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首页> 外文期刊>Crystal growth & design >Structural Characterization of Pyrrolidine-Including Structure II Clathrate Hydrates
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Structural Characterization of Pyrrolidine-Including Structure II Clathrate Hydrates

机译：吡咯烷的结构表征 - 包括结构II包合物水合物

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摘要

Clathrate hydrates are host-guest crystalline compounds which can capture both small gases such as H-2, CH4, and CO2 and larger guest molecules which are in the liquid state. Large guests (LGs) such as tetrahydrofuran (THF) can strongly stabilize the structure II clathrate hydrate under moderate conditions and provide a substantial number of small cages for the encapsulation of smaller guest gases. Most hydrocarbon LGs are volatile and immiscible in water, and even the water-miscible LGs such as THF are still volatile. The use of these LGs requires a recovery process in applications based on hydrates. Amines are one chemical group of alternative LGs which have low vapor pressure compared to hydrocarbon LGs. In this study, we report structural characterization for clathrate hydrates formed with the cyclic amine pyrrolidine (PL) and the structurally related THF. Crystal samples were formed from aqueous solutions of PL and THF with several ratios. Lattice constants determined by the single-crystal X-ray diffraction increased with the increase of PL content in the hydrate. Inspection of the cage size found that 5(12)6(4) cages expand due to PL inclusion, while the empty 5(12) cages do not expand to the same degree. The refined X-ray diffraction structure suggests that the PL is incorporated in the large cage without forming hydrogen bonds with the cage water molecules. Molecular dynamics simulations also support weak hydrogen bond interactions between PL and water molecules.
机译：笼形水合物是主客体晶体化合物，可以捕获小气体（如H-2、CH4和CO2）和较大的液态客体分子。在中等条件下，四氢呋喃（THF）等大客体（LGs）可以强烈稳定结构II笼形水合物，并为封装较小客体气体提供大量小笼状物。大多数碳氢化合物LGs是挥发性的，不溶于水，即使是水溶性LGs，如THF，仍然是挥发性的。在基于水合物的应用中，使用这些LGs需要一个恢复过程。胺是替代LGs的一个化学组，其蒸汽压比碳氢化合物LGs低。在这项研究中，我们报告了由环胺吡咯烷（PL）和结构相关的THF形成的笼形水合物的结构表征。晶体样品由PL和THF的水溶液按不同比例形成。单晶X射线衍射测定的晶格常数随着水合物中PL含量的增加而增加。对保持架尺寸的检查发现，5（12）6（4）个保持架因PL夹杂物而膨胀，而空的5（12）个保持架膨胀程度不同。精细的X射线衍射结构表明，PL被纳入大笼中，而不会与笼水分子形成氢键。分子动力学模拟也支持PL和水分子之间的弱氢键相互作用。

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