Elastically Flexible Crystals have Disparate Mechanisms of Molecular Movement Induced by Strain and Heat

Elastically flexible crystals are an emerging class of materials that exhibit a range of notable properties. Here, we compare the mechanism of thermal expansion in flexible crystals of bis(acetylacetonato)copper(II) with the mechanism of molecular motion induced by bending and show that they are distinct. Upon bending individual molecules within the crystal structure reversibly rotate, while thermal expansion results predominantly in an increase in intermolecular separations with only minor changes to molecular orientation through rotation.