Heterochiral Diastereomer-Discriminative Diphanes That Form Hierarchical Superstructures with Nonlinear Optical Properties

In order to study the emergence of homochirality during complex molecular systems, most works mainly concentrated on the resolution of a pair of enantiomers. However, the preference of homochiral over heterochiral isomers has been overlooked, with very limited examples focusing only on noncovalent interactions. We herein report on <i>diastereomeric discrimination</i> of twin-cavity cages (denoted as <i>diphanes</i>) against heterochiral tris-(2-aminopropyl)­amine (TRPN) bearing triple stereocenters. This <i>diastereomeric selectivity</i> results from distinct spatial orientation of reactive secondary amines on TRPN. Homochiral TRPNs with all reactive moieties rotating in the same way facilitate the formation of homochiral and achiral <i>meso diphanes</i> with low strain energy, while heterochiral TRPNs with uneven orientation of secondary amines preclude the formation of cage-like entity, since the virtual <i>diphanes</i> exhibit considerably high strain. Moreover, homochiral <i>diphanes</i> self-assemble into an acentric superstructure composed of single-handed helices, which exhibits interesting nonlinear optical behavior. Such a property is a unique occurrence for organic cages, which thus showcases their potential to spawn novel materials with interesting properties and functions.