The crystal and molecular structure of the β-cyclodextrin inclusion complex with aspirin and salicylic acid

The crystal structure of the -cyclodextrin (-CyD) molecular complex with aspirin (acetylsalicylic acid), salicylic acid, and water, (C₄₂H₇₀O₃₅)₂ (C₉H₈O₄)₂ (C₇H₆O₃) 23.3H₂O, was determined by X-ray structure analysis. The crystal data is space group Pl, a=19.777(5), b=15.247(3), c=15.475(4) Å, =102.63(2)°, =116.96(2)°, =104.12(2)°, V=3729(2) ų, D_m=1.409(2) g/cm³, D_X=1.419 g/cm³, and Z=1. The two -CyDs form a dimer unit with hydrogen bond networks among the secondary hydroxyl groups of both -CyDs. This -CyD dimer includes three guest molecules of two different types in its hydrophobic cavity. Two of them are aspirin, which are separately included in each cavity of the -CyD unit, with their hydrophobic benzene rings protruding into the hydrophobic cavities of the host -CyDs. The remaining guest molecule is the hydrolyzed product of an aspirin, that is salicylic acid, which is sandwiched in the space constructed by the -CyD dimer formation, and is statistically disordered at three sites.     

Reaction of ruthenium carbonylcarbide cluster Ru6C(CO)17 with nickelocene and pentamethylcyclopentadiene

The reaction of cluster Ru₆C(CO)₁₇ (1) with nickelocene is studied. Five CO ligands rather than a metal-ligand crown are substituted for two cyclopentadienyl groups to give a new complex Ru₆C(⁵-Cp)₂(CO)₁₂ (2). The reaction of cluster1 with entamethylcyclopentadiene leads to new complex Ru₆C(-¹⁵-CH₂C₅Me₄)(CO)₁₄ (3) containing the cr-bond CH₂-Ru, along with an ⁵-coordinated cyclopentadienyl ring.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1171–1172, June, 1995.     

Critical discussion of simple adsorption methods used to evaluate the micropore size distribution

The well-known simple adsorption methods used to evaluate the micropore size distribution from low pressure adsorption isotherms were examined by employing model isotherms for slit-like graphite micropores obtained from nonlocal density functional theory. It was shown that in the range of pore sizes from about 0.4 to 0.9 nm, the Horvath Kawazoe (HK) method satisfactorily reproduces the shape of the micropore size distribution, but the pore sizes are underestimated. In the case of micropores wider than 0.9 nm, the method fails as the formation of the monolayer on the pore walls produces a peak corresponding to 0.6 nm micropores on the HK pore size distribution. Therefore, the HK method indicates the presence of microporosity even for nonporous samples. The Dubinin-Astakhov adsorption isotherms were also examined and it was shown that their application to represent local adsorption isotherms for homogeneous pores is questionable. However, the adsorption potential distributions seem to be promising for micropore analysis.Nomenclature A Adsorption potential kJ/mol - C ₁ Constant in Eq. 3 and 4 kJ * nm/mol - C ₂ Constant in Eq. 3 and 4 nm³ - C ₃ Constant in Eq. 3 and 4 nm⁹ - C ₄ Constant in Eq. 3 and 4 - d Adsorbate molecule diameter nm - d _A Adsorbent atom diameter nm - G Change in the Gibbs free energy kJ/mol - J Pore size distribution cm³/(g*nm) - R The universal gas constant = 8.31431 J/(mol * K) - T Absolute temperature K - V Amount adsorbed expressed in cm³ of liquid adsorbate per 1 g of the adsorbent = 0.0015468 * amount adsorbed expressed in cm³ STP/g cm³/g - x Pore width nm - X Differential adsorption potential distribution cm³ * mol/(g*kJ) - Constant defined as nm - p Pressure Pa - p ₀ Saturated pressure = 760 torr = 101325 Pa Pa - P _c Condensation pressure Pa - Degree of pore filling - S _BET BET specific surface area m²/g - S _ex External surface area obtained fromt-plot method m²/g - V _mi Micropore volume obtained fromt-plot method cm³/g - V ₁ Total pore volume cm³/g - E Characteristic energy in the Dubinin-Astakhov equation kJ/mol - n Exponent in the Dubinin-Astakhov equation      

Triterpenoid Glycosides of Fatsia japonica. II. Isolation and Structure of Glycosides from the Leaves

