Department of Chemistry, Northwestern University, Evanston, IL 60208, USA.
Proc Natl Acad Sci U S A. 2010 Aug 10;107(32):13991-6. doi: 10.1073/pnas.1009302107. Epub 2010 Jul 27.
The template-directed synthesis of a bistable donor-acceptor [2]catenane wherein both translational isomers--one in which a tetrathiafulvalene unit in a mechanically interlocked crown ether occupies the cavity of a cyclobis(paraquat-p-phenylene) ring and the other in which a 1,5-dioxynaphthalene unit in the crown ether resides inside the cavity of the tetracationic cyclophane--exist in equilibrium in solution, has led to the isolation and separation by hand picking of single crystals colored red and green, respectively. These two crystalline co-conformations have been characterized separately at both the molecular and supramolecular levels, and also by dynamic NMR spectroscopy in solution where there is compelling evidence that the mechanically interlocked molecules are present as a complex mixture of translational, configurational, and conformational isomers wherein the isomerization is best described as being a highly dynamic and adaptable phenomenon.
一种双稳态给体-受体[2]轮烷的模板导向合成,其中两种平移异构体——一种是机械互锁冠醚中的四硫富瓦烯单元占据环双(对亚甲基苯醌-对苯撑)环的空腔,另一种是冠醚中的 1,5-二氧萘单元位于四阳离子环轮烷的空腔内——在溶液中处于平衡状态,导致通过手工挑选分别分离出红色和绿色的单晶。这两种晶态共构分别在分子和超分子水平上进行了表征,并且通过溶液中的动态 NMR 光谱也进行了表征,其中有令人信服的证据表明,机械互锁分子作为平移、构象和构象异构体的复杂混合物存在,其中异构化最好被描述为一种高度动态和适应性强的现象。