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

The structural differences betweenchiral and racemiccrystalsof enantiomers have piqued interest, as exemplified by classical Wallach'srule. However, the mechanical and thermal disparities between thesematerials have not been thoroughly investigated. This study reportsthe structural and mechanical differences between chiral and racemiccrystals of two analogous molecules. The similarity of molecular andcrystal structures between the two analogues was validated throughcomparison with known chiral-racemic crystal pairs. Young'smoduli of the four crystals revealed larger values for racemic crystalsthan their chiral counterparts, consistent with the intermolecularinteraction energies projected along the loading direction. The thermalresponse of crystals plays a significant role in their elastic behavior,and the temperature dependence of interaction energies along the [001]direction was found to agree with the temperature dependence of latticedynamics for all four crystals. Inthe comparison of chiral and racemic crystals of twoanalogous compounds, it is found that racemic crystals are denserand more energetically stable and have a larger elastic modulus thanchiral crystals.