudomonas auresenosa.     

2-Amino-4-bromobutanoic Acid

(2S)- and (2R)-2-Amino-4-bromobutanoic acid were prepared starting from N-Boc-glutamic acid α tert-butyl ester. The double tert-butyl protection was necessary to prevent a partial racemisation during Barton’s radical decarboxylation used to transform the γ-carboxylic group into a bromide. This bromide reacted with different nitrogen, oxygen and sulphur nucleophiles to give nonnatural amino acids characterised by basic or heterocyclic side chains. The title compound was also used to prepare a conformationally constrained peptidomimetic.     

Steroidal saponins from rhizomes of Tupistra wattii Hook. f

Chemical examination of the fresh rhizomes of Tupistra wattii HOOK. f. led to the isolation of three new steroidal saponins, wattoside G (1), H (2), and I (3), together with one known steroidal saponin, (25S)-1beta,3beta,4beta-trihydroxyspirotan-5beta-yl-O-beta-D-glucopyranoside (4). The structures of 1-3 were established to be (25R)-1beta,2beta,3beta,5beta-tetrahydroxyspirostan-4beta-yl-O-beta-D-xylopyranoside (1), (24S,25S)-24-[(beta-D-glucopyranosyl)oxy]-1beta,2beta,3beta,4beta,5beta,7beta-hexahydroxyspirostan-6-one (2), and (24S,25S)-1beta,3beta-dihydroxy-5beta-spirostan-24-yl-O-beta-D-glucopyranosyl-(1-->6)-beta-D-glucopyranoside (3) on the basis of detailed analyses of physical, chemical, and spectral data. The isolated compounds were evaluated for cytotoxic activity against the cancer cell line K562 in vitro.     

环己烷催化氧化制取顺酐和醋酸的催化剂研究

为研究气态环己烷催化氧化制取顺酐及醋酸的新反应，采取不同的方法制备了系列固体VPO催化剂.借助XRD、FT-IR对催化剂进行了主体晶相确定，用氧化还原滴定方法测定了不同晶相催化剂中钒的平均氧化数.结合催化反应的活性评价，发现催化剂主体晶相、结晶度、活化气氛和催化剂的V4＋/V5＋比均对目标反应的催化活性产生影响，5种催化剂中以(VO)2P2O7晶相催化剂的活性为最高.     

Dinickel Complexes Bridged by Unusual (N,O,O′)-Coordinated α-Amino Acids: Syntheses,Structural Characterization and Magnetic Properties

Four novel dinickel complexes, coordinated by mixed ligands of tren and racemic amino acids, namely [Ni₂(tren)₂(dl-alaninato)(H₂O)]I₃·2H₂O (1), [Ni₂(tren)₂(dl-leucinato)(H₂O)]I₃·2.5H₂O (2), [Ni₂(tren)₂(dl-phenylalaninato)(H₂O)]I₃·H₂O (3), and {[Ni₂(tren)₂(dl-histinato)](ClO₄)₃·1.5H₂O} _n (4), have been synthesized and structurally characterized by X-ray crystallography, FTIR, u.v. and e.s. spectra. They represent the first series of dinickel(II) complexes bridged by the unusual (N,O,O)-coordinated -amino acids. In complexes (1–3), one of the nickel(II) centers is coordinated by four N-atoms of the tren ligand, one O-atom of the carboxylate group of the amino acidato ligand and one H₂O molecule. The other nickel(II) center is also coordinated by the four N-atoms of the tren ligand, one carboxylic O-atom and the amino N-atom of the amino acidato ligand, resulting in an asymmetric dinuclear core with chromophores of NiN₄O₂ and NiN₅O. In the polymeric {[Ni₂(tren)₂(dl-histinato)](ClO₄)₃·1.5H₂O} _n (4), the imidazole N-atom is also involved in ligation with nickel(II) and both nickel(II) centers have the same chromophore described as NiN₅O. The Ni...Ni distances are in the 5.5199(10)–5.5807(15)Å range. Analyses of the magnetic properties of complexes (1), (3) and (4) show that a weak ferromagnetic interaction exists between the two nickel(II) centers.     