The previously known triterpenoid 3-O--L-arabinopyranosides of oleanolic and echinocystic acids and hederagenin, 3-O--D-glucopyranosyl-(12)-O--L-arabinopyranosides of oleanolic acid and hederagenin, in addition to 28-O--L-rhamnopyranosyl-(14)-O--D-glucopyranosyl-(16)-O--D-glucopyranosyl ethers of the 3-O--L-arabinopyranoside of hederagenin, and 3-O--D-glucopyranosyl-(12)-O--L-arabinopyranosides of oleanolic acid and hederagenin, respectively, are isolated from leaves ofFatsia japonica(Araliaceae). The structures of the glycosides are confirmed by chemical methods and ¹³ C NMR spectroscopy     

Pulse photolysis of ditertbutyl peroxide in benzene

The method of pulse photolysis has been used to determine termination rate constants of primary peroxy radicals in benzene at 295 K. Radicals CH₃O ₂ ^. have been found to decay with the rate constant 2k₆=3.7×10⁸ M^–1 s^–1 and radicals (CH₃)₃ COOC(CH₃)CH₂O ₂ ^. with 2k₈=1.2×10⁸ M^–1 s^–1, the rate constant of cross-recombination for both radicals being 2.4×10⁸ M^–1 s^–1.

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295 K: CH₃O ₂ ^. 3,7·10⁸ (M·c)^–1, (CH₃)₃COOC(CH₃)₂CH₂O ₂ ^. =qt 1,2·10⁸ (M·c)^–1, 2,4·10⁸ (M·c)^–1.

     

Wettability of Microstructured Hydrophobic Sol-Gel Coatings

The formation of appropriate surface patterns on hydrophobic surfaces leads to a general change in their wettability and the contact angle increases substantially. Such coatings are of great technical interest, especially if aqueous media are concerned as in the prevention of ice-adhesion. For this reason various fluorine containing nanocomposite coatings have been developed by sol-gel processing.The morphology of these hydrophobic surfaces has been controlled by varying the content of silica particles regarding size, degree of aggregation, and concentration. The wettability is characterized by the measurement of dynamic contact angles against water. The complete range of different wettability regimes is accessible, i.e. smooth surfaces (both low advancing contact angle and hysteresis between advancing and receding contact angle), surfaces within the Wenzel regime (high advancing contact angle and hysteresis), and superhydrophobic surfaces (high advancing contact angle and low hysteresis). The wettability is correlated with the surface roughness as determined using a profilometer or AFM.The wettability of superhydrophobic surfaces is greatly dependent on the surface tension of the liquid. By comparison of the tiltangle _t of a smooth and a superhydrophobic surface, a critical surface tension _c is identified, where _t (smooth surface) = _t (microstructured surface). The microstructured surface provides a better run-off of liquids _lg > _c 55 mN·m^–1.     

First experiments on transmutation studies of129I and237Np using relativistic protons of 3.7 GeV

First experiments on the transmutation of long-lived¹²⁹I and²³⁷Np using relativistic protons of 3.7 GeV are described. Relativistic protons generate in extended Pb-targets substancial neutron fluences. These neutrons get moderated in paraffin and are used for transmutation as follows:¹²⁹I(n,)¹³⁰I and²³⁷Np(n,)²³⁸Np. The isotopes¹³⁰I (T _1/2-12.36 h) and²³⁸Np (T _1/2=2.117 d) were identified radiochemically. One can estimate the transmutation cross-section (n,) in the given neutron field as (¹²⁹I(n,))=(10±2)b and (²³⁷Np(n,))=(140±30)b The experiments were carried out in November 1996 at the Synchrophasotron, LHE, Dubna, Russia. The investigation has been performed at the Laboratory of High Energies, JINR, Dubna.     

Crystal structure of the synthetic analog of radtkeite Hg<Subscript>3</Subscript>S<Subscript>2</Subscript>Cl<Subscript>1.00</Subscript>I<Subscript>1.00</Subscript>

The results of structural studies of the synthetic analog of the radtkeite mineral Hg₃S₂Cl_1.00I_1.00 are analyzed. The crystal structure of the compound has been refined; the unit cell parameters are a _m = 16.827(4) , b _m = 9.117(1) , c _m = 13.165(5) , = 130.17(2)°, V = 1543.3(8) ³, space group C2/m, Z = 8, R = 0.0527. A possible transition a ₀ = a _m; b ₀ = a _m + 2c _m; c ₀ = –b _m to the pseudo-orthorhombic F cell previously determined for radtkeite, where one of the angles ( ₀ ) is slightly different from 90° (89.55°), has been found. Each sulfur atom in the structure is bonded to three mercury atoms, forming SHg₃ umbrellas with distances 2.240(6) –2.474(8) and angles HgSHg 94.7(2)°–102.9(2)°. The SHg₃ fragments are linked through Hg vertices to form corrugated [Hg₁₂S₈] layers. The halogen atoms lie inside and between the [Hg₁₂S₈] layers; the distances are Hg-Cl and Hg-I 2.783(7) , 2.961(7) , and 3.083(4) –3.311(3) , respectively.Original Russian Text Copyright © 2004 by N. V. Pervukhina, S. V. Borisov, S. A. Magarill, D. Yu. Naumov, V. I. Vasiliev, and B. G. NenashevTranslated from Zhurnal Strukturnoi Khimii, Vol. 45, No. 4, pp. 755–758, July–August, 2004.This revised version was published online in April 2005 with a corrected cover date.     

