Supramolecular Shish Kebabs: Higher Order Dimeric Structures from Ring-in-Rings Complexes with Conformational Adaptivity.

Use of abiotic chemical systems for understanding higher order superstructures is challenging. Here we report a ring-in-ring(s) system comprising a hydrogen-bonded macrocycle and cyclobis(paraquat-o-phenylene) tetracation ( o-Box) or cyclobis(paraquat-p-phenylene) tetracation (CBPQT4+, p-Box) that fulfills the construction of discrete higher order structures with adaptive conformation. As indicated by mass spectrometry, computational modeling, NMR, and single crystal X-ray diffraction, this ring-in-ring(s) system features the box-directed aggregation of multiple macrocycles, leading to generation of several stable species such as H4G (1a/ o-Box) and H5G (1a/ o-Box). Remarkably, a dimeric shish-kebab-like ring-in-rings superstructure H7G2 (1a/ o-Box) or H8G2 (1a/ p-Box) is formed from the coaxial stacking of two ring-in-rings units. The formation of such unique dimeric superstructures is attributed to the large π-surface of this 2D planar macrocycle and the conformational variation of both host and guest.