客体分子末端基团驱动的七元瓜环类轮烷自组装

Effects of Terminal Groups of Guest on the Pseudorotaxane Assembly of Cucurbit [7] uril

以1,2-二(4-吡啶基)乙烯为母体,设计合成了系列基于烷基链末端基团分别为—COOH,—CH_2Br和—CH_3的阳离子型线性客体分子(G1~G3).研究结果表明,末端基团为—COOH的客体分子G1可驱动七元瓜环滑过1,2-二(4-吡啶基)乙烯形成[2]类轮烷分子梭及[3]类轮烷;客体分子G2和G3则不能驱动七元瓜环滑过吡啶基乙烯母体部分,但是G2的—CH_2Br基团可驱动七元瓜环靠近吡啶基乙烯基团并形成稳定的[2]类轮烷.这一现象可归因于链状分子末端基团与瓜环端口羰基氧作用时的静电势差异.

Three guests bearing different terminal groups —COOH（ G1）,—CH2 Br（ G2） and —CH3（ G3）were synthesized based on the bispyridinium ethylene-core,respectively. The experiment results suggest that Q[7]host could slip the bispyridinium ethylene-core in the assistance of the terminal moiety —COOH of G1,and [2]pseudorotaxane based molecular shuttle could be formed between G1 and Q[7],whereas the terminal moiety —CH2 Br（ G2） and —CH3（ G3） could not help Q[7]host slip the bispyridinium ethylene-core. This could be attributed to the different electrostatic potential properties between the terminal groups of the guest and the carbonyl portals of Q[7].