Crystal and Molecular Structure of 5,7,12,14-Tetramethyl-1,4,8,11-tetraaza-4,6,11,13-tetraenatogold(III) Bromide [Au(C14H22N4)]Br

The crystal and molecular structure of [Au(C₁₄H₂₂N₄)]Br has been determined. Monoclinic crystals, a=12.592(2), b=6.309(1), c=19.628(2) ; =98.00(1)°, V=1544.1(4) ³, Z=4, d_calc=2.251 g/cm³, space group C2/c. The structure consists of virtually planar centrosymmetric [Au(C₁₄H₂₂N₄)]⁺ cations and Br^- anions. The coordination sphere of the gold atom involves four nitrogen atoms of the ligands, forming a planar square. The Au–N bond lengths are equal (the mean length is 1.982(7) ). The C–C and C–N bonds inside the -diiminate rings are delocalized. The parameters of the -diiminate rings of the [Au(C₁₄H₂₂N₄)]⁺ cation are compared with the parameters of the related complexes.     

Triterpene Glycosides of Astragalus and Their Genins. LXI. Occurrence of Cycloartane 6-O-Monodesmosides

Cyclosiversigenin 6-O--L-rhamnopyranoside and 6-O--D-glucopyranoside were isolated fromAstragalus coluteocarpusBoiss. (Leguminosae) andAstragalus dissectusB. Fedtsch. et N. Ivanova, respectively. Cyclosiversigenin 5-O--L-rhamnopyranoside was shown to be an artifact forAstragalus coluteocarpus.Thus, the cyclosiversigenin 6-O--D-glucopyranoside that was isolated from certainAstragalusspecies is hypothesized also to be an artifact. Glycosylation of the 6 -hydroxyl group of cycloartanes by D-glucose and D-xylose, in contrast with other substituents, does not change the low-field position of the PMR signal of the 4-CH ₃ group (1.65 2.01 ppm) that is caused by the influence of deuteropyridine directly on the 6 -hydroxyl. Obviously one of the hydroxyls of the -D-glucopyranoside or -D-xylopyranoside residues has the same effect in this instance.     

Theoretical models of calorimetric systems

In the present paper the dynamic properties of nonisothermal-nonadiabatic calorimeters have been analysed. In these calorimeters the thermal effect produced is partly accumulated in the calorimetric vessel, and partly transmitted to the shield with constant temperature. The generalized equation of the heat balance and the equation of the dynamics have been given for this type of calorimeter. The dependence between the course of the thermal effectQ in timet as a function of the temperature changes of the calorimeter has been presented. DependencesQ(t)=f[(t)] for a calorimeter with different domain configurations distinguished in it, and with different mutual locations of heat sources and temperature sensor have been given. Practical application of the considerations presented has been given.

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Zusammenfassung Die Eigenschaften der sog. nicht-isotherm-nicht-adiabatischen Kalorimeter werden analysiert. In diesen Kalorimetern wird der ausgelöste thermische Effekt teils im Kalorimetergefäß gespeichert und teils dem Konstanttemperaturschild übertragen. Die verallgemeinerte Gleichung des Wärmegleichgewichts und die Gleichung der Dynamik werden für diesen Kalorimetertyp mitgeteilt. Die Abhängigkeit zwischen dem Verlaufe des thermischen EffektesQ in der Zeitt als Funktion der Temperaturänderungen des Kalorimeters werden ebenfalls mitgeteilt. Die AbhängigkeitenQ(t)=f[(t)] werden für ein Kalorimeter mit verschiedenen Bereichskonfigurationen, verschiedenen gegenseitigen Störungen der Wärmequelle und des Temperatursensors angegeben. Es wird auch die praktische Anwendung der beschriebenen Anordnungen gezeigt.

