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

Abstract

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.