Unraveling the Structural and Property Differences Between Highly Similar Chiral and Racemic Crystals Composed of Analogous Molecules

The structural differences between chiral and racemic crystals of enantiomers have piqued interest, as exemplified by the classical Wallach's rule. However, the mechanical and thermal disparities between these materials have not been thoroughly investigated. This study reports the structural and mechanical differences between chiral and racemic crystals of two analogous molecules. The similarity of molecular and crystal structures between the two analogs was validated through comparison with known chiral-racemic crystal pairs. The Young's moduli of the four crystals revealed larger values for racemic crystals than their chiral counterparts, consistent with the intermolecular interaction energies projected along the loading direction. The thermal response of crystals plays a significant role in their elastic behavior, and the temperature dependence of interaction energies along [001] direction was found to agree with the temperature dependence of lattice dynamics for all four crystals.