Stimuli-controlled self-assembly of diverse tubular aggregates from one single small monomer

The design and synthesis of new stimuli-responsive hydrogen-bonding monomers that display a diversity of self-assembly pathways is of central importance in supramolecular chemistry. Here we describe the aggregation properties of a simple, intrinsically C(2)-symmetric enantiopure bicyclic cavity compound bearing a terminally unsubstituted ureidopyrimidinone fragment fused with a pyrrole moiety in different solvents and in the absence and presence of C(60) and C(70) guests. The tetrameric cyclic aggregate is selectively obtained in chlorinated solvents, where only part of the available hydrogen bonding sites are utilized, whereas in toluene or upon addition of C(70) guests, further aggregation into tubular supramolecular polymers is achieved. The open-end cyclic assemblies rearrange into a closed-shell capsule upon introduction of C(60) with an accompanied symmetry breaking of the monomer. Our study demonstrates that a C(60) switch can be used to simultaneously control the topology and occupancy of tubular assemblies resulting from the aggregation of small monomers.