Supramolecular Anion Recognition

In collaboration with the Haley lab, we have developed a series of arylethynyl urea scaffolds for anion sensing. The appeal of this receptor design is the inherent fluorescence of the core and its modular construction allows for easy functionalization of the core and pendant arenes. A preorganized binding cavity formed by a rigid alkyne linkage between arene rings and urea-based hydrogen bond donors is the basis for reversible host-guest binding interactions. Previous studies have shown the receptor’s ability to selectively bind chloride upon protonation of a pyridine receptor, inducing a change in fluorescence. Current studies with this family of compounds include: fundamental studies of different supramolecular anion binding motifs, sensing biologically relevant anions in aqueous media, high-throughput array sensing, and designing new methods to selectively detect environmentally relevant anions.

Nanoclusters & Nanoparticles

Developing strategies to prepare inorganic clusters has attracted research interest due in part to the potential applications of these novel compounds. We have developed several a new synthetic methods for preparing discrete inorganic clusters, and we have used these processes to prepare the first crystalline example of tridecameric Group 13 clusters (Ga13, see figure). This synthetic route also yields the analogous tridecameric aluminum complex as well as mixed Ga/In and Al/In tridecameric clusters in preparative scales. We are currently exploring the formation mechanism of this series of clusters by studying their solution dynamics. This information could lead to both the identification of clusters in solution and a predictive strategy for new methods that will yield clusters composed of new metals. 

Main Group Supramolecular Chemistry

Applications in metal remediation, both environmental and medical, are envisioned by designing the ligands to target a specific toxic or hazardous metal ion. Here we are elaborating a design strategy for forming coordination capsules comprised of toxic metal ions or main group elements (such as arsenic, antimony and bismuth). We have shown that ligand H2L binds arsenic(III) within a very stable As2L3 cage. Surprisingly, two As2L2Cl2 macrocycles were also isolated as stable, kinetic intermediates in the reaction. Due to the dynamic covalent nature of the pnictogen-thiolate bond, these Group 15 capsules are observed to be highly reactive, allowing for transmetalation, conformational isomerism, heterometallic self assembly and interesting secondary bonding interactions. Furthermore, the novel cavity environments in these capsules will lead to unusual host-guest properties.
The process of surface modification allows us to combine the structural properties and advantages of mesoporous materials with the chemical functionality of organic compounds. This allows for a high surface area material that can remove contaminants from water via binding with the organic compound. For this application, their high degree of functionality and high-affinity surface chemistries permit a relatively small amount of material to effectively treat a large volume of water. Our goal is to explore surface chemistries that will allow for high performance sorbent materials which are regenerable or recyclable. We are approaching this goal by developing non-covalent, supramolecular surface modification techniques. Supramolecular attachment of organic molecules to surfaces allows us to avoid the necessity of optimizing the attachment for each class of organic molecules and avoids protection/de-protection procedures necessary to attach delicate or reactive functional groups. In this way, supramolecular modification processes reduce the costs of material research and development, as well as the costs of material production and use. This project is collaborative with Pacific Northwest National Lab (PNNL) and typically students working on this project complete an internship at PNNL. 

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