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21.
Electron paramagnetic resonance (EPR) spectra of powder and oriented films of montmorillonite, hectorite, and saponite intercalated with [Cu(cyclam)](2+) (cyclam = 1,4,8,11-tetraazacyclotetradecane) exhibit three components: an orientation-dependent component without hyperfine features, an orientation-dependent component with hyperfine features, and an orientation-independent component without hyperfine feature. EPR spectra of [Cu(cyclam)](2+)-saponite, which exhibit only two components and the best resolved hyperfine features, were simulated. The spectra indicate that a large portion of the saponite platelets are inclined to the glass surface, although they tend to align with their basal planes parallel to the glass surface. The orientation-dependent spectra could be simulated by introducing a Gaussian distribution with a standard deviation of 20 degrees for the inclination angle. The standard deviation may be used as a disorder parameter for the microcrystals assembled on glass plates. Spectral simulation also shows that the CuN(4) plane of [Cu(cyclam)](2+) is parallel to the clay layers. EPR spectra of some other partially oriented systems are also discussed. 相似文献
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Mg2Ru5B4 and Mg5Ru13B11, Two Ternary Magnesium Ruthenium Borides with Channel Structures The ternary borides Mg2Ru5B4 and Mg5Ru13B11, crystallizing in the orthorhombic space group Pbam, were prepared by reaction of the elementary components in sealed tantalum ampoules. Mg2Ru5B4 (a = 1000.0(2) pm, b = 837,6(1) pm, c = 295.42(3) pm, Z = 2, RW = 0.027 for 563 reflections) is homeotypic with Sc2Ru5B4. The structure contains BRu6-trigonal prisms, connected by faces and edges to form pentagonal channels filled with chains of magnesium atoms. Mg5Ru13B11 (a = 2190.1(2) pm, b = 996.7(2) pm, c = 294.65(3) pm, Z = 2, RW = 0.031 for 959 reflections) has a similar but so far unknown structure in which parts of the magnesium and boron atoms are disordered. 相似文献
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Michael Beyer Ramin Ghaffari-Tabrizi Michael Jung Paul Margaretha 《Helvetica chimica acta》1984,67(6):1535-1539
On acetone-sensitized irradiation the title compounds 3a–c are converted to 2-allyl-3-hydroxy-1H-pyrrole-2-carboxylates 4 in reasonable yields. 相似文献
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K. S. Jung 《Journal of Applied Mathematics and Computing》1994,1(1):49-53
Letf(n) denoted the number of essential parameters which are needed to classifyn-dimensional nilpotent Lie Algebras over the complex number field. Then $f(2n) \geqslant \tfrac{{n(n2 - 7)}}{6} - 2$ . 相似文献
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A practical synthetic route to 4-acetylisocoumarins and the first total synthesis of AGI-7 (5) and sescandelin (4) are described. The readily available homophthalate 8 was transformed to the vinylogous amide ester 13 in high overall yield. Upon treatment of 13 with refluxing aqueous formic acid, the desired 4-acetylisocoumarin (5) and its regioisomer 3-methyl-4-formylisocoumarin (17) were produced in a 3:1 ratio. After separation of the desired product (5) from the unwanted minor isomer, the enantioselective reduction of AGI-7 by borane in the presence of Corey's (S)-oxazaborolidine reagent afforded (+)-sescandelin (4) with a 93% ee. 相似文献