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Efrem Braun Dr. Joseph J. Chen Dr. Sondre K. Schnell Dr. Li‐Chiang Lin Dr. Jeffrey A. Reimer Dr. Berend Smit 《Angewandte Chemie (International ed. in English)》2015,54(48):14349-14352
Molecular simulations and NMR relaxometry experiments demonstrate that pure benzene or xylene confined in isoreticular metal–organic frameworks (IRMOFs) exhibit true vapor–liquid phase equilibria where the effective critical point may be reduced by tuning the structure of the MOF. Our results are consistent with vapor and liquid phases extending over many MOF unit cells. These results are counterintuitive since the MOF pore diameters are approximately the same length scale as the adsorbate molecules. As applications of these materials in catalysis, separations, and gas storage rely on the ability to tune the properties of adsorbed molecules, we anticipate that the ability to systematically control the critical point, thereby preparing spatially inhomogeneous local adsorbate densities, could add a new design tool for MOF applications. 相似文献
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Melanie Schnell Dr. Gerard Meijer Prof. Dr. 《Angewandte Chemie (International ed. in English)》2009,48(33):6010-6031
Research with cold molecules has developed rapidly in recent years. There is now a variety of established methods for cooling molecules into the millikelvin range. Nevertheless, a focal point of current research is directed toward finding new ways to bring the temperature of molecules even closer to absolute zero. Samples of cold molecules offer not only important applications for high‐resolution spectroscopy, which benefit from the increased interaction time of slow molecules with electromagnetic radiation; they also promise access to an exotic regime of chemical reactivity, in which phenomena such as quantum tunneling and quantum resonances predominate. This review begins with an introduction to the methods by which cold molecules can be prepared, with special emphasis on Stark deceleration and traps. In addition to applications of cold molecules that have already been partially achieved, an important focus of the review concentrates on possible future applications, and both aspects are illustrated with selected examples. 相似文献
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An identity for the volume of projections of parallelotopesis proved, where a kind of dual parallelotopeis used. This identity generalizes a result on the unit cubeby P. McMullen 相似文献
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E. Constantin A. Schnell F. Guidugli P. Traldi 《Journal of mass spectrometry : JMS》1992,27(3):174-178
The collision-induced decomposition pathways of phenothiazine were studied in detail by ion trap mass spectrometry. With this approach, different amounts of energy can be deposited into the fragment ions, thus favouring particular structures. Different relative abundances in the fragmentation patterns of selected ions are observed, depending on whether they are produced by electron impact or multiple mass spectrometry [(MS)n] methods. 相似文献
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Martin Schulz-Dobrick Thorsten Metzroth Hans Wolfgang Spiess Jürgen Gauss Ingo Schnell 《Chemphyschem》2005,6(2):315-327
The structure of multiply hydrogen-bonded systems is determined with picometer accuracy by a combined solid-state NMR and quantum-chemical approach. On the experimental side, advanced 1H-15N dipolar recoupling NMR techniques are capable of providing proton-nitrogen distances of up to about 250 pm with an accuracy level of +/-1 pm for short distances (i.e., around 100 pm) and +/-5 pm for longer ones (i.e., 180 to 250 pm). The experiments were performed under fast magic-angle spinning, which ensures sufficient dipolar decoupling and spectral resolution of the 1H resonance lines. On the quantum-chemical side, the structures of the hydrogen-bonded systems were computationally optimised, yielding complete sets of nitrogen-proton and proton-proton distances, which are essential for correctly interpreting the experimental NMR data. In this way, nitrogen-proton distances were determined with picometer accuracy, so that vibrational averaging effects on dipole-dipole couplings need to be considered. The obtained structures were finally confirmed by the complete agreement of computed and experimental 'H and '5N chemical shifts. This demonstrates that solid-state NMR and quantum-chemical methods ideally complement each other and, in a combined manner, represent a powerful approach for reliable, high-precision structure determination whenever scattering techniques are inapplicable. 相似文献