Nakano Kazunori, Aburaya Kazuaki, Hisaki Ichiro, Tohnai Norimitsu, Miyata Mikiji
Nagoya Municipal Industrial Research Institute, 3-4-41 Rokuban, Atsuta-ku, Nagoya 456-0058, Japan.
Chem Rec. 2009;9(2):124-35. doi: 10.1002/tcr.20171.
We have systematically investigated structures and properties of inclusion crystals of bile acids and their derivatives. These steroidal compounds form diverse host frameworks having zero-, one- and two-dimensional cavities, causing various inclusion behaviors towards many organic compounds. The diverse host frameworks exhibit the following guest-dependent flexibility. First, the frameworks mainly depend on the included guests in size and shape. The size-dependence is quantitatively estimated by the parameter PCcavity, which is the volume ratio of a guest molecule to a host cavity. The resulting values of PCcavity lie in the range of 42-76%. Second, each of the host frameworks has its own range of the values. Some guests can employ two different frameworks with the boundary values, explaining formation of polymorphic crystals. Third, the host frameworks are selected by host-guest interactions through weak hydrogen bonds, such as NH/pi and CH/O. The weak hydrogen bonds play an important role for various selective inclusion processes. Fourth, the host frameworks are dynamically exchangeable, resulting in intercalation and polymerization in the cavities. These static and dynamic structures of the frameworks demonstrate great potential of crystalline organic inclusion compounds as functional materials.
我们系统地研究了胆汁酸及其衍生物包合晶体的结构和性质。这些甾体化合物形成了具有零维、一维和二维空腔的多样主体框架，对许多有机化合物表现出各种包合行为。多样的主体框架表现出以下依赖客体的灵活性。首先，框架在尺寸和形状上主要取决于所包含的客体。尺寸依赖性通过参数PCcavity进行定量估计，PCcavity是客体分子与主体空腔的体积比。PCcavity的所得值在42 - 76%的范围内。其次，每个主体框架都有其自身的值范围。一些客体可以采用具有边界值的两种不同框架，这解释了多晶型晶体的形成。第三，主体框架通过诸如NH/π和CH/O等弱氢键的主客体相互作用来选择。弱氢键在各种选择性包合过程中起重要作用。第四，主体框架是可动态交换的，导致空腔中的插层和聚合。框架的这些静态和动态结构证明了结晶有机包合化合物作为功能材料的巨大潜力。
