Department of Chemistry and Biochemistry, 236 Nieuwland Science Hall, University of Notre Dame, Notre Dame, Indiana 46556, United States.
J Org Chem. 2011 Jan 21;76(2):688-91. doi: 10.1021/jo1020739. Epub 2010 Dec 17.
The structural dynamics of two pairs of [2]rotaxanes were compared using variable-temperature NMR. Each rotaxane had a surrounding tetralactam macrocycle with either 2,6-pyridine dicarboxamide or isophthalamide bridging units. Differences were observed in two types of rotational processes: spinning of the phenylene wall units in the surrounding macrocycle of squaraine rotaxanes and macrocycle pirouetting in xanthone rotaxanes. The rotaxanes with macrocycles containing 2,6-pyridine dicarboxamide bridges exhibited higher rotational barriers due to a cavity contraction effect, which disfavored macrocycle breathing.
采用变温 NMR 比较了两对[2]轮烷的结构动力学。每个轮烷都有一个周围的四元环酰胺大环，其中 2,6-吡啶二甲酰胺或间苯二甲酰胺桥联单元。在两种旋转过程中观察到差异：方酸轮烷中环庚三烯酚部分的苯环壁单元的旋转和黄烷酮轮烷中环的旋转。由于腔收缩效应，含有 2,6-吡啶二甲酰胺桥联单元的大环轮烷的旋转势垒较高，不利于大环呼吸。