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Résumé Les propriétés dynamiques des calorimètres appelés non-isothermes/non-adiabatiques sont examinées dans cet article. Dans ces calorimètres, l'effet thermique étudié est, en partie, accumulée dans la cellule calorimétrique et, en partie, transmis à la gaine à température constante. On donne l'équation générale du bilan thermique et l'équation de la thermocinetique pour ce type de calorimètre. L'évolution de l'effet thermiqueQ pendant le tempst est exprimée en fonction des variations de température du calorimètre en tempst. Les relationsQ(t)=f[(t)] sont données pour un calorimètre avec différentes configurations et différentes altérations mutuelles des sources de chaleur et des détecteurs de température. On donne également une application pratique des considérations présentées.

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- . , . . Q t . Q(t)=f[(t)] . .

     

Kinetic analysis of temperature-programmed desorption of hydrogen after reduction of a NiNaY zeolite

From the kinetic analysis of TPD curves it can be calculated that hydrogen desorption after reduction at lower temperatures can be described by a rate equation of first order, while reduction at higher temperatures provides a second order equation interpreted by a change of the rate-determining step of the complex desorption process.

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, , , 2- . , .

     

State of components in contact solutions based on Pd(II) salts and Fe(NO3)3 for ethylene oxidation to EGMA

Physico-chemical studies of contact solutions based on Pd(II) salts and Fe(NO₃)₃ for ethylene oxidation to EGMA have been carried out.

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- (II) .

     

Radical scavenging properties of a flavouring agent–Vanillin

Using pulse radiolysis technique, the one-electron oxidation of vanillin (V-OH) with azide radicals, at pH 6 and 9 resulted in the formation of vanillin phenoxyl radical with k = 6.7 × 10⁷ and 2.5 × 10⁹ dm³ mol^-1 s^-1, respectively. The transient absorption spectra of the vanillin phenoxyl radical (V-O) formed either at pH 6 or 9, showed a _max at 410 nm. At pH 5, the OH radicals seem to form an adduct with vanillin, _max at 430 nm and k(OH + V-OH) = 3.3 × 10⁹ dm³ mol^-1 s^-1, while at pH 9, the OH radical reaction resulted in the formation of vanillin phenoxyl radical with _max at 410 nm and k(OH + V-O-) = 6.6 × 10⁹ dm³ mol^-1 s^-1. The reactivity of NO₂radicals with vanillin is lower by orders of magnitude signifying an incomplete reaction. In general, the rate constants for the reaction of OH, N, NO radicals with vanillin were higher at pH 9 than at the lower pH. Its reactivity with other one-electron oxidants like CCl₃OO, CHCl₂OO and CH radicals and the ability to chemically repair tryptophanyl and guanosyl radicals with k = 1.5 - 4 × 10⁷ dm³ mol^-1 s^-1 indicate its antioxidative behaviour.     

Reactivity of coordinated O2? towards. One-electron oxidants

Ion-radical complexes Ti(IV) (O ₂ ^– ) are unreactive towards most oxidants except Ce(IV) and Cr₂O ₇ ^2– . The one-electron redox potential for the O_{2 coord.}/O _{2 coord.} ^– couple lies between 1 and 1.6 V.

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- O ₂ ^– Ti(IV) , Ce(IV) Cr₂ O ₇ ^2– . - O_{2 .}/O ₂ ^– . 1 1,6 .

     

The structure and harmonic vibrational frequencies of the weakly bound complexes formed by HF with CO,CO2 and N2O

The structure and harmonic vibrational frequencies of several weakly bound complexes formed by HF are reported. Theab initio MP2 approach is used with large basis sets for the optimisation of geometries and the determination of harmonic frequencies. COHF and OCHF are examined; both are found to be minima, with the latter being the dominant structure. The linear OCOHF andT shaped OCOFH are studied, but only the linear structure is a minimum. N₂OHF has two minima on the surface corresponding to bent NNOHF and linear ONNHF structures.     

Crystallite size effect of Pd/charcoal catalysts for benzene hydrogenation

The dispersity, calculated from the particle size distribution functions obtained by Small Angle X-ray Scattering (SAXS) measurements, when related to the chemical behavior of Pd/charcoal catalysts in benzene hydrogenation, points out that this reaction is mildly structure-sensitive below the range of 40 Å, whereas no dependence on particle size is observed above this limit.

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, , (SAXS), Pd/ , , 40 Å .

     

Two-electron atomic wave functions which satisfy proportionality relations between one-and two-electron moments

Based on momentum- and position-space analyses of the moment operators for two-electron atoms, it is shown that there exists a family of two-electron wave functions which satisfy a proportionality relation, r/ ₁ ^v /r ₁₂ ^v =p/ ₁ ^v /p ₁₂ ^v =2^–v/2, between the one and two-electron moments in position and momentum spaces, where v is an arbitrary number for which the moments are well-defined.     

