Host–Host Interactions Control Self‐assembly and Switching of Triple and Double Decker Stacks of Tricarbazole Macrocycles Co‐assembled with anti‐Electrostatic Bisulfate Dimers

Hierarchical assembly provides a route to complex architectures when using building blocks with strong and structurally well‐defined recognition elements. These rules are traditionally expressed using cationic templates with reliable metal‐ligand bonding but use of anions is rare on account of weak anion–host contacts. We investigate an approach that relies on host–host interactions to fortify assemblies formed between bisulfate anion dimers, [HSO4⋅⋅⋅HSO4] 2− , and shape‐persistent macrocycles called tricarbazole triazolophanes. These macrocycles have significant self‐association. In chloroform, they form high fidelity, triple‐decker stacks with bisulfate dimers. The strength of host–host interactions allows for preferential formation of the 3:2 tricarb:bisulfate architecture over an ion‐paired architecture seen with analogous macrocycles with much weaker self‐association. Solvent was expected and found to tune host–host contacts enabling formation of a 2:2 complex and solvent‐driven switching between triple‐ and double‐stacked structures. Crystallography of the 2:2:2 complex supports the idea that significant host–host interactions with tricarb arises from dipole‐stabilized π‐stacking. Computational studies were also conducted further highlighting the importance of host–host interactions in stacked complexes of tricarb. These findings unambiguously verify the importance of host–host interactions in the assembly and stability of discrete, responsive anion‐templated architectures.