Highly Stable Spherical Metallo-Capsule from a Branched Hexapodal Terpyridine and Its Self-Assembled Berry-type Nanostructure.

Discrete spherical metallo-organic capsules at the nanometer scale, especially those constructed from unique building blocks, have received significant attention recently because of their fascinating molecular aesthetics and potential applications due to their compact cavities. Here, the synthesis and characterization of a hexapodal, branched terpyridine ligand are presented along with the nearly quantitative self-assembly of the resulting tetrameric metallo-nanosphere. This metallo-nanosphere exhibited four quasi-triangular and six rhombus-like facets, all of which were made by the same hook-like bis-terpyridine. Collision-induced dissociation experiments were done to investigate overall stability. The metallo-architecture and host-guest chemistry were investigated with coronene and fully characterized by 1D and 2D NMR, ESI-MS, and transmission electron microscopy. Furthermore, this metallo-nanosphere was observed to hierarchically self-assemble into berry-type structures in an acetonitrile/methanol mixture, by virtue of counterion-mediated attractions. The functional molecular metallo-nanosphere presented here expands the reach of terpyridine coordination systems into molecular containers and other model systems.