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991.
In the presence of 5 mol% Sc(OTf)3, double indolylation of acetic acid 2-methylene-3-oxo-butyl ester with differently substituted indoles readily afforded beta,beta-bis(indolyl) ketones. The reaction may proceed via a Sc(OTf)3-catalyzed SN2'-type substitution and subsequent conjugate addition. 相似文献
992.
Crystal and molecular structures of the planar neutral ligand, C26H16N8, and the four isomorphous five-coordinated metal complexes, [M(C26H16N8)(H2O)], M = Mn(II), Co(II), Cu(II), Zn(II), have been determined from three-dimensional X-ray diffraction data. The free ligand hpH2, C26H16N8, belongs to the P 21/c space group with Z=2, a=4.142(3), b=23.736(6), c=10.338(3) Ä, β=94.66(6)°. The metal complexes monohydrate Mhp-H2O all belong to the orthorhombic Pcab space group with Z=8. The dimensions are roughly 8.8×19.3×23.7 Å3. In each structure, the macrocyclic ligand has an almost planar conformation which differs from the saddle shaped ligand hydrate (hpH2·H2O) and the nickel complex [Nihp]5. The distances from the center of the macrocyclic ring to the nitrogen atom of the free ligand are 1.907(6) and 2.245(6)Å. The coordination geometry in these four complexes is square pyramidal with a water molecule as an axial ligand. The bond distances of M(II)-O(H2O), M(II)-N1 (imine), M(II)-N3 (pyridine) are: 2.19(1), 2.00(2), 2.27(2)Å respectively for the manganese complex; 2.08(1), 1.97(1), 2.23(1)Å for the cobalt complex; 2.33(1), 1.92(3), 2.18(1)Å for the copper complex; 2.110(5), 1.964(6), 2.252(6)Å for the zinc complex. The variation of metal-ligand distances can be correlated to the metal d orbital occupancy. A comparison with similar ligands will be presented. 相似文献
993.
Yu.Ya. Gurevich M.D. Krotova Yu.V. Pleskov 《Journal of Electroanalytical Chemistry》1977,75(1):339-351
The laws of photoemission into electrolyte solutions from semiconductor electrodes have been studied theoretically and experimentally. Relations have been obtained for the frequency dependence of the photoemission current with allowance for the photogeneration of electrons by the direct and indirect transition mechanisms. The experimentally obtained dependence of the photoemission current from n- and p-type germanium and p-type gallium arsenide electrodes in aqueous solution on the light quantum energy, and at sufficiently negative potentials also on potential, is described by the three-halves law, characteristic of direct transitions in the bulk. A band scheme of the system has been constructed, from which the value of the semiconductor-solution Volta potential and the value of the potential in the space charge region of semiconductor have been found. 相似文献
994.
The literature on operational calculus and its applications, reviewed in Referativnyi Zhurnal Matematika during 1965–1977, is surveyed.Translated from Itogi Naukl i Tekhniki, Seriya Matematicheskii Analiz, Vol. 16, pp. 99–148, 1979. 相似文献
995.
D. Yu. Grigor'ev 《Journal of Mathematical Sciences》1981,17(4):1987-1998
The concept of multiplicative complexity of a bilinear form is introduced for a commutative Noetherian ring. Rings are described for which the multiplicative complexity coincides with the rank for all forms. It is shown that for regular rings of dimension 3 the multiplicative complexity can exceed the rank by an arbitrarily large number.Translated from Zapiski Nauchnykh Seminarov Leningradskogo Otdeleniya Matematicheskogo Instituta im. V. A. Steklova, Vol. 86, pp. 66–81, 1979. 相似文献
996.
M. F. Bolotnikov Yu. A. Neruchev 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2006,80(8):1191-1197
The enthalpies of vaporization of 1-chloroalkanes containing n = 3–20 carbon atoms were calculated from saturated vapor pressure data. It was shown that the enthalpies of vaporization of 1-chloroalkanes could be calculated on the basis of model concepts of the structure of liquids from experimental liquid density and sound velocity data. 相似文献
997.
Yu. M. Zinoviev 《Communications in Mathematical Physics》1976,47(1):33-42
n-point Lorentz invariant tempered distributions with the supports for one-point only in
are described. 相似文献
998.
The assembly of[Et4N][Tp*WS3](1) with CuX (Tp* =hydridotris(3,5-dimethylpyrazol-1-yl)borate;X =Cl,Br,and I) or[Cu(MeCN)4][PF6]in the presence of tetratopic liga... 相似文献
999.
锗在国防工业、航空航天和通信等领域中的战略性,锗含量的测定对于保证材料质量和满足国际标准至关重要。本文综述了锗含量测定方法的多种技术,包括分光光度法、原子荧光光谱法、原子吸收光谱法、电感耦合等离子体原子发射光谱法、电感耦合等离子体质谱法以及滴定法。在每个检测方法的介绍中,详细探讨了方法的原理、前处理步骤以及应用范围,并分别总结了各个方法的优势和不足。最后,强调了锗含量测定方法的意义,特别是在满足出口监管和促进科学研究方面的作用。同时对锗元素的测定方法进行了展望,为未来的发展提供了参考方向。 相似文献
1000.