Oxtoby Neil S, Blake Alexander J, Champness Neil R, Wilson Claire
School of Chemistry, University of Nottingham, University Park, UK.
Chemistry. 2005 Aug 5;11(16):4643-54. doi: 10.1002/chem.200500091.
A strategy for encouraging the formation of extended water arrays is presented, in which molecules that contain a 1,4-dihydroquinoxaline-2,3-dione core are used as supramolecular hosts for the accommodation of guest water molecules and arrays. These molecules were selected as they contain a hydrophilic oxalamide-based "terminus" that allows water molecules to hydrogen-bond to the host organic molecules as well as to each other. The host molecules also contain a hydrophobic "end" based upon an aromatic ring, which serves to encourage the formation of discrete water clusters in preference to three-dimensional networks, as the water molecules cannot form strong hydrogen bonds with this part of the molecule. A systematic study of several hydrated structures of four organic molecules based on 1,4-dihydroquinoxaline-2,3-dione (qd) is discussed. The organic molecules, qd, 6-methyl-1,4-dihydroquinoxaline-2,3-dione (mqd), 6,7-dimethyl-1,4-dihydroquinoxaline-2,3-dione (dmqd) and 1,4-dihydrobenzo[g]quinoxaline-2,3-dione (Phqd), act as supramolecular crystal hosts for the clusters of water, with zero-, one- and two-dimensional arrays of water being observed. The hydrogen bonding in the structures, both within the water clusters and between the clusters and organic molecules, is examined. In particular, the structure of dmqd6 H2O contains a two-dimensional water sheet composed of pentagonal and octagonal units. Phqd3 H2O forms a hydrophilic extended structure encouraging the formation of one-dimensional chains consisting entirely of water. Both qd2 H2O and dmqd2 H2O can be considered to form one-dimensional chains, but only by utilising bridging carbonyl groups of the oxalamide moieties to form the extended array; if only the water is considered, zero-dimensional water tetramers are observed. The remaining hydrated structures, [Na+dmqd-]dmqdH2O, dmqd1/3H2O and mqd1/2H2O, all contain discrete water molecules but do not form extended water structures.
本文提出了一种促进扩展水阵列形成的策略，其中含有1,4 - 二氢喹喔啉 - 2,3 - 二酮核心的分子被用作超分子主体，用于容纳客体水分子和阵列。选择这些分子是因为它们含有基于草酰胺的亲水性“末端”，这使得水分子能够与主体有机分子以及彼此之间形成氢键。主体分子还含有基于芳香环的疏水性“末端”，由于水分子不能与该分子部分形成强氢键，这有助于优先形成离散的水簇而非三维网络。讨论了对基于1,4 - 二氢喹喔啉 - 2,3 - 二酮（qd）的四种有机分子的几种水合结构的系统研究。有机分子qd、6 - 甲基 - 1,4 - 二氢喹喔啉 - 2,3 - 二酮（mqd）、6,7 - 二甲基 - 1,4 - 二氢喹喔啉 - 2,3 - 二酮（dmqd）和1,4 - 二氢苯并[g]喹喔啉 - 2,3 - 二酮（Phqd）作为水簇的超分子晶体主体，观察到了零维、一维和二维的水阵列。研究了结构中的氢键，包括水簇内部以及簇与有机分子之间的氢键。特别地，dmqd·6H₂O的结构包含由五边形和八边形单元组成的二维水层。Phqd·3H₂O形成了一种亲水性扩展结构，促进了完全由水组成的一维链的形成。qd·2H₂O和dmqd·2H₂O都可以被认为形成了一维链，但这仅通过利用草酰胺部分中的桥连羰基来形成扩展阵列；如果仅考虑水，则观察到零维水四聚体。其余的水合结构，[Na⁺dmqd⁻]dmqd·H₂O、dmqd¹/₃H₂O和mqd¹/₂H₂O，都包含离散的水分子，但不形成扩展的水结构。
