Studies on novel cyclodextrans: Inclusion of C60 and C70

Cycloisomalto-heptaose (CI-7) and cycloisomalto-octaose (CI-8) are two novel cyclodextrans. Treatment with C₆₀ or C₇₀ by kneading leads to the formation of four distinct water-soluble inclusion complexes: CI-7/C₆₀ (2: 1), CI-8/C₆₀ (2: 1), CI-7/C₇₀ (2: 1) and CI-8/C₇₀ (2: 1). Their formation and structures have been examined by UV vis spectroscopy, X-ray powder diffraction and fluorescence spectral studies. The reaction is a reversible process.     

Synthesis and In vitro biological activity of some 7-(5-aminomethyl-2-isoxazolidinyl)quinolone-3-carboxylic acids

The synthesis of the title compounds via nitrone cycloaddition is described. The in vitro antibacterial activity of these compounds is compared against 1-ethyl-6,8-difluoro-7-[3-[(ethylamino)methyl]-1-pyrrolidinyl]-1,4-dihydro-4-oxoquinoline-3-carboxylic acid (CI-934).     

Small-angle X-ray scattering from wet gels prepared from co-hydrolysis of tetraethoxysilane and vinyltriethoxysilane

Small-angle X-ray scattering was used to study the structure of wet gels prepared from co-hydrolysis of tetraethoxysilane (TEOS) and vinyltriethoxysilane (VTES) in the VTES/(VTES + TEOS) molar ratio ranging from 0 to 1. The wet gels at pH = 6 behave as a mass-fractal structure with characteristic size ξ and fractal dimension D, both increasing with the amount of VTES from ξ = 6.78 nm and D = 2.25 for pure TEOS until an almost homogenous structure with ξ ~ 24.9 nm and D ~ 2.85 is obtained for the wet gel prepared with pure VTES. The mass-fractal structures are built up by small primary clusters of characteristic size between ~0.35 and ~0.85 nm, the size increasing with the quantity of VTES. These small particles of the gels are formed by a restructuring process of a few larger macromolecules in the stable sols (pH = 2) on passing from the acid to the increased-pH step of the process.     

Hydrothermal synthesis, structure and quantum chemistry of transition metal complex supported by metal-oxo cluster [(Ni(phen)22 (ξ-Mo8O26)]

A nickel-1,10-phenanthroline complex supported on an octamolybdate, [(Ni(phen)_{2 2}(ξ-Mo₈O₂₆)], has been hydrothermally synthesized with MoO₃, H₂MoO₄, Ni(OAc)₂ 6H₃O and 1,10-phenathroline (1,10-phen) as raw materials. The crystals of the compound belong to monoclinic P2₁/n space group,a = 1.2952(2),b = 1.6659(10),c = 1.3956(12) nm, β =106.273(8)°,V = 2.8906(5) nm³,Z = 2. 5604 observable reflections (I >2σ(I)) were used for structure resolution and refinements to converge to finalR ₁ = 0.0414,wR ₂ = 0.0815. The result of structure determination shows that the compound contains octamolybdate possessing a novel structure type (named as ξ-isomer). The feature of ξ-[Mo₈O₂₆]^4- is that it is composed of Mo₆O₆ ring and two MoO₆ octahedral located at cap positions on opposite faces. The Mo₆O₆ ring contains two octahedral and four trigonal-bipyramidal Mo^VI atoms. Each ξ-[Mo₈O₂₆]^4- unit is bonded with two [Ni(phen)₂]²⁺ through terminal oxygen atoms of octahedral and neighbouring trigonal-bipyramidal Mo atom in the Mo₆O₆ ring. IR and UV-Vis spectra of the compound were measured and its electronic structure was studied by EHMO method.     

A Generalized Formula to Predict the Direction of an Equilibrium Shift

A generalized formula to predict the direction of an equilibrium shift, , is presented, where ξ is the extent of the reaction, t is the characteristic variable to affect an equilibrium and f is the characteristic function whose partial differential with respect to ξ can be used as an equilibrium criterion. When the stable equilibrium of a thermodynamic system is disturbed on condition that f exhibits a minimum with respect to ξ, the equilibrium will shift in the direction to resist the increase of f if the disturbance make f increase; however, the equilibrium will shift in the direction to accelerate the decrease of f if the disturbance make f decrease to minimize f. On condition that f exhibits a maximum with respect to ξ, the equilibrium will shift in the direction to resist the decrease of f if the disturbance make f decrease; however, the equilibrium will shift in the direction to accelerate the increase of f if the disturbance make f increase to maximize f. On the other hand, Le Chatalier’s Principle is not consistent with the real situations under certain circumstances     

