Designed enclosure enables guest binding within the 4200 ų cavity of a self-assembled cube

Metal-organic self-assembly has proven to be of great use in constructing structures of increasing size and intricacy, but the largest assemblies lack the functions associated with the ability to bind guests. Here we demonstrate the self-assembly of two simple organic molecules with Cd^II and Pt^II into a giant heterometallic supramolecular cube which is capable of binding a variety of mono- and dianionic guests within an enclosed cavity greater than 4200 ų. Its structure was established by X-ray crystallography and cryogenic transmission electron microscopy. This cube is the largest discrete abiological assembly that has been observed to bind guests in solution; cavity enclosure and coulombic effects appear to be crucial drivers of host-guest chemistry at this scale. The degree of cavity occupancy, however, appears less important: the largest guest studied, bound the most weakly, occupying only 11-% of the host cavity. Brobdingnagian: A giant, heterometallic cube with host-guest properties was prepared by successful application of a rational strategy to increase the dimensions whilst maintaining an enclosed cavity (see X-ray crystal structure). A variety of mono- and dianionic guests was bound in the cavity in solution. Hierarchical aggregation of the cubes into a rigid monolayer was visualized by cryogenic transmission electron microscopy.