Molecular Compasses and Gyroscopes: Engineering Molecular Crystals with Fast Internal Rotation

Crystals of 1,4-bis[3,3,3-tri(3,4-ditertbutyl)phenylpropynyl]benzene 1c may be viewed as a collection of molecular gyroscopes having a central p-diethynylphenylene as a rotary element encased by two bulky triarylmethyl groups. Single-crystal X-ray analysis, 13C CPMAS NMR, and 2H NMR quadrupolar-echo line-shape analysis revealed a lattice of molecules with phenylene groups experiencing rotary motion in the gigahertz regime near ambient temperature.1,4-双[3,3,3-三(3,4-二叔丁基)苯丙炔基]苯1c的晶体可被视为一类分子陀螺仪的集合，其以对二乙炔基亚苯基（p-diethynylphenylene）作为中心旋转组件，外部被两个大体积三芳基甲基基团包裹。通过单晶X射线分析、碳-13交叉极化魔角旋转核磁共振（13C CPMAS NMR）以及氘-2核磁共振（2H NMR）四极回波线形分析，研究发现该分子晶格中的亚苯基基团在室温附近的吉赫兹频段内发生旋转运动。