Dynamic metallo-supramolecular oligomers stabilized by Cucurbit[8]uril connectors: self-assembly applied to combinatorial chemistry

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With the support of the Macromolecular, Supramolecular and Nanochemistry (MSN) program of the NSF Division of Chemistry, Prof. Masson investigates the recognition properties of water soluble metal-ligand complexes towards CB[n] and develops dynamic combinatorial approaches to preparing dynamic oligomers and polymers. Synthetic polymers are found in most objects used in everyday life. Polymers that spontaneously adjust their composition depending on their environment in water are of particular interest to Professor Eric Masson at Ohio University. His research group studies the formation and properties of a novel type of dynamic polymers in which the interchangeable building blocks are tied to one another with a pumpkin-shaped, hollow molecular ring called cucurbit[8]uril (CB[8]). The project has potential applications in biochemistry, as the dynamic polymers can interact with medically or biologically relevant materials such as proteins and cells, and in analytical chemistry, as the polymers can be used as sensors in quality control and drug detection applications. This project is multidisciplinary, and provides training to undergraduate and graduate students with a broad range of interests and talents, from organic synthesis, to biochemistry and statistical analysis. In addition, students are involved in the upgrade of an organic synthesis board game created by Professor Masson for computer tablets. The building blocks of the dynamic oligomers targeted herein are metal-terpyridine complexes linked to CB[8]-binding units. The terpyridine ligands bear phenyl or naphthyl groups at the 4'-position to promote binding in the CB[8] ring. The terpyridine ligands are also functionalized with bio-inspired side chains (based mostly on amino acid residues) at the 4- and 4"-positions for interactions with the outer wall of CB[8] and for target recognition. The metal-ligand complexes are connected non-covalently via binding to the CB[8] rings. The outer wall of CB[8] participates de facto in the target recognition process once the metal-ligand/CB[8] oligomers are formed. This project involves (1) the preparation of a library of metal-ligand complexes (such as iron(II)-, ruthenium(II)- and iridium(III)-terpyridine) with a variety of pendent groups; (2) the assessment of their recognition properties towards CB[n]s and the interactions between the pendent groups with the outer convex surface of CB[n]s; and (3) the preparation and characterization of the metal-ligand/CB[8] dynamic oligomers in the absence and presence of biologically relevant targets.