Determination of the Dissociation Constants of Urocanic Acid Isomers in Aqueous Solutions

Summary. (E)- and (Z)-Urocanic acids are endogenous chemicals in the normal mammalian skin. The first and the second thermodynamic dissociation constants (pK _a1 and pK _a2) of urocanic acid isomers were determined using UV spectrophotometry in aqueous solutions. The values with standard deviation (pK _a1 = 3.43 ± 0.12 and pK _a2 = 5.80 ± 0.04) and (pK _a1 = 2.7 ± 0.3 and pK _a2 = 6.65 ± 0.04) were obtained to (E)- and (Z)-urocanic acids, respectively. The second dissociations were studied also by potentiometric titration in aqueous sodium chloride solutions up to the isotonic salt concentration (0.154 mol dm⁻³), and the second thermodynamic dissociation constants as well as activity parameters for both isomers were determined at temperature 25°C and for (E)-urocanic acid also at 37°C. The obtained pK _a2 values were close to those found by UV spectrophotometry. The equations for the calculation of the second stoichiometric dissociation constants of urocanic acid isomers on molality and molarity scale in aqueous sodium chloride solutions were derived. The obtained pK _a1 and pK _a2 values for (Z)-urocanic acid appear to be essentially lower than some previously reported values in literature. An erratum to this article is available at .     

Conductivity Studies of <Emphasis Type="Italic">n</Emphasis>-Tetrabutylammonium Tetraphenylborate in 3-Pentanone in the Temperature Range from 283.15 to 329.15 K

The molar conductivities (Λ) of solutions of n-tetrabutylammonium tetraphenylborate (NBu₄BPh₄) in 3-pentanone have been measured in the temperature range from 283.15 to 329.15 K. The conductance data have been analyzed using the Lee-Wheaton conductivity equation with the distance parameter (a) set at Bjerrum’s pairing distance, and the limiting molar conductivities (Λ_o) and the association equilibrium constants (K _A) have been derived. The limiting ion conductivities (λ_±^o) have been evaluated according to the method of Krumgalz. The λ₊ ^o values have been compared with λ₊ ^o values calculated from the empirical equation of Gill. The thermodynamic functions, Gibbs energy (Δ G _A ^o), enthalpy (Δ H _A ^o) and entropy (Δ S _A ^o) for the process of ion-pair formation as well as the activation energy of the ionic movement (ΔH ^∗) have been evaluated. The obtained results are discussed in terms of ion-ion and ion-solvent interactions.     

大挠度弯曲直梁混合变量最小势能原理的应用

应用大挠度弯曲直梁混合变量最小势能原理,求解均载两端固定大挠度柱面弯曲板条的轴向挠度分布和轴向弯矩分布．实例计算表明:该方法简单实用、精度高,是一种计算大挠度柱面弯曲板条变形的有效方法．     

In vivo mechanical study of helical cardiac pacing electrode interacting with canine myocardium

Cardiac pacing is a medical device to help human to overcome arrhythmia and to recover the regular beats of heart. A helical configuration of electrode tip is a new type of cardiac pacing lead distal tip. The helical electrode attaches itself to the desired site of heart by screwing its helical tip into the myocardium. In vivo experiments on anesthetized dogs were carried out to measure the acute interactions between helical electrode and myocardium during screw-in and pull-out processes. These data would be helpful for electrode tip design and electrode/myocardium adherence safety evaluation. They also provide reliability data for clinical site choice of human heart to implant and to fix the pacing lead. A special design of the helical tip using strain gauges is instrumented for the measurement of the screw-in and pull-out forces. We obtained the data of screw-in torques and pull-out forces for five different types of helical electrodes at nine designed sites on ten canine hearts. The results indicate that the screw-in torques increased steplike while the torque–time curves presente saw-tooth fashion. The maximum torque has a range of 0.3–1.9 N mm. Obvious differences are observed for different types of helical tips and for different test sites. Large pull-out forces are frequently obtained at epicardium of left ventricle and right ventricle lateral wall, and the forces obtained at right ventricle apex and outflow tract of right ventricle are normally small. The differences in pull-out forces are dictated by the geometrical configuration of helix and regional structures of heart muscle.