Visualizing Solid-State Molecular Motion by a Common Structural Determination Technique

Solid-state molecular motion plays a vital role in many advanced technologies. However, visualization of these processes is still challenging due to the limitation of characterization method. In this work, a common structural determination technique, single-crystal X-ray diffraction, is applied to “see” the static and dynamic molecular motions in tetraphenylethylene (TPE) which exhibits aggregation-induce emission (AIE) effect. Five kinds of motions, stretching, torsion, twisting, rocking, and wagging are observed and analyzed. As the static molecular motions, the middle double bond in TPE becomes short and twisted and the peripheral phenyl rings as a whole tend to be more twisted with the raising of testing temperature (150 to 298 K). Meanwhile, dynamic motions of phenyl-rings rocking and wagging are found to be more and more vigorous along with the increase of temperature. This work provides a platform for visualizing solid-state molecular motion based on a common technique. It also affords direct evidence for the AIE mechanism of restriction of intramolecular motions.