Elaborate Supramolecular Architectures Formed by Co-Assembly of Metal Species and Peptoid Macrocycles

Peptoids are a family of sequence-specific oligomers capable of mimicking the structure and function of polypeptides. The innate folding and self-assembly capabilities of peptoid oligomers can be enhanced by the presence of coordinated metal ions. In this work, we explore the co-assembly of water-soluble hexameric and tetrameric peptoid macrocycles with Na+ and K+ ions. Solid-state structures were solved for six cyclopeptoid-metal coassemblies by X-ray diffraction using single crystals grown from fully aqueous solutions. Subtle variations in the peptoid oligomer composition give rise to dramatic alterations in the supramolecular assemblies. Some structures feature extensively hydrated porous architectures that include unusual metal ion clusters. The ability to study the metallopeptoid structure at an atomic resolution in crystals obtained from an aqueous solution is an important advancement, as most previous peptoid crystal structures were obtained from nonaqueous or cosolvent solutions. These results will facilitate the design of peptoids and other foldamers for the assembly of supramolecular frameworks.