Crystals of Aliphatic Derivatives of [Cu(acac)2] have Distinct Atomic-Scale Mechanisms of Bending

Molecular crystals displaying elastic flexibility have important applications in the fields of optoelectronics and nanophotonic technologies. Understanding the mechanisms by which these materials bend is critical to the design of future materials incorporating these properties. Based on the known elastic properties of bis(acetylacetonato)copper(II), a series of 14 aliphatic derivatives are synthesized and crystallized. All those which grew in a needle morphology display noticeable elasticity, with 1D chains of pi-stacked molecules parallel to the long metric length of the crystal a consistent crystallographic feature. Crystallographic mapping is used to measure the mechanism of elasticity at an atomic-scale. Symmetric derivatives with ethyl and propyl side chains are found to have different mechanisms of elasticity, which are further distinguished from the previously reported mechanism of bis(acetylacetonato)copper(II). While crystals of bis(acetylacetonato)copper(II) are known to bend elastically via a molecular rotation mechanism, the elasticity of the compounds presented is facilitated by expansion of their pi-stacking interactions.

Automated summary

Molecular crystals of aliphatic derivatives with noticeable elasticity were synthesized and their mechanisms of elasticity were studied. Crystallographic mapping at an atomic-scale revealed that the elasticity of these compounds is facilitated by expansion of their π-stacking interactions. The findings distinguish their mechanisms from the previously reported mechanism of bis(acetylacetonato)copper(II).