Spectral moments of polymer graphs

Summary It is shown that for anyk, thekth spectral moment of a polymer graph composed ofn monomer units is an exact linear function of the parametern. This linear relation holds for all values ofn, greater than a critical value ₀=₀(k).on leave from Faculty of Science, University of Kragujevac     

Scaling Function Between the Exponential-6 and the Generalized Lennard-Jones Potential Functions

The van der Waals forces for non-bonded interaction can be expressed either by the Exponential-6 or by the Lennard-Jones(m-n) potential functions, whereby m > n. Hitherto a relationship exists between the Exponential-6 and the Lennard-Jones(12-6) potential functions, with a scaling factor = 13.772 at or near the equilibrium and = 12.0 for long range interaction. This paper attempts to develop relationships between Exponential-6 and a more generalized Lennard-Jones(m-n). Analysis reveals that the relationship exists only when n = 6 and that two sets of scaling factors (as functions of index m) applies for the relationship between Exponential-6 and the Lennard-Jones(m-6), whereby m > 6.     

Structures of new polar steroids from the Far-Eastern starfish <Emphasis Type="Italic">Ctenodiscus crispatus</Emphasis>

A fraction of sulfated polyhydroxylated steroids from the Far-Eastern starfish Ctenodiscus crispatus was investigated. The main component of this fraction was identified as (22E,24R,25R)-24-methyl-5α -cholest-22-en-3β,5,6β,15α,25,26-hexol 26-O-sulfate. For the compound stereoisomeric with respect to the side chain, the (24R,25S) or (24S,25R) relative configurations were assigned to the C(24) and C(25) chiral centers. The structures of two other compounds isolated from the fraction were identified as (22E, 24ξ)-26,27-bisnor-24-methyl-5α-cholest-22-en-3β,5,6β,15α,25-pentol 25-O-sulfate and (22E, 24ξ,25ξ)-24-methyl-5α-cholest-22-en-3β,5,6β,8,15α,25,26-heptol 26-O-sulfate. Dedicated to Academician N. K. Kochetkov on the occasion of his 90th birthday. __________ Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 1229–1234, May, 2005.     

Comparison Between a Generalized Electronic Diabatic Approach and the Born–Oppenheimer Separation Scheme in Inertial Frames

We discuss a generalized electronic diabatic (GED) approach to diagonalize the exact Hamiltonian of an n-electron system which embeds an external background of positive charges. This Hamiltonian, denoted by _e(q,), is defined in an inertial frame, and it contains a quantum part (the electrons with coordinates q) and a classical part (the external charges in a three-dimensional configuration ). We derive a GED basis set { _k (q)} using an operator _e(q,⁰) for a single configuration ⁰, and then show that these are also eigenfunctions for any other _e(q,); only the ordering of eigenvalues may depend on (i.e., k=k()). The GED functions can also be used to represent the eigenstates of a fully quantum-mechanical system of electrons and nuclei. We discuss briefly the differences between the present procedure and the standard Born–Oppenheimer (BO) technique in the clamped-nuclei approximation. As illustration, we show how chemical changes emerge as transitions among diabatic states mediated by an electromagnetic field.     

Ion Mobility Measurements of Nondenatured 12–150 kDa Proteins and Protein Multimers by Tandem Differential Mobility Analysis–Mass Spectrometry (DMA-MS)

The mobilities of electrosprayed proteins and protein multimers with molecular weights ranging from 12.4 kDa (cytochrome C monomers) to 154 kDa (nonspecific concanavalin A hexamers) were measured in dry air by a planar differential mobility analyzer (DMA) coupled to a time-of-flight mass spectrometer (TOF-MS). The DMA determines true mobility at atmospheric pressure, without perturbing ion structure from that delivered by the electrospray. A nondenaturing aqueous 20 mM triethylammonium formate buffer yields compact ions with low charge states, moderating polarization effects on ion mobility. Conversion of mobilities into cross-sections involves a reduction factor ξ for the actual mobility relative to that associated with elastic specular collisions with smooth surfaces. ξ is known to be 1.36 in air from Millikan’s oil drop experiments. A similar enhancement effect ascribed to atomic-scale surface roughness has been found in numerical simulations. Adopting Millikan’s value ξ = 1.36 and assuming a spherical geometry yields a gas-phase protein density ρ _p = 0.949 ± 0.053 g cm⁻³ for all our protein data. This is substantially higher than the 0.67 g cm⁻³ found in recent low-resolution DMA measurements of singly charged proteins. DMA-MS can distinguish nonspecific protein aggregates formed during the electrospray process from those formed preferentially in solution. The observed charge versus diameter relation is compatible with a protein charge reduction mechanism based on the evaporation of triethylammonium ions from electrosprayed drops.     

