Guest binding and orientation within open nanoscale hosts
Guest binding and orientation within open nanoscale hosts
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DOI：
10.1002/chem.200390008
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发表时间：
2003-01-03
影响因子：
4.3
通讯作者：
Gibb, BC
中科院分区：
文献类型：
--
作者：
Laughrey, ZR;Gibb, CLD;Gibb, BC
报道了三种不同纳米级分子主体的合成。这些空腔均拥有一个高度预组织的空腔，带有一个开放的入口（近 1 nm 宽），客人可以通过该入口进出该空腔。此外，这些主体通过弱酸性苯亚甲基 C-H 基团进行深度功能化，可以与空腔内的客体分子形成各种非共价相互作用。研究人员对 31 名客人与主人产生情结的倾向进行了检查。具有卤素原子的客体是最强的结合剂，表明与苯甲醛氢的深冠形成多齿C-H...X-R氢键。注意到自由态和结合态之间的交换率取决于客体的大小和用于研究络合的溶剂。一般来说，在 DMSO 中与高度互补的客体进行络合时，结合力更强，交换速度更慢。使用 EXSY NMR 光谱或 H-1 NMR 位移数据确定空腔内每种客体的取向。总的来说，这些结果表明，指导取向的主要因素是与苯甲醛基团和溶剂类型的相互作用。还对选定的络合进行了范特霍夫分析。这些实验不仅揭示了所有络合在熵上都是不利的，还为客体取向的确定提供了支持，并估计了 C-H...I-R 氢键的形成释放了 1 至 1.5 kcal mol(-1) 之间的能量。
The synthesis of three different nanoscale molecular hosts is reported. These cavitands each possess a highly preorganized cavity with an open portal (nearly 1 nm wide), by which guests can enter and egress the cavity. Additionally, these hosts are deep-functionalized with a crown of weakly acidic benzal C-H groups which can form a variety of noncovalent interactions with guest molecules residing within the cavity. Thirty-one guests were examined for their propensity to form complexes with the hosts. Guests that possess halogen atoms were the strongest binders, suggesting the formation of polydentate C-H...X-R hydrogen bonds with the deep crown of benzal hydrogens. Exchange rates between the free and bound states were noted to be dependent on the size of the guest and the solvent used to study complexation. In general, stronger binding and slower exchange were noted for complexations carried out in DMSO with highly complementary guests. The orientation of each guest within the cavity was determined using either EXSY NMR spectroscopy or H-1 NMR shift data. Cumulatively these results showed that the principal factors directing orientation were interactions with the benzal groups and the type of solvent. Van't Hoff analyses of selected complexations were also carried out. As well as revealing that all complexations were entropically unfavorable, these experiments provided support for guest orientation determinations, and gave an estimation that the formation of a C-H...I-R hydrogen bond releases between 1 and 1.5 kcal mol(-1).