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 C₂-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 C₆₀ and C₇₀ 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 C₇₀ guests, further aggregation into tubular supramolecular polymers is achieved. The open-end cyclic assemblies rearrange into a closed-shell capsule upon introduction of C₆₀ with an accompanied symmetry breaking of the monomer. Our study demonstrates that a C₆₀ switch can be used to simultaneously control the topology and occupancy of tubular assemblies resulting from the aggregation of small monomers.