ξ-potential and surface dye-ability of poly(vinyl alcohol) fiber with different degree of formalization in a cationic dye solution

Summary The surface dyeability of the poly(vinyl alcohol) fiber with different degree of formalization was studied by measuring -potential of the fiber in alkaline aqueous solutions (pH 10) of a cationic dye Methylene Blue. With the increase in the dye concentration, the sign of the -potential of the fiber changed from negative to positive and thereafter the positive value approximated to saturated value, and the amount of dye adsorbed (expressed in mol/cm²-fiber) increased also. These results may possibly be attributed to the formation of the electrostatic bond between the fiber and the dye. The linear relations were found between and logC _d and its slope did not change with rise of temperature. The free energy of dyeing G (negative) calculated from the slope of the -logC _id curve, etc. increased with increasing the degree of formalization of the fiber. This fact corresponds to the increase in the surface dye adsorption with increasing the degree of formalization. With increasing the degree of formalization, the heat of dyeing H (negative) increased and the entropy of dyeing S (positive) decreased. The positive value of S for each fiber, suggests the formation of hydrophobic bond as a driving force to the dyeing of Methylene blue on the fiber surface in addition to the electrostatic bond.This paper is Part XXVII in a series on Studies on -potentials and Surface Dyeability of Natural and Synthetic Fibers in Dye Solution. Part XXVI: T. Suzawa andK. Kawakami, Nippon Kagaku Kaishi1975, No. 7,1134.     

Split series potential energy function

A split series potential energy function is developed herein such that it can be primarily reduced into generalized forms of Lennard-Jones, Morse, Buckingham, Linnett, and anything in between them by altering the type-parameters. Unlike the previous approach whereby the type-parameters act as weighting parameter between the inverse power and the exponential decay terms, the current approach attaches the type-parameters as indices to the denominator of every summation term. A change of the index shifts the series summation to mimic a curve that is representative of an inverse power, an exponential index, or a weighted proportion between the two. Comparison with the Lennard-Jones (12–6) and Exponential-6 (both ξ = 13.772 and ξ = 12) in the case of uncharged non-bonded interactions by using type-parameters (p, q) = (0, 0) and (p, q) = (1, 0) respectively in the model gives very good correlation. Comparison with the Morse potential in the case of bonded interaction by using (p, q) = (1, 1) gives excellent agreement. All results show that the use of only five expansion terms is sufficient for providing good agreement with the classical potentials. Better fit to experimental data and ab initio results are expected with the incorporation of coefficients in every term of the series expansion. The proposed model is useful for modeling the transition state from solid to fluid and vice versa.     

The electronic g-tensor of MgF: A comparison of ROHF and MRD?CI level results

Despite their importance in the characterization of molecular magnetism, electronic g-tensors have received rather little theoretical attention. In this work, however, the ground-state g-tensor of MgF is computed at both the ROHF and multireference CI levels. The calculations are expanded complete to second order in appropriate Breit-Pauli terms and the contributions of all important magnetically coupled excited states are accounted for. Both the CI- and ROHF-level Δg_∥-values (-59 and -55 ppm, respectively) are in agreement with experiment (-319 ± 500 ppm) within the range of experimental uncertainty. For Δg_⟂, however, the ROHF treatment yields a value (-659 ppm) in substantial disagreement with experiment (-1319 ± 500 ppm). Fortunately, this discrepancy is alleviated by CI level treatment (Δg_⟂ = -1447 ppm). © 1996 John Wiley & Sons, Inc.     

Synthesis of antimicrobial agents. II. Syntheses and antibacterial activities of optically active 7-(3-hydroxypyrrolidin-1-yl)quinolones

Two optically active isomers of 1-ethyl-6,8-difluoro-1,4-dihydro-7-(3-hydroxypyrrolidin-1-yl)-4-oxoquinoline-3-carboxylic acid ( 10 ) were prepared. One of the isomer, 7-[(3S)-hydroxypyrrolidin-1-yl] derivative 8 , was about 4 times more potent in vitro than the other, 7-[(3R)-hydroxypyrrolidin-1-yl] derivative 4 , and approximately two times more active than the racemate, 7-[(3RS)-hydroxypyrrolidine-1-yl] derivative 10. Optical active 8 was the most active in in vivo, followed by 10 , and 4 was the least active compound. But, they were more potent than CI-934 12 and norfloxacin. From the results, (3S)-hydroxypyrrolidinyl group was found to be one of the beneficial group for PCA-anti-bacterial agent.     

