The electronic structure of molecules by a many-body approach

The vertical valence ionization potentials of cyclopropane, ethylene oxide and ethylene imine are calculated by a many-body Green's function method. For C₃H₆ the ordering of the ionization potentials is 2e(), 1e(), 2a₁(), 1a₂(), 1e(). The assignment of the 2a₁ and the 1a₂ ionization potentials which has been controversial is thus clarified. The ordering is in agreement with the result obtained via Koopmans' theorem. For ethylene oxide and ethylene imine Koopmans' theorem fails in predicting the correct order of ionic states. For C₂H₄O the ordering of the ionization potentials is 2b ₁(), 4a ₁, 1a ₂(), 2b ₂,3a ₁, 1b ₁(), 1b ₂, 2a ₁ and for C₂H₅N 6a, 5a, 3a, 2a, 4a, 3a, 1a, 2a. The agreement of the computed ionization potentials with the experimental values is very satisfactory.     

Crystal and molecular structure of a crown-bridgedp-t-butyl-calix[4]arene (1:1) pyridine complex. Host-guest interaction model based on molecular mechanics analysis [1]

The crystal and molecular structure of a crownedp-t-butyl-calix[4]arene (1:1) pyridine complex is reported. Colourless transparent prismatic crystals (obtained from pyridine) C₅₄H₇₄O₈·C₅H₅N,a=13.486(4),b=15.193(4),c=16.432(5) Å, =116.44(4)°, space groupP2₁,Z=2,D _calc=1.02g cm^–3, CuK radiation =1.5418 Å (CuK )=4.99 cm^–1. Refinement was carried out using 1702 reflections withI>3(I) toR 0.12. The macrocycle shows a distorted cone conformation which defines an intramolecular apolar cavity whose elliptical aperture is 11.5×8.6 Å calculated as distances between the two opposite central C atoms of the Bu ^t groups. A molecule of pyridine is included in this cavity, whereas the intermolecular cavities of the host lattice remain empty. The influence of the guest molecule on the conformation of the calixarene-crown is discussed. Potential energy calculations are performed in order to understand the nature of the host-guest interactions responsible for the stabilisation of the complex. Evidence for stabilizing CH₃- interactions are obtained from the calculations. Supplementary Data relevant to this article have been deposited with the British Library as supplementary Publication No. SUP 82068 (9 pages).     

Clusters of hydrogen molecules: Ab initio SCF calculations corrected semiempirically for correlation energies

Stabilization energy of the (H₂) _n clusters (n = 2–8) was calculated as a sum of the SCF interaction energy and the semiempirical interaction correlation energy estimated according to Sinanolu and Pamuk. Optimum successive attachment of hydrogen molecules leads to the formation of a gas-phase solvation shell consisting of seven hydrogen molecules. Basis set effect has been found to be important with all clusters under study. The non-additivity effect was investigated with the (H₂)₄ cluster. Vertical ionization potentials of the clusters considered are predicted to be 0.4–0.6 eV lower than the ionization potential of the parent H₂ molecule.     

Synthesis and X-Ray Crystal Structure Study of ]2-Methyl-4-(2-methylbenzoyl)-phenoxy] Acetic Acid Hydrazide

Benzophenone analog 3 has been synthesized and characterized by the X-ray diffraction (XRD) method. The compound crystallizes in a monoclinic space group P2₁/c with cell parameters a = 7.701(8) Å, b = 7.151(5) Å, c= 28.323(3) Å, = 104.639(4)°, Z = 4. The structure exhibits intra- and intermolecular hydrogen bonding of the type N–HO, C–HO, and N–HN. The molecules are interlinked through hydrogen bonds forming an infinite chain. This polymeric-like structure may play an important role in biological activity.     

Cyclodextrin-accelerated oxidation of iodide by oxygen in aqueous solutions containing HClO4

The oxidation of iodide to I ₃ ^– by oxygen dissolved in water containing HClO₄ has been found to be accelerated by -cyclodextrin (-CD). Among -, -, and -CDs, -CD is the most effective mediator for the oxidation reaction of iodide by oxygen. The oxidation rate of iodide is first order in the concentrations of -CD and HClO₄, whereas it is second order in the KI concentration.Part of this work was carried out at Department of Physics, Miyazaki Medical College, Miyazaki 889-16, Japan.     

