Supramolecular Induction of Topological Chirality from Nanoscale Helical Silica Scaffolds to Achiral Molecular Chromophores

Abstract

Chiral induction from macroscopic objects possessing topological chirality to small molecules is demonstrated using nonchiral organic chromophores based on pyrene and perylene derivatives covalently grafted onto nanometric silica helices. The grafted chromophores are found to display induced chiroptical signals despite the absence of asymmetric atoms. The observed chiral induction is attributed to supramolecular chiral organization of the chromophores on the helical silica surface as evidenced by the variation of the induced circular dichroism signal with increasing surface density of the achiral chromophore. The magnitude of the induced chiroptical signals increases exponentially with the grafting density of the chromophores, suggesting that chiral induction occurs cooperatively.