Charge-assisted hydrogen bonds and weak intermolecular interactions as tools to fabricate complex supramolecular architectures

The rational design of synthetic supramolecular architectures based on well-defined structure-directing forces and hydrogen bonding is still a challenge. We present a supramolecular cage assembled through 72 hydrogen bonds which is constructed from two kinds of hexagonal molecular tiles forming a truncated octahedron, one of the thirteen Archimedean polyhedra (Science 2011, 333, 436). The framework displays an extraordinary ability to encapsulate a wide range of differently charged species, not observed otherwise. By the exploitation of the same kind of interactions, orientation of polyconjugated guest molecules is obtained in tunable host cavities. The framework host architectures can be controlled systematically in a manner that enables the regulation of the guest orientation and aggregation (J. Am. Chem. Soc. 2010, 132, 14603). The effects of the distinct packing motifs is manifested as bathochromic shifts in the absorption and emission spectra of the guests as interpreted by ab initio TDDFT calculations. Interestingly, through CH∙∙∙pi interactions, the molecular recognition of specific blocks of triblock copolymers by a host molecule promotes the formation of hierarchical periodic structures. The formation of the supramolecular architectures is followed by in situ synchrotron X-ray diffraction while the specific CH∙∙∙pi intermolecular interactions are highlighted by fast-1H MAS NMR and GIAO HF ab initio calculations (J. Am. Chem. Soc. 2011, 133, 8982). Moreover, weak intermolecular interactions play a key role in modulating the dynamics of molecular rotors in amphidynamic materials. Indeed, the precise engineering of highly-organized porous silica scaffolds supporting organic elements allows the fabrication of fast molecular rotors (k>108 Hz) entirely exposed to the guest molecules which act as regulators (Angew. Chemie Int. Ed. 2010, 49, 1760).