Kinetic and thermodynamic effects in the self-assembly of [3]catenanes in the solution and solid states

A change in the constitution of the tetracationic cyclophane components (comprised of two paraquat residues bridged by either m- or p-phenylene rings) in [2]catenanes, where the other macrocyclic components are polyethers (incorporating two π-electron-rich rings, such as 1,4-dioxybenzene or 1,5-dioxynaphthalene, located symmetrically within a crown-10 structure) not only affects the efficiencies but also the selectivities associated with the self-assembly processes that lead to the formation of interlocked molecular compounds. The self-assembly of two new [2]catenanes - composed of cylo-(paraquat-p-phenylene-paraquat-m-phenylene) and either 1,5-dinaphtho-38-crown-10 (1/5DN38C10) or 1,5-naphtho-p-phenylene-36-crown-10 (1/5NPP36C10) - is accompanied by the formation, in each case, of a [3]catenane incorporating a dimer of the tetracationic cyclophane and one or other of the two macrocyclic polyethers. A mechanistic rationale, based on thermodynamic and kinetic considerations, is presented to explain the formation of the dimeric octacationic products. The X-ray crystal structures of the two [3]catenanes reveal the dominance of π-π stacking interactions both within the molecules and beyond them where highly distinctive brick-like and parquet-like packing motifs are observed.