UC Riverside

Metal assisted self-assembly is a useful tool for the creation of supramolecular structures that can function as molecular switches, cavity containing hosts, and sensors. A wide variety of unfunctionalized supramolecular cages bearing large internal cavities have been synthesized to date, and these hosts are able to effectively bind substrates, but molecular hosts containing internal functionalization are still rare. The use of symmetrical, aromatic ligands is often necessary to control the assembly process, and the presence of reactive functional groups can complicate or interfere with the synthesis. To overcome these challenges and develop useful internally functionalized complexes, new methods for precisely controlling the assembly process must be investigated.

This work explores various methods of controlling the assembly process, with an overarching goal of creating useful endohedrally functionalized species for molecular recognition and biomimetic catalysis. High fidelity narcissistic self-sorting of near identical ligands leads to selective and sequential formation of specific homocomplexes from multicomponent reaction mixtures and provided insight into what traits govern the favorability of certain assemblies. Small variations to the electronic nature of the coordinating motif were found to increase the thermodynamic stability or the formation rate, and these simple modifications can be used to tune the properties of the final products. Post assembly modifications were performed and lead to the discovery of a structural switch between a polymeric aggregate and a discrete cage. This method was also utilized to oxidize doubly benzylic methylene units in a stereoselective manner to form unusual products. The post-assembly oxidation is directed by the structure of the cages themselves, involves catalytic metal arising from the reversible dissociation of the chelating groups, and occurs in high yield without degradation of the structural iron atoms. In addition, a large FeII-iminopyridine cage was synthesized bearing twelve internal carboxylic acid groups and effected a 1000-fold rate enhancement in the hydrolysis of aromatic acetals. The compartmentalized nature of the acid groups allowed a cage-to-cage tandem reaction in the presence of sensitive complexes, whereas control acid catalysts were too weak to allow for transformation or caused decomposition of the complexes.