Trapped yet Free inside the Tube: Supramolecular Chemistry of Molecular Peapods

Abstract

Abstract Supramolecular composites of carbon nanotubes and trapped fullerenes are known as peapods, and the structures of the “peapods” have been diversified by trapping many other entities in the cylindrical nanospaces. By using the molecular segments of carbon nanotubes, we have explored the supramolecular chemistries of discrete molecular peapods exhibiting atomically precise structures. In this Account, the supramolecular molecular peapod chemistry investigated in our group is reviewed. Although the peapods are assembled by weak intermolecular interactions such as van der Waals interactions and CH-π hydrogen bonds, the association force can be so tight that it results in an association constant of 1012 M−1 in solution owing to the presence of multiple interactions. These multiple interactions also enable dynamic motions of the tightly trapped guests either in the solution phase or in the solid state. The solid-state dynamic motions of the molecular peapods are particularly anomalous and can take place with ultrafast rotational frequencies in the inertial regime.