In and out! The control of the cyclotriveratrylene chirality by achiral solvents allow to switch from an open cage in polar aprotic solvents to an imploded one in bulky aromatic solvents. Interestingly, this controlled molecular motion of a cyclotriveratrylene unit is described for the first time.
Multiple Hindered Rotators in a Gyroscope-Inspired Tribenzylamine Hemicryptophane
作者:Najat S. Khan、Jose Manuel Perez-Aguilar、Tara Kaufmann、P. Aru Hill、Olena Taratula、One-Sun Lee、Patrick J. Carroll、Jeffery G. Saven、Ivan J. Dmochowski
DOI:10.1021/jo102480s
日期:2011.3.4
A gyroscope-inspired tribenzylamine hemicryptophane provides a vehicle for exploring the structure and properties of multiple p-phenylene rotators within one molecule. The hemicryptophane was synthesized in three steps in good overall yield using mild conditions. Three rotator-forming linkers were cyclized to form a rigid cyclotriveratrylene (CTV) stator framework, which was then closed with an amine. The gyroscope-like molecule was characterized by H-1 NMR and C-13 NMR spectroscopy, and the structure was solved by X-ray crystallography. The rigidity of the two-component CTV-trismethylamine stator was investigated by H-1 variable-temperature (VT) NMR experiments and molecular dynamics simulations. These techniques identified gyration of the three p-phenylene rotators on the millisecond time scale at -93 degrees C, with more dynamic but still hindered motion at room temperature (27 degrees C). The activation energy for the p-phenylene rotation was determined to be similar to 10 kcal mol(-1). Due to the propeller arrangement of the p-phenylenes, their rotation is hindered but not strongly correlated. The compact size, simple synthetic route, and molecular motions of this gyroscope-inspired tribenzylamine hemicryptophane make it an attractive starting point for controlling the direction and coupling of rotators within molecular systems.