Box-like Molecules-Induced Discrete Ring-in-Rings Assembly of Hydrogen-Bonded Aramide Macrocycles

The controlled formation of ring-in-ring(s) assemblies is highly desirable as precursors for constructing higher order supramolecular architectures. We report our findings that this goal can be achieved by balancing molecular structures and conformational adaptivity through an interplay of multiple non-covalent bonding interactions. With hydrogen-bonded (H-bonded) aramide macrocycles and box-like molecules including naph-Box, m-Box and p4p-Box, ring-in-rings assembling systems with 4 : 1 stoichiometry are preferentially created. The formation of such assemblies with a defined number of rings threaded on a Box molecule is unprecedented using 2D shape-persistent macrocycles. The unusual assembly behaviors are rationalized by the aid of NMR spectroscopy, mass spectrometry, X-ray crystallography, and xTB computation. In sharp contrast to the use of o-Box and p-Box in forming ring-in-rings complexes where a distribution of various assembled species is observed, the box-like molecules all afford monodisperse compact assemblies. Conformational adaptivity is deemed as one of the major factors that is accountable for the selectivity observed, which is driven mainly by cooperative action of multiple non-covalent bonding interactions including H-bonding and π-π stacking interactions. Using pyrimidyl-incorporated H-bonded macrocycles and box-like molecules to form ring-in-rings assembling structures may provide opportunities for designing more sophisticated and topologically unique supramolecular systems with potential functions.