2D NMR研究对称四甲基六元瓜环与5,5'-二甲基-2,2'-联吡啶的相互作用

运用二维NMR实验研究了作为主体的对称四甲基取代六元瓜环(TMeQ6])与作为客体的5,5'-二甲基-2,2'-联吡啶(bmbpy)的相互作用.2DROESY谱上主客体分子间的NOE相关峰明确地给出了主客体的结合位置和结合物的空间结构:客体的一个吡啶环进入了主体的内腔,而另一个吡啶环则位于主体的一端端口外,进入内腔的吡啶环平面位于主体的长截面上,两个吡啶环之间为顺式构象.2DEXSY谱呈现的客体两个吡啶上对应氢之间的交换峰表明:高温下两个吡啶环交替进入主体的内腔,分别结合于主体的两个端口,形成了动态的平衡.由2DEXSY的交换峰和对角线峰强度计算出了不同温度下的交换速率,并由此得到了该交换过程的活化能为104.2kJ/mol.

2D NMR Studies on the Interaction of Symmetrical Tetramethylcucurbit[6]uril with 5,5'-Bimethyl-2,2'-bipyridine

Complexation between symmetrical tetramethylcucurbit6]uril (TMeQ6]) and 5,5'-bimethyl- 2,2'-bipyridine (bmbpy) was studied by two dimensional nuclear magnetic resonance (2D NMR) as a host-guest interaction. Intermolecular NOE to appear in 2D ROESY (Rotating Frame Overhause Effect Spectroscopy) revealed a well-defined complex structure between them. One of pyridine rings in bmbpy in- tercalated the cavity of TMeQ6] and the other was located outside one portal of TMeQ6]. Two-dimensional exchange spectroscopy (2D EXSY) showed that the complex has undergone slow ex- change at high temperature with two pyridine rings of bmbpy alternatively entering the cavity of TMeQ6] and changing the combinative sites between the two portals of TMeQ6]. The temperature dependence of the rate constants calculated from the exchange spectra yielded an activation energy of 104.2 kJ/mol for the ex- change process.