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51.
Blake AJ Brett MT Champness NR Khlobystov AN Long DL Wilson C Schröder M 《Chemical communications (Cambridge, England)》2001,(21):2258-2259
4,4'-Bipyridine N,N'-dioxide (L) acts as a hydrogen-bond acceptor in the compounds ([M(NO3)2(H2O)4].L2) (M = Co, Ni) to form doubly-interpenetrated framework materials with sixfold topological connectivity. 相似文献
52.
As supported PtxNi1–x catalysts are used for hydrogenation reactions, it seemed necessary to assess the surface composition of the reduced samples. To approach the usual reduction conditions we applied in situ reduction in a reaction chamber (1 mbar H2 up to 500 °C) placed in ultra high vacuum recipient (UHV: 10–9 to 2.10–10mbar). All ion scattering spectroscopy measurements were performed in UHV. Charging of the samples was avoided by electron bombardment (5 eV). The variation of the surface composition was determined after subsequent sputtering, thermal treatment at 500 °C and during oxygen adsorption. A comparison with previous results of surface compositions of binary alloys (polycrystalline foils [1, 2] and single crystals PtxNi1–x [3]) is given.Dedicated to Professor Dr. rer. nat. Dr. h. c. Hubertus Nickel on the occasion of his 65th birthday 相似文献
53.
54.
The hyperfine structure of the X2∑+, υ = 0 state of 88Sr35Cl has been investigated using microwave—optical polarization spectroscopy. Resolution of the hyperfine structure in transitions between low-lying rotational states has allowed the first determination of magnetic dipole and electric quadrupole coupling constants. The results are: b = 18.663(89) MHz, c = 7.72(30)MHz, and eqQ = 3.96(84) MHz. 相似文献
55.
Andreas Stockhammer Klaus-Hermann Dahmen Tobias Gerfin Luigi M. Venanzi Volker Gramlich Walter Fetter 《Helvetica chimica acta》1991,74(5):989-992
The cluster compounds [Pt3(μ-CO)3(PR3)3] act as Lewis bases towards the metal halides of Group XI, MX, Group XII, MX2, and Group XIII, MX3, to form cluster compounds of the composition [{MXn}{Pt3(μ-CO)3(PR3)3}]. The X-ray crystal structure, NMR and IR data are given for the compound [{ZnI}{Pt3(μ-CO)3(PPh(i-Pr)2)3}]. 相似文献
56.
The photolability of the antitumor antibiotic hedamycin ( 1 ) was investigated by irradiation in different solvents in the presence or in the absence of oxygen. The products formed were separated chromatographically and their structures determined by NMR spectroscopy. Photolysis of 1 in the presence of oxygen gave only one isolable product, photohedamycin A ( 3 ), where ring E of hedamycin had been transformed into an enol ether. The reaction in the absence of oxygen yielded the photohedamycins B, C, and D ( 5, 6 , and 7 , respectively). In these compounds, one of the epoxides of hedamycin had been opened reductively, and in photohedamycin D ( 7 ) the substituent at C(8) - originally ring E of hedamycin - was now acyclic. In addition to these compounds, the photolyses yielded a large number of unstable minor products, which could not be isolated. 相似文献
57.
Ernst M Detken A Böckmann A Meier BH 《Journal of the American Chemical Society》2003,125(51):15807-15810
Proteins are not always available in amounts desirable for solid-state magic-angle spinning (MAS) nuclear-magnetic resonance (NMR) spectroscopy. To maximize the signal-to-noise ratio achievable with small samples, the filling factor must be optimized by using small-diameter MAS rotors. These rotors have the added benefit of allowing higher radio frequency field amplitudes during polarization transfer steps and during decoupling periods as well as allowing higher spinning frequencies. We demonstrate the advantages of relatively fast MAS (30 kHz using a 2.5 mm rotor) compared to MAS at 12 kHz for the 10.4 kDa model protein Crh with 93 residues and show that the signal-to-noise ratio in two-dimensional correlation spectra can be significantly improved by taking advantage of optimized pulse sequences available with rapid MAS. 相似文献
58.
Siavosh Mahboobi Andreas Sellmer Thomas Burgemeister Alexei Lyssenko Dieter Schollmeyer 《Monatshefte für Chemie / Chemical Monthly》2004,135(3):333-342
The synthesis of the naturally occurring and biologically active alkaloids 1 and 2, first isolated from the red ascidian Botryllus leachi by Duran et al. [1], is described and the structure proposed for Botryllazine B (1) is confirmed. The analytical data for 2-(p-hydroxybenzoyl)-4-(p-hydroxyphenyl)imidazole (2) are discussed and compared with the literature. With special emphasis of 1H NMR data the tautomerism of aroylimidazolemethanones is described. 相似文献
59.
Schiefer M Reddy ND Ahn HJ Stasch A Roesky HW Schlicker AC Schmidt HG Noltemeyer M Vidovic D 《Inorganic chemistry》2003,42(16):4970-4976
The syntheses of the ionic compounds [Li(+).2 dioxane (2,6-iPr(2)C(6)H(3)N(SiMe(3))Al(C triplebond CSiMe(3))(3))(-)].0.75 dioxane (1), [(Li(+))(2).(dioxane)(7)](0.5) [2,6-iPr(2)C(6)H(3)N(SiMe(3))Ga(C triplebond CSiMe(3))(3)(-)].1.5 dioxane (2), and [(Li(+))(2).(dioxane)(7)](0.5) [2,6-iPr(2)C(6)H(3)N(SiMe(3))In(C triplebond CSiMe(3))(3)(-)].1.5 dioxane (3) by the reaction of the corresponding organo metal chloride with LiC triplebond CSiMe(3) are reported. The neutral ethynyl compounds Br-Al(C triplebond CtBu)(2).2 THF (4), Cl-Ga(C triplebond CtBu)(2).THF (5), Cl-In(C triplebond CtBu)(2).2 THF (6), Al(C triplebond CtBu)(3).C[N(Me)CMe](2) (7), Ga(C triplebond CtBu)(3).dioxane (8), and In(C triplebond CtBu)(3).NEt(3) (9) have been obtained in good yields from the reaction of AlBr(3), GaCl(3), and InCl(3) with LiC triplebond CtBu in the presence of a Lewis base. Compound 7 is the first heterocyclic carbene substituted ethynyl derivative. Aluminum and gallium compounds with three terminal ethynyl groups Al(C triplebond CPh)(3).NMe(3) (10) and Ga(C triplebond CPh)(3).NMe(3) (11) have been prepared by the reaction of AlH(3).NMe(3) or GaH(3).NMe(3) with three equivalents of phenylethyne. All the above-mentioned compounds have been structurally studied. In compound 1 the lithium ion is coordinated to the three terminal ethynyl groups, whereas in compounds 2 and 3 the lithium is coordinated to the solvent (dioxane). Compound 8 crystallizes as a coordination polymer with dioxane molecules bridging the individual gallium units. 相似文献
60.
An application of automated on-line HPLC-HRGC is described for direct analysis of edible oils for migrated polymer additives. The sample preparation, separating the additive from the oil triglycerides, is carried out using normal phase HPLC. The fraction of the eluent containing the additive is automatically transferred to a HRGC where a second and final separation of the additive from minor oil components takes place. The method compares well with off-line separation methods. Migration data for Tinuvin 1577 from PET and PC polymers as well as an unspecified experimental polymer is given. The advantages and disadvantages of using different edible oils as food simulants are discussed. 相似文献