The origin of supramolecular chirality in 1-ferrocenyl amino acids.

π-Conjugated amino acids are widely applied in chiroptical materials, in which chiroptical activities are believed to originate from supramolecular packing. However, the intramolecular contribution has been largely ignored. In this work, we report that intramolecular chirality transfer behaviors in ferrocene-conjugated amino acids depend on the substituent groups, which influence the modality of multiple intramolecular interactions, as well as the molecular geometry. The structural basis and structure–property relationships of chirality and chiroptical activities were unveiled in this work. Based on single crystal structure and density functional theory calculations, we demonstrate that intramolecular weak forces, including hydrogen bonds, CH⋯π interactions and van der Waals interactions, affect the molecular geometry and contribute to diverse Cotton effects. This work provides evidence for the ignored intramolecular factors in self-assembled systems and paves the way for the fabrication of functional chiroptical systems.