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971.
Cs3[Tb10(C2)2]Cl21, A New Formula and Structure Type with Isolated Dimeric Clusters Cs3[Tb10(C2)2]Cl21 is obtained via the metallothermic reduction of TbCl3 with caesium in the presence of graphite as black single crystals. The crystal structure (monoclinic, C2/c, Z = 4; a = 2318.72(13); b = 1245.8(9); c = 1502.0(13) pm; β = 98.13(6)°; R = 0.089; Rw = 0.049) contains dimeric clusters that are built from two octahedra connected via one common edge and filled with C2 units. These isolated [Tb10(C2)2] clusters are surrounded by 26 chloride ligands which are then connected via i—a and a—a bridges in a way that voids for Cs+ of coordination number 10 are formed. 相似文献
972.
A novel transesterification reaction between acetylated maritime pine sapwood (Pinus pinaster Soland) and methyl benzoate (MB), in the presence of dibutyltin oxide (DBTO) as a catalyst, was performed. Reaction was confirmed by Fourier-transform infrared spectroscopy (FTIR) and 13C nuclear magnetic resonance cross-polarisation with magic-angle spinning (NMR CP MAS) analysis: signals corresponding to benzoylated wood were identified and, when transesterification was performed with ethyl trimethylsilylacetate (ETMSA), characteristic trimethylsilyl groups were detected. The acetyl/benzoyl exchange rate was found to increase with increasing amount of DBTO, temperature and reaction time and a concurrent deterioration of the woody material was evidenced. 相似文献
973.
Complete 1H and 13C NMR assignments of aurasperone A and fonsecinone A, two bis-naphthopyrones produced by Aspergillus aculeatus 总被引:1,自引:0,他引:1
Campos FR Barison A Daolio C Ferreira AG Rodrigues-Fo E 《Magnetic resonance in chemistry : MRC》2005,43(11):962-965
Complete assignments of 1H and 13C NMR chemical shifts of the polyketides aurasperone A and fonsecinone A were made by means of nuclear Overhauser enhancement and heteronuclear NMR correlation experiments. These compounds were isolated for the first time from Aspergillus aculeatus, an endophytic fungus obtained from leaves of Melia azedarach(Meliaceae). 相似文献
974.
975.
Hoebbel Dagobert Reinert Thomas Schmidt Helmut Arpac Ertugrul 《Journal of Sol-Gel Science and Technology》1997,10(2):115-126
The complexation degrees of Al-, Ti- and Zr-butoxide (M) with unsaturated and saturated -diketones (3-allylpentane-2.4-dione-APD, acetylacetone-ACAC) and -ketoesters (methacryloxyethyl-acetoacetate-MEAA, allylacetoacetate-AAA, ethylacetoacetate-EAA) as organic ligands (L) were examined by IR and 13 C NMR spectroscopy and were found to be L:M 1.5. The hydrolytic stability of the ligands of the metal alkoxide complexes (L:M = 1) during hydrolysis/condensation reactions at the molar ratio h (H2O : OR) = 0.5–2.0 decreases with increasing H
976.
M. A. Desando Y. P. Handa R. E. Hawkins C. I. Ratcliffe J. A. Ripmeester 《Journal of inclusion phenomena and macrocyclic chemistry》1990,8(1-2):3-16
The structure I clathrate hydrate of carbon monoxide has been studied using dielectric measurements and13C NMR spectroscopy. Broad, weak dielectric absorption curves with maxima at 2.2–3.8 K yieldE
a
= 0.14 kJ mol–1 for the average Arrhenius activation energy associated with the reorientation of the low polarity guest. Except for H2S this represents the fastest reorienting polar guest known among the clathrate hydrates. The low temperature dielectric absorption curves can best be fitted with a Cole-Davidson asymmetric distribution of relaxation times and activation energies (with = 0.06 at 4 × 106 Hz), which at 107 Hz has been resolved into a double symmetric distribution of discrete relaxation times for CO in the small and large cages. The cross-polarization magic angle spinning13C NMR spectra indicate identical chemical shifts for CO in the small and large cages, in contrast to other hydrates. The static spectra show that the CO molecules undergo anisotropic reorientation in the large cages and that there is still considerable mobility at 77 K. One possible model for the anisotropic motion has the CO rapidly moving among sites over each of the 14 faces of the cage with the CO axis orientated towards the cage centre. The cage occupancy ratio at 220 K,
s/
L = 1.11, indicates slightly greater preference of CO for the small cage.Dedicated to Dr D. W. Davidson in honor of his great contributions to the sciences of inclusion phenomena. 相似文献
977.
Goulart MO Machado Reys JR Emery FS Pinto AV de Souza Filho JD 《Magnetic resonance in chemistry : MRC》2004,42(7):663-665
Peroxidation of the phenazine of beta-lapachone using m-ClC6H4CO3H-CH2Cl2 furnished a macrolactone with a rigid 10-membered ring, and the corresponding N-oxide, along with a dihydrobenzophenazine-5-one. All of the new compounds were fully characterized by spectroscopic methods, with the unambiguous assignment of the hydrogens and carbon NMR signals for the N-oxide, with the aid of 2-D NMR, mainly COSY, HMQC, HSQC and HMBC. For the other two compounds some signals could not be assigned owing to their own intrinsic features. 相似文献
978.
Odlyha M. Cohen N. S. Foster G. M. Aliev A. Verdonck E. Grandy D. 《Journal of Thermal Analysis and Calorimetry》2003,71(3):939-951
DMA and solid state 13C NMR techniques were used to measure historical parchment samples within the framework of the project (MAP) Micro Analysis
of Parchment (EC contract No. SMT4-96-2101) in collaboration with the School of Conservation in Copenhagen. DMA was used in
both thermal scan and creep modes. Thermal scans provided information on the transitions associated with the collagen polymer.
Microthermal analysis was also used to obtain information on the topography and thermal conductivity of sample areas of 100
μm. Localised heating enabled measurements of softening transitions in the sample. This behaviour is influenced by the chemical
composition of parchment. 13C NMR provided information on the carbon atoms associated with the polypeptide chains of the collagen
in parchment. The behaviour of samples immersed in water and measured in DMA creep mode was used to measure the shrinkage
behaviour of the parchment samples. The different but complementary techniques provided a means for characterising the physicochemical
state of parchment samples.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
979.
Using modern NMR techniques, including DQF-COSY, NOESY, HETCOR and HMBC, the full assignments of all 1H and 13C chemical shifts were made for stigmastane-3,6-dione and stigmast-4-ene-3,6-dione, isolated from the roots of Piper nigrum (Piperaceae). Their stereochemistry was resolved by a combination of 2D NOESY data and analysis of coupling constants. The two compounds were isolated from the genus Piper for the first time. 相似文献
980.
D. L. Lipilin A. M. Churakov Yu. A. Strelenko V. A. Tartakovsky 《Russian Chemical Bulletin》2007,56(8):1566-1568
Treatment of 2-(tert-butyl-NNO-azoxy)anilines with phosgene at 20 °C was proposed as a novel route to 1,2,4-benzotriazin-3(4H )-one 1-oxides. This method involves a new reaction, viz., an intramolecular interaction of the tert-butyl-NNO-azoxy group with a C-electrophile (leading to the formation of the N(2)—C(3) bond of the triazine ring) followed by elimination
of the tert-butyl group. Complete assignment of the signals in the 1H and 13C NMR spectra of the compounds obtained was performed.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1507–1509, August, 2007. 相似文献