An Inorganic-Organic Hybrid Supramolecular Hydrogen-Bonding and π-π Stacking Network Containing Ge4S4− 10 Cluster: Synthesis and Characterization of (H2bipy)2Ge4S10⋅(bipy)⋅7H2O (bipy=4,4′-bipy)

The reactions of TMA₄Ge₄S₁₀ (TMA=tetramethylammonium), Cu(NO₃)₂3H₂Oand 4,4-bipy under hydrothermal environment result in the formation of (H₂bipy)₂Ge₄S₁₀(bipy)7H₂O (1), which has been structurally characterized by single crystal X-ray analysis. The 3-D structure of 1 can be viewed as an inorganic-organic hybrid supramolecular hydrogen-bonding (hydrogen bonds: O–HO, N–HN, C–HO, N–HO, and O–HS) and - stacking network containing Ge₄S^4– ₁₀ clusters and novel [H₂bipybipyH₂bipy] trimers.     

Aqueous Solution Inclusion of the Nonionic Surfactant C 12 E 4 in β-Cyclodextrin: Implications of Micellization in Stoichiometry Determination and Model Calculations

The inclusion of -n-dodecyl--hydroxytetra(oxyethylene), C₁₂E₄, in -cyclodextrin (CD) has been studied in aqueous solution. Guest encapsulation is recognized by the upfield variations in the chemical shifts of the H3 and H5 inner protons of CD, and the chemical shift differences of the H5 protons are used for determining the complex stoichiometry (2CD : 1C₁₂E₄) by the continuous variation method. Self-association (micellization) of the surfactant molecules is considered, and the relative amount of surfactant involved in micellar systems at the stoichiometric point estimated. A two-layered integrated molecular orbital and molecular mechanics approach with the PM3 and UFF model chemistries for the guest and host, respectively, was used to perform full geometry optimizations and frequency calculations on the host-guest systems. Energies for the optimized structures were subsequently obtained by single point calculations at the Hartree–Fock level using the STO-3G basis set. These calculations showed that one C₁₂E₄ molecule encapsulated by a head-to-head CD dimer is a stable model system in consonance with the experimentally determined stoichiometry, and that the 1 : 1 complex is not stable with respect to dissociation. In the stable 2 : 1 model system, the guest molecule is appreciably tilted with respect to the CD dimer axis and presents a gradually bent alkylic chain in clear manifestation of conformational flexibility. Model calculations for CD inclusion complexes of other oligo(oxyethylene) molecules further indicate that the number and strength of HH intermolecular close contacts reflect the position and conformational flexibility of the guest hydrophobic chain inside CD.     

Hardness and phase analysis of IN 718 deformed at high strain rate

Specimens of the nickel base alloy IN 718 deformed at high strain rate (~10 s^–1), as realized in a screw press, have higher strength than parts forged conventionally in a hydraulic press. Microstructure analyses in light and transmission electron microscopes reveal the precipitation of very small Ni₃Nb particles (-phase) to be the reason for the increased hardness. Several processing routes are discussed and analyzed in relation to the TTT-diagram of IN 718.     

Diffraction and XPS studies of Cu complexes of intercalated compounds of α-zirconium phosphate. I: Derivation of structural models from powder diffraction data

Reasonable structural models are proposed for the Cu complexes of two intercalated compounds of -Zr(HPO₄)₂·H₂O (-ZrP): one with 1,10-phenanthroline (A) and the other with 2,2-bipyridyl (B). The models are derived from considerations of the unit-cell geometry changes undergone by -ZrP upon insertion of, first, the organic molecules and then copper, in accordance with a set of general criteria of structural analysis called the comparison method.     

