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991.
Dr. Gabriel Canard Dr. Di Gao Dr. Anthony D'Aléo Dr. Michel Giorgi Florian‐Xuan Dang Prof. Dr. Teodor Silviu Balaban 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(21):7760-7771
The introduction of ester groups on the 5‐ and 15‐meso positions of corroles stabilizes them against oxidation and induces a redshift of their absorption and emission spectra. These effects are studied through the photophysical and electrochemical characterization of up to 16 different 5,15‐diester corroles, in which the third meso position is free or occupied by an aryl group, a long alkyl chain, or an ester moiety. Single‐crystal X‐ray structure analysis of five 5,15‐diestercorroles and DFT and time‐dependent DFT calculations show that the strong electron‐withdrawing character of the 5,15 ester substituents is reinforced by their π overlap with the macrocyclic aromatic system. The crystal packing of corroles 2 , 4 , 6 , 9 , and 15 features short distances between chromophores that are stacked into columns thanks to the low steric hindrance of meso‐ester groups. This close packing is partially due to intermolecular interactions that involve inner hydrogen and nitrogen atoms, and thereby, stabilize a single, identical corrole tautomeric form. 相似文献
992.
Inside Cover: An Efficient Synthesis of Porphyrins with Different meso Substituents that Avoids Scrambling in Aqueous Media (Chem. Eur. J. 4/2015) 下载免费PDF全文
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Alba Vargas‐Caamal Jose Luis Cabellos Filiberto Ortiz‐Chi Henry S. Rzepa Albeiro Restrepo Gabriel Merino 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(8):2812-2818
The potential energy surfaces of the HCl(H2O)n (n is the number of water molecules) clusters are systematically explored using density functional theory and high‐level ab initio computations. On the basis of electronic energies, the number of water molecules needed for HCl dissociation is four as reported by some experimental groups. However, this number is five owing to the inclusion of entropic factors. Wiberg bond indices are calculated and analyzed, and the results provide a quadratic correlation and classification of clusters according to the nondissociated, partially dissociated, and fully dissociated character of the H?Cl bond. Our computations show that if temperature is not controlled during the experiment, the values obtained for the dipole moment (or for any measurable property) are susceptible to change, providing a different picture of the number of water molecules needed for HCl dissociation in a nanoscopic droplet. 相似文献
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Jean-Pierre Gabriel Joseph Hersch 《Zeitschrift für Angewandte Mathematik und Physik (ZAMP)》1971,22(1):210-215
Summary For the first eigenvalue 1 of a vibrating membrane, the «method of one-dimensional auxiliary problems» gave the lower bounds (19). We present here two new interpretations of those bounds, by means of cutting the membrane either into infinitesimal strips or else into infinitesimal quadratic cells, and adding positive or negative elastic support on each side of each cut. 相似文献
1000.
Ernst Lücker Horst K?nig Wolfgang Gabriel Anton Rosopulo 《Fresenius' Journal of Analytical Chemistry》1992,342(12):941-949
Summary The function of solid sampling graphite furnace atomic absorption spectrometry (SS-GFAAS) in the laboratory-internal preparation, production and standardization of several animal tissue reference materials is described. SS-GFAAS is successfully applied in the production of a bovine liver reference material with a low content of Pb and Cd. The lab-internal production of 5 bovine teeth and 2 bovine bone reference materials illustrates some of the basic problems entailed in the analysis of Pb in osseus matrices and in the production of the reference material itself. In the production of muscle tissue reference material focal or generalized calcification is a serious source of endogenous Pb contamination. This is shown, by way of example, in the calcification of the larval states of Taenia saginata (Cysticercus bovis) in the bovine muscle. Finally, as further examples of the application of SS-GFAAS, the lab-internal production of reference material from bovine blood and equine renal cortex is described. 相似文献