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71.
Johanna Camacho Gonzalez Sukanta Mondal Fernanda Ocayo Raul Guajardo-Maturana Alvaro Muñoz-Castro 《International journal of quantum chemistry》2020,120(3):e26080
The search for efficient synthetic hosts able to encapsulate fullerenes has attracted attention with regard to the purification and formation of ordered supramolecular architectures. This study of a porphyrin-based cage as an extension of the well-described ExCage6+ and BlueCage6+, involving viologen as sidearms, provides an interesting scenario where the oblate C70 fullerene is preferred in comparison to the spherical C60. Our results expose the nature of the fullerene-cage interaction involving ∼50% of dispersion-type interactions evidencing the strong π⋯π surface stacking, with a complementary contribution by the electrostatic and orbital polarization character produced by a charge reorganization with a charge accumulation facing the porphyrin macrocycles and a charge depletion along the equator formed by the viologens sidearms. Interestingly, the central N4H2 ring from each porphyrin contributes to the dispersion term via N-H⋯π interactions, which is decreased when the metallate N4Zn is evaluated. Thus, the formation of stable and selective fullerene encapsulation can be achieved by taking into account two main driving forces, namely, (a) the extension of the π⋯π and X-H⋯π stacking surface and (b) charge reorganization over the fullerene surfaces, which can be used to control fine tuning of the encapsulation thanks to the introduction of more electron-deficient and electron-rich groups within the host cage. 相似文献
72.
By applying inverse statistics to financial data it has recently been found from empirical studies that indices exhibit a pronounced gain-loss asymmetry [M.H. Jensen, Phys. Rev. Lett. 83 (1999) 76; I. Simonsen, M.H. Jensen, A. Johansen, Eur. Phys. J. B 27 (2002) 583; M.H. Jensen, A. Johansen, I. Simonsen, Physica A 324 (2003) 338]. This gain-loss asymmetry appears to have some similarities with the stylized fact leverage effect and we investigate if they could be of same origin. For this purpose we introduce the Frustration Governed Market model which includes correlations in time between a model index and its individual stocks. It is shown that the model reproduces very well the empirical findings with respect to gain-loss asymmetry and leverage. In special cases, however, the model may produce leverage without a pronounced gain-loss asymmetry. 相似文献
73.
J. Raul Alvarez-Idaboy Annia Galano Luis A. Montero Ricardo Martínez 《Journal of polymer science. Part A, Polymer chemistry》1992,30(12):2497-2502
SCF ab initio and AM1 semiempirical calculations with full geometry optimization have been carried out to model the initial steps of alkenylfuran cationic polymerization. Semiempirical procedures have been used to model propagation steps. Proton affinities of the relevant neutral species as well as the heats of formation of probable dimers were calculated. The results allow the explanation of the experimental behavior. The capabilities of the employed methods to describe these type of processes is discussed. It is confirmed that competition between vinyl and ring site attacks is the most important feature in these systems. © 1992 John Wiley & Sons, Inc. 相似文献
74.
Raul Cordovil 《Journal of Combinatorial Theory, Series B》1983,34(2):209-223
A natural sufficient condition for a finite family of single element extensions of a matroid to be compatible is given. Characterizations of all the finite extensions N of a matroid M(E) are given for which the rank function satisfies or equivalently the closure operator satisfies . The single element extensions and the principal extensions are examples of such matroids. The notion of a sheaf of flats of M. Las Vergnas is used in the proof of a new necessary and sufficient condition for two single element extensions of a matroid to be compatible. An initial announcement of part of these results appeared in R. Cordovil (C. R. Acad. Sci. Paris. A284 (1977), 1249–1252). 相似文献
75.
Fernanda M. B. Coutinho Luis C. Rezende Raul Quijada 《Journal of polymer science. Part A, Polymer chemistry》1986,24(4):727-735
A comparative kinetic study of the reaction of three different hydroxylated liquid polybutadienes (M n ? 3000) — R - 45M, R-45HT, and H-034—and tolylene diisocyanate (TDI), was carried out in toluene solution. An analytical method was used to follow the kinetics of the reactions at four different temperatures. The reactions presented an apparent second-order rate law. In the second-order plots, a discontinuity was observed. The R-45M polybutadiene was about twice more reactive than R-45HT and H-034; these latter two polybutadienes presented similar reactivities. 相似文献
76.
Dr. Edlira Suljoti Raul Garcia‐Diez Dr. Sergey I. Bokarev Dr. Kathrin M. Lange Roland Schoch Brian Dierker Marcus Dantz Kenji Yamamoto Nicholas Engel Dr. Kaan Atak Prof. Dr. Oliver Kühn Prof. Dr. Matthias Bauer Prof. Dr. Jan‐Erik Rubensson Prof. Dr. Emad F. Aziz 《Angewandte Chemie (International ed. in English)》2013,52(37):9841-9844
77.
78.
Raul SanMartín Roberto Olivera Luisa Carrillo Imanol Tellitu Maria Dolores Badía Esther Domínguez 《合成通讯》2013,43(10):1643-1652
A comparative study of the oxidation of 3-aryl-4-hydroxytetrahydroisoquinolines has been carried out. A modification of the Jones conditions turn out to be the best methodology for the regioselective preparation of target 4-isoquinolinone derivatives. 相似文献
79.
80.
Pavel Drábek Petr Girg Raul Manásevich 《NoDEA : Nonlinear Differential Equations and Applications》2001,8(3):285-298
In this paper we give a generic necessary and sufficient condition for the solvability of?
Received November 1999 相似文献