The synthesis of mechanically interlocked carbon nanotube (MINT) derivatives relies on a templating step in which the macrocycle precursors adsorb onto single-walled carbon nanotubes (SWCNTs). The relative roles of the different thermodynamic contributions to the supramolecular recognition step remain poorly understood. Herein, we quantify the binding affinity of U-shaped macrocyclic precursors differing in their aromatic content, from pyrene or anthraquinone to flexible diphenylmethane. Thermogravimetric analysis-based titrations show that precursors bearing extended aromatic recognition motifs bind over an order of magnitude more strongly to (6,5)-SWCNT at room temperature than their phenyl analogues. Quantum chemical calculations and explicit-solvent molecular dynamics simulations quantify the relative importance of the different interactions. We find that π-extended recognition motifs engage in stronger aromatic stacking interactions and restrict conformational freedom. Aliphatic side chains enhance binding, despite larger deformation and conformational entropy penalties. These insights offer molecular design rules for macrocycles that optimize preorganization and facilitate MINT formation.
Silva et al. (Tue,) studied this question.