Thermodynamic properties of liquids,including solutions

Summary A new theoretical treatment of the dependence of surface pressure on the concentration of linear polymer molecules in a monolayer is presented. The development follows closely that in the author's new theory of the thermodynamic properties of three-dimensional solutions.

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Zusammenfassung Es wird eine neuartige theoretische Untersuchung vorgelegt über die Abhängigkeit des Oberflächendruckes von der Konzentration an linearen Makromolekülen in einer monomolekularen Schicht. Die Entwicklung schließt sich eng an des Autors neue Theorie der dynamischen Eigenschaften von dreidimensionalen Lösungen an.

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Glossary A Area of the monolayer surface - B ₁,B ₂ Functions in the expansion of in powers ofm/A. See [38] - E Intermolecular energy in the monolayer. See [2]. It is negative for attraction energy - G Gibbs energy. See [1] - H Enthalpy. See [1] - K Equilibrium constant, defined by [3]. Equal to 1 for perfect randomness of segment contacts - K A constant, related toK by [8] - M ₁,M ₂ Molar masses (molecular weights) of substrate and polymer - N _a Avogadros number=6.0225×10²³ mol^–1 - R Molar gas constant=8.3143 JK^–1 mol^–1 - S Entropy. See [1] - S _cc Correction to the combinatorial entropy to allow for imperfect randomness - S _or Contribution to the entropy of mixing to allow for concentration dependence of entropy of orientation, vibration and rotation of molecules and segments - S _rm Combinatorial entropy of mixing, assuming perfect randomness - T Temperature in kelvins - a ₀ ,a ₀ Areas in monolayer occupied by one mole (Avogadros number) of solvent and polymer segments, respectively. See [10] - g _K A function ofK and the concentration, defined by [7] - m Mass of polymer in the monolayer - m/A Mass/area ratio. Related to area fractions by [14] - n Average number of segments per polymer molecule - r _a =a ₀ /a ₀ Segment area ratio. See [16] - r = ₀ / ₀ Contacting segment outline ratio. See [16] - r _a/ =r _a /r See [16] - r _/a =r /r _a See [16] - x ₁,x ₂ Mole fractions of solvent and polymer in the monolayer - z ,z Contacting segment outline fractions, defined by [9] - Surface pressure required to keep monolayer in areaA - , Designating solvent and polymer segments, respectively - , , Energy per unit length of contact between pairs of segments of the type indicated. See [6] - Energy change when two unit lengths of contacts between like segments are replaced by two unit lengths of contacts between unlike segments. Defined by [6] - Energy parameter, defined by [5] - ₁, ₂ Densities of the pure components (mass/volume) - _m Surface density of polymer in a completely filled monolayer (mass/area) - , Sum of the contacting outlines, for segments of the type indicated, in the monolayer - ⁰ , ⁰ Average contacting outline per segment, of the type indicated - , , Sum of the contact lengths, for contacts of the type indicated, in the monolayer - ₁, ₂ Area fractions, measuring the fractions of the monolayer area occupied by solvent and polymer molecules, respectively.     

μSr studies of free radicals in the gas phase

Muonium (Mu=₊+e^-) is the bound state of a positive muon and an electron. Since the positive muon has a mass about 1/9 of the proton, Mu can be regarded as an ultra light isotope of hydrogen with unusually large mass ratios (MuHDT=1/9123). The muon spin rotation technique (SR) relies on the facts that (1) the muon produced in pion decay, ^{+ +} + , is 100% spin polarized and (2) the positron from muon decay is emitted preferentially along the instantaneous muon spin direction at the time of the muon decay.In transverse field SR (TF-SR), the precession of the muon spin in muonium substituted radicals is directly observed by detecting decay positrons time differentially. From observed radical frequencies, the hyperfine coupling constants (A ) of C₂H₄Mu, C₂D₄Mu,¹³C₂H₄Mu, C₂F₄Mu, and C₂H₃FMu are determined. In the longitudinal field avoided level crossing (LF-ALC) technique, one observes the resonant loss of the muon spin polarization caused by the crossing of hyperfine levels at particular magnetic fields. The LF-ALC method together with the information onA obtained from TF-SR allows one to determine the magnitude and sign of the nuclear hyperfine constants at - and -positions. Results are compared with hydrogen substituted ethyl-radicals and isotope effects are discussed.