Thermal Properties of Polycrystalline ZnIn2Se4

A pulse method was used to measure the thermal conductivity, specific heat capacity C _p and thermal diffusivityξ of polycrystalline ZnIn₂Se₄ in the temperature range 300–600 K. The temperature dependence of λ, C _p and ξ demonstrated a light decrease for this material in the temperature range 300–600 K, indicating that there is not a significant change in the structure in this temperature range; this was confirmed by DTA measurements. The results showed that the mechanism of heat transfer is due mainly to phonons; the contributions of electrons and dipoles are very small. This revised version was published online in July 2006 with corrections to the Cover Date.     

An FTIR spectroscopic study of the kinetics and mechanism for the NO2-initiated oxidation of tetramethyl ethylene at 298 K

The kinetics and mechansim for the NO₂-initiated oxidation of tetramethyl ethylene (TME) have been studied using the FTIR spectroscopic method in mixtures containing NO₂ and TME (0.1?1.0 Torr) and N₂? O₂ (700 Torr) at 298 ± 2 K. While TME decayed according to -d[TME]/dt = k_obs[NO₂][TME], NO₂ exhibited a complex kinetic behavior. Furthermore, values of k_obs were dependent on [O₂]. Among the products were (CH₃)₂CO and at least three NO₂-containing compounds. These results indicate the formation of a nitro-alkylperoxy radical via reactions (1), (?1), and (2), and its subsequent reactions leading to the observed products. The [O₂]-dependence of k_obs yielded k₁ = (1.07 ± 0.15) × 10^?20 cm³ molecule^?1 S^?1 and k_?1/k₂ = (3.54 ± 0.61) × 10¹⁸ molecule cm^?3.     

Interaction between two similar plane parallel double layers for Mg<Subscript>3</Subscript>(PO<Subscript>4</Subscript>)<Subscript>2</Subscript> type asymmetric electrolytes at positive surface potential

The interaction between two similar plane double-layers for Mg₃(PO₄)₂ type asymmetric electrolytes was investigated with the aid of λ parameter method. The interaction energies for the system at positive surface potential were expanded in power series at low and high potential, respectively. The accurate numeral results and V′-ξ _d curves were given for y ₀ ≤ 20 and they can be used to check up the validity of approximate expressions obtained. When y ₀ ≥ 5, V′ hardly changes with y ₀. The interaction energies between two similar plane parallel double layers for symmetric and asymmetric electrolytes at y ₀ = 1 were compared; when ξ _d is small, the interaction energies for Mg₃(PO₄)₂ type electrolytes increase more drastically than for other type electrolytes. The present results are also fit for Al₂(SO₄)₃ type asymmetric electrolytes at negative surface potential. The article is published in the original.     

Electronic spectra and conformational states of mono- and diphenyl derivatives of [2.2]paracyclophane

Ultraviolet spectra of 4-phenyl-[2.2]paracyclophane and of the 4,7- and 4,13-diphenyl derivatives were interpreted. MINDO/3 total molecular energy andPPP—CI-1 energies of singlet transitions were calculated for different values of the dihedral angle of the phenyl ring with respect to the benzene ring of paracyclophane. Although most of the theoretical transitions correspond to local excitation within thePCP fragment, some of them result in a transfer of electron charge to the phenyl substituents.

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Elektronenspektren und Konformationen von Mono- und Diphenylderivaten des [2.2]Paracyclophans

Zusammenfassung Es werden die UV-Spektren von 4-Phenyl-[2.2]paracyclophan, 4,7- und 4,13-Diphenyl-[2.2]paracyclophan interpretiert. Für verschiedene Diederwinkel der Phenylringe relativ zu dem Benzolring des Paracyclophans wurden MINDO/3-Rechnungen für die Gesamtenergie undPPP—CI-1 Rechnungen für die Singlet-Übergänge durchgeführt. Die meisten der berechneten Übergänge gehören zu lokalen Anregungen innerhalb desPCP-Fragments, einige sind jedoch einem Elektronentransfer zu den Phenylsubstituenten zuzuschreiben.

     

Triterpene Glycosides from <Emphasis Type="Italic">Astragalus</Emphasis> and Their Genins. LXXI. Cycloorbicoside D,a New Glycoside from <Emphasis Type="Italic">Astragalus orbiculatus</Emphasis>

The new cycloartane glycoside cycloorbicoside D, which has the structure 23ξ,24ξ-cycloartan-3β6α,16β,23,24,25-hexaol 3-O-β-D-xylopyranoside, was isolated from the aerial part of Astragalus orbiculatus Ledeb. (Leguminosae). __________ Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 345–346, July–August, 2005.