Water Chains in Hydrophobic Crystal Channels: Nanoporous Materials as Supramolecular Analogues of Carbon Nanotubes
Water Chains in Hydrophobic Crystal Channels: Nanoporous Materials as Supramolecular Analogues of Carbon Nanotubes
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DOI：
10.1002/anie.201002418
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发表时间：
2010-01-01
影响因子：
16.6
通讯作者：
Davis, Anthony P.
中科院分区：
文献类型：
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作者：
Natarajan, Ramalingam;Charmant, Jonathan P. H.;Davis, Anthony P.
水在非极性窄孔中的行为引起了人们的极大兴趣。虽然看起来这些通道应该排斥水，[1]但它们可以被水合，而且它们的“疏水”性质促进了水的快速流动。这种现象在生物学中被观察到，其中水通道蛋白（水运输蛋白）的孔主要由疏水氨基酸组成。[2]根据理论[3]和实验[4]研究，碳纳米管（CNT）也可以看到这种情况，它允许水分子快速通过。通过CNT的水流可以是选择性的[5]和可控的[6]，这表明在水净化[7]和纳米流体设备中的应用。为了了解这些系统，重要的是要收集疏水环境中水的结构信息。特别相关的是“水线”，水分子的一维氢键链。水通道蛋白通道中的水采用了这种基序，[2]就像最接近和最了解的CNT中的水一样。[3a，B，e]然而，虽然有许多晶体结构显示水分子在单行中，[8]在纯疏水环境中的水线信息有限。[9]特别是似乎没有结构中的水线被包围完全由π系统。我们现在报告的晶体工程的非极性芳族单元的通道，和这些pore. We的线性链的水分子的结构表征，以前已经表明，甾体联苯脲1（图1 a）结晶为一水合物，形成结构与六角形P61对称，包含一维通道的直径异常大（图1b，c）。[10]基团R1和R2被引入通道中，因此原则上它们可以基本上变化而不破坏晶体堆积。潜在地，这应该允许用于通道大小和属性的调谐的宽范围。实际上，我们的原始报告[10]描述了三种结构1a-c，其中基团R1被改变以分别给出14.3、12.3和11.6的孔径。
The behavior of water in narrow apolar pores has attracted much recent interest. Although it might seem that such channels should repel water,[1] it transpires that they can be hydrated and moreover that their “hydrophobic” nature promotes rapid water flow. The phenomenon is observed in biology, where the pores of aquaporins (water-transporting proteins) are composed largely of hydrophobic amino acids.[2] It is also seen for carbon nanotubes (CNTs) which, according to both theoretical [3] and experimental [4] studies, allow rapid passage of water molecules. Water flow through CNTs can be selective [5] and controllable,[6] suggesting applications in water-purification [7] and nanofluidic devices. To understand these systems, it is important to gather structural information on water in hydrophobic environments. Especially relevant is the “water wire”, a one-dimensional hydrogen-bonded chain of water molecules. The water in aquaporin channels adopts this motif,[2] as does the water in the narrowest and best-understood CNTs.[3a, b, e] However, while there are many crystal structures which show water molecules in single file,[8] there is limited information on water wires in purely hydrophobic environments.[9] In particular there seem to be no structures in which water wires are surrounded exclusively by π systems. We now report the crystal engineering of channels bounded by nonpolar aromatic units, and the structural characterization of linear chains of water molecules within these pores.We have previously shown that steroidal bisphenylureas 1 (Figure 1 a) crystallize as monohydrates to form structures with hexagonal P61 symmetry, containing one-dimensional channels of unusually large diameter (Figure1b, c).[10] Groups R1 and R2 are directed into the channels, so that in principle they can be varied substantially without disrupting the crystal packing. Potentially, this should allow a broad scope for tuning of channel size and properties. Indeed, our original report [10] described three structures 1a–c, in which group R1 was altered to give pore diameters of 14.3, 12.3, and 11.6, respectively.