Kinetics of oxidation of glycine and valine by chloramine-T in hydrochloric acid medium

The kinetics of oxidation of glycine and valine by chloramine-T in hydrochloric acid medium has been studied. The rate of disappearance of chloramine-T shows a first order dependence on both chloramine-T and the amino acid, and an inverse first order with respect to [H⁺]. The solvent isotope effect was studied using heavy water. The kinetic parameters,E _a ,Arrhenius factorA, H and S and G have been calculated. A rate law in agreement with experimental results has been derived. A mechanism is proposed.

---

Über die Kinetik der Oxidation von Glycin und Valin mit Chloramin-T in salzsaurem Medium

Zusammenfassung Die Kinetik der Oxidation von Glycin und Valin mit Chloramin-T in Salzsäure wurde untersucht. Die Geschwindigkeitskonstante des Wegreagierens von Chloramin-T zeigt eine Abhängigkeit erster Ordnung sowohl von Chloramin-T als auch von der Aminosäure und ist invers erster Ordnung bezüglich [H⁺]. Der Lösungsmittel-Isotopeneffekt wurde mit D₂O untersucht. Es wurden die kinetischen Parameter,E _a , derArrhenius-FaktorA, H , S und G , bestimmt. Ein Mechanismus, der in Übereinstimmung mit den experimentenllen Daten ist, wird vorgeschlagen.

     

Synthesis of new pyridazino[4′,3′:4,5]-thieno[3,2-d]-1,2,3-triazine and pyrimido[4′,5′:4,5]thieno[2,3-c]pyridazine derivatives

Summary 8,9-Diphenylpyridazino[4,3:4,5]thieno[3,2-d]-1,2,3-triazin-4(3H)-one (2), 3-substituted 8,9-diphenylpyridazino[4,3:4,5]thieno[3,2-d]-1,2,3-triazin-4(3H)-ones (3a–c), 3,4-diphenylpyrimido[4,5:4,5]thieno[2,3-c]pyridazin-8(7H)-one (4), 8-chloro-3,4-diphenylpyrimido[4,5:4,5]thieno[2,3-c]pyridazine (5), 8-substituted 3,4-diphenylpyrimido[4,5:4,5]thieno[2,3-c]pyridazines (6a–h) and 7-substituted 3,4-diphenylpyrimido[4,5:4,5]thieno[2,3-c]pyridazin-8(7H)-ones(7a–c) were synthesized from 5-amino-3,4-diphenylthieno[2,3-c]pyridazine-6-carboxamide (1).

---

Synthese neuer Pyridazino[4,3:4,5]thieno[3,2-d]-1,2,3-triazin-und Pyrimido[4,5:4,5]thieno[2,3-c]pyridazin-Derivate

Zusammenfassung Folgende Verbindungen wurden ausgehend von 5-Amino-3,4-diphenylthieno[2,3-c]pyridazin-6-carboxamid (1) synthetisiert: 8,9-Diphenylpyridazino[4,3:4,5]thieno[3,2-d]-1,2,3-triazin-4(3H)-on (2), 3-substituierte 8,9-Diphenylpyridazino[4,3:4,5]thieno[3,2-d]-1,2,3-triazin-4(3H)-one (3a–c), 3,4-Diphenylpyrimido[4,5:4,5]thieno[2,3-c]pyridazin-8[7H]-on (4), 8-Chlor-3,4-diphenylpyrimido[4,5:4,5]thieno[2,3-c]pyridazin (5), 8-substituierte 3,4-Diphenylpyrimido[4,5:4,5]thieno[2,3-c]pyridazine (6a–h) und 7-substituierte 3,4-Diphenylpyrimido[4,5:4,5]thieno[2,3-c]pyridazin-8(7H)-one (7a–c).

     

Electronic structure and OK α spectra of carbonyl-containing pentafluorobenzene derivatives

The OK spectra have been obtained for several pentafluorobenzene derivatives, using acetone as a reference molecule. The MNDO calculations have been performed for all the compounds under study, and simulated spectra have been plotted. The -interaction between the carbonyl group and the pentafluorophenyl ring has been shown to occur mostly in the system of inner molecular orbitals.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 314–318, February, 1993.     

