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Identifying the shape of copper-seamed nanocapsules in solution

Nanoscale materials based on the bowl-shaped molecules of the calixarene family continue to capture the imagination of the scientific community with potential applications in pharmaceuticals, catalysis, and as molecular magnets. In the design of a complex supramolecular solid-state structure, a question always arises: what does the solid-state structure teach about the species present in solution? The answer to this question is typically based on nuclear magnetic resonance (NMR) evidence or sheer speculation.

Measurements utilizing the CHRNS-supported SANS instrument answer this question, revealing that PgC11Cu and PgC13Cu hexamers in solution form core-shell nanocapsules, and PgC17Cu, which contains longer alkyl side chains, forms interdigitated ellipsoidal chains. Longer alkyl groups facilitate interlocking of capsules into multi-capsule assemblies that mimic biological membranes connecting two adjacent cells. SANS measurements have proven valuable in determining the solution structure of species that are difficult to crystallize and hence solid-state structure determination is not possible.

Dan Neumann, National Institute of Standards and Technology, DMR 0944772

single alkylpyrogallol[4]arene bowl

hexamer

chain of capsules