Synthesis of some 5′-O-amino acid derivatives of uridine as potential inhibitors ofUDP-glucuronosyltransferase

Summary In an attempt to develop potential inhibitors ofUDP-glucuronosyltransferase, some 5-O-amino acid derivatives of uridine were synthesized. N-protectedL-amino acids were coupled at the 5-O-position of 2,3-O-isopropylideneuridine by esterification employing the method of symmetrical anhydrides in presence of 4-dimethylaminopyridine, 5-O-(N-benzyloxycarbonyl-O-tert.butyl-L-threonl)-23-O-isopropylideneuridine (1), 5-O-(N-tert.butyloxycarbonyl-O-benzyl-L-seryl)-2,3-O-isopropylideneuridine and (2), 5-O-(N-tert.butyloxycarbonyl-L-valyl)-2,3-O-isopropylideneuridine (3), and 5-O-(N-tert.butyloxycarbonyl-L-valyl)-2,3-O-isopropylideneuridine (4) were obtained in good yield after column chromatography on silica gel. The treatment of2 withTFA/CH₂Cl₂ (6:1) at room temperature for 30 min led to a selective removal of theBoc group without deblocking of the 2,3-O-isopropylidene group of uridine. Treatment of2 withTFA/H₂O (5:1) at room temperature for 1 h, however, released bothBoc and 2,3-isopropylidene groups. TheZ group of1 was deprotected by catalytic hydrogenolysis over 10% Pd/C/ammonium formate.

---

Synthese von 5-O-Aminosäurederivaten des Uridins als potentielle Inhibitoren derUDP-Glukuronosyl-Transferase

Zusammenfassung In einem Versuch, potentielle Inhibitoren derUDP-Glukuronosyl-Transferase zu entwickeln, wurden einige 5-O-Aminosäurederivate des Uridins synthetisiert. N-GeschützteL-Aminosäuren wurden durch Veresterung mit der 5-O-Position des 2,3-isopropylidenuridins gekuppelt (Methode der symmetrischen Anhydride in der Gegenwart von 5-Dimethylaminopyridin). Solcherweise wurden 5-O-(N-Benzyloxycarbonyl-O-tert.butyl-L-threonly)-2,3-O-isopropylidenuridin (1), 5-O-(N-tert.Butyloxycarbonyl-O-benzyl-L-seryl)-2,3-O-isopropylidenuridin (2), 5-O-(N-tert.Butyloxycarbonyl-L-leucyl)-2,3-O-isopropylidenuridin (3) und 5-O-(N-tert.Butyloxycarbonyl-L-valyl)-2,3-O-isopropylidenuridine (4) nach Säulenchromatographie (Kieselgel) in guter Ausbeute hergestellt. Die Behandlung von2 mitTFA/CH₂Cl₂ (6:1) bei Zimmertemperatur (30 min) führte zu einer selektiven Abspaltung derBoc-Gruppe ohne Deblockierung der 2,3-O-Isopropylidengruppe des Uridins. Eine Behandlung von2 mitTFA/H₂O (5:1) bei Zimmertemperatur für 1 Stunde führte hingegen zur Abspaltung sowohl derBoc als auch der 2,3-O-Isopropylidengruppe. DieZ-Gruppe von1 wurde durch katalytische Hydrogenolyse auf 10% Pd/C/Ammoniumformiat abgespalten.

     

Chain entanglement,mechanical properties and drawability of poly(lactide)

The observed brittle fracture behavior of amorphous polylactides seems to be contradicted by the low value ofC =2 determined for poly(L-lactide) by Flory and coworkers. Such very flexible polymer chains deform by shear yielding, and fracture in a ductile manner. In this study,C was estimated in a number of ways, resulting in much higher values ofC =11.7 andC =9.1 for poly(L-lactide) and L- and D-lactide copolymers, respectively. These high values ofC and the low entanglement density account for the brittle fracture behavior of amorphous poly(lactide), as well as for the maximum attainable draw ratios of poly(L-lactide) networks and melt spun fibers. Bulk polymerized poly(L-lactide) networks, where crystallization during polymerization impedes severe entangling, could be hot-drawn most effectively to draw ratios of 8–16, resulting in very strong materials with tensile strengths of 550–805 MPa. By comparison, amorphous, non-crystallizable L/D lactide networks, which do not crystallize during polymerization, could be drawn less, to =7. These materials with strengths up to 460 MPa could, nevertheless, be oriented much more effectively than linear, amorphous L/D lactide copolymers.     

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.     

SCF-CI studies on the electronic ground state of water: Potential energy hypersurface and spectroscopic constants

Large-scale Hartree-Fock self-consistent field calculations, employing extended Gaussian basis sets, and configuration interaction studies are performed to calculate the energy hypersurface of the electronic ground state of the water molecule and to investigate the accuracy requirements in view of the determination of molecular spectroscopic constants. From the calculated points on the hypersurface the theoretical equilibrium geometry, the force field through fourth order, the spectroscopic constants _i, x_ij, _i as well as the Darling-Dennison and Fermi resonance constants are evaluated. The CI surface yields an equilibrium structure for H₂O withr _e = 0.9501 Å and _e=105.33 ° (r _exp = 0.9572 Å and _exp = 104.52 °). The vibrational levels are obtained with a systematic error of about 2 percent and the rotational constants to about 1 percent compared to spectroscopic data. The relative energy maximum corresponding to the linear structure with = is calculated to be 11890cm^–1, within the error limits of the values deduced from experimental measurements.     

Solvent/water partitioning of dimethylmethylphosphonate (DMMP) as a probe of solvent acidity

Experimentally determined partition coefficients for DMMP between NaCl-saturated water and 20 solvents were correlated using the solvatochromic parameters , , and ^*. An inverted LSER was then used to predict for 7 additional solvents. The new cohesion parameters and ^*2 were found to be more representative of cavity formation than _H ² . Most importantly, it was essential to include either or _H ² in the LSER. The partition method appears to be a useful adjunct to solvatochromic techniques in refining and extending the scale of solvent acidity and could be used to rationalize solvent selection in extraction processes.     

Studies on the γ-effects. Part 3. Variations in the γ-effects ofN-substituted benzylamines,o-aminomethylphenols and 3,4-dihydro-2H-1,3-benzoxazines against theE s ′ substituent constants

The magnitude of the -effects on¹³C chemical shifts was studied as function of theN-substitution [Me, Et, Bu, CH₂C₆H₅, CH₂CH₂C₆H₅, Prⁱ, Bu^t, Bu^s, c-C₆H₁₁, CH(CH₃)C₆H₅, Bu^t, or Ph] for several benzylamines,o-aminomethylphenols and 3,4-dihydro-2H-1,3-benzoxazines. A correlation between the _c-values and the steric substituent constants (E _s ) of theN-substituents proved useful in characterizing the variation of the -effects along with the conformational factors. The diastereospecificity of the -effects is discussed for purposes of configurational assignments.For part 2, see Ref. 1. This paper is also Part 5 in the series Studies on the Benzoxazine Series.     

Synthesis, Spectral and Structural Study of N-[1-(N,N,N′,N′-Tetramethylphosphoramidoyl)- 1H-Benzimidazol-2-yl]-Propionimidic Ethyl Ether

The preparation of N-[1-(N,N,N,N-tetramethylphosphoramidoyl)-1H-benzimidazol-2-yl]-proponimidic ethyl ester 2 has been achieved by the reaction of N-(1H-benzimidazol-2-yl)-proponimidic acid ethyl ester 1 with N,N,N,N-tetramethylchlorophosphoramide. The structure of compound 2 has been determined by X-ray diffraction. The results of (¹H, ¹³C, ³¹P) NMR, IR, EI-MS spectral data are consistent with those obtained from the X-ray diffraction. The compound crystallizes in the triclinic system, following the EsZ conformation. In the crystal, there are two weak C3–H3s1 and C15–H15sO1 intermolecular hydrogen bonds.