- University Distinguished Professor
Expertise and Current Research ActivityChemists’ ability to manipulate molecules to work for society is only limited by their understanding of how various molecules and ions interact with each other. Our research uses host-guest chemistry to target molecules and ions of biological and environmental interest, for selective sensing and recognition such as mustard contaminants in the air, as well as for separations, such as in removing contaminating species from groundwater and other sources like the sludge in the huge tanks at nuclear waste sites.Host-guest chemistry is a branch of science where chemists use their knowledge of the structure and reaction of molecules to mimic how proteins and enzymes and proteins function in biological systems. Our recent focus has been on designing molecules that are capable of capturing two specific classes of guests, the chemical mustards and negatively charged ions (anions), both of which have significant environmental and biological impacts. The chemical mustards, highly toxic blistering agents, were first used in World War I in chemical warfare. However, they have also shown potential as chemotherapeutic agents.The most famous is the mustard gas, its name coined as a result of its mustard-like smell. In our research we design molecules that will bind and detoxify this noxious chemical, for applications in detection and in decommissioning. While the chemical mustards are neutral molecules, our other target species are charged species (ions). Ions are of special interest because of their importance in life’s processes, medicine, industry, and the environment.For example, fluoride can be a contaminant of ground water, causing a mottling of teeth known as fluorosis, or it can help fight tooth decay in smaller doses. Another well-known ion is Roundup®, a broad-spectrum, highly effective herbicide, which can potentially contaminate groundwaters such as lakes, streams and rivers.As part of our research program, we collaborate with researchers in Spain and Italy, as well as at Oak Ridge National Laboratory. I am also one of the co-editors of Anion Coordination Chemistry, the second edition of Supramolecular Chemistry of Anions, both published by Wiley-VCH in 2012 and 1997, respectively.
The design and synthesis of organized molecular frameworks as selective receptors for anions and as ligands for transition metal ions are the primary goals of our research program. Our interest in these areas stems from potential environmental and biological applications in sensing, separations, and catalysis. We also seek to examine the similarities (and differences) between anion/supramolecular coordination chemistry and traditional transition metal coordination chemistry. In this endeavor we are exploring the same ligand frameworks as both anion and transition metal ligands, involving hydrogen bonding and pi-pi stacking interactions for anion complexes, and coordinate covalent (or dative) bonds for transition metal complexes. We especially focus on solid state and solution structural influences as well as the kinetic and thermodynamic properties of ligands and the effects on the physical and chemical properties of complexes. A key focus is on a comparison of the influence of the chelate, macrocyclic, and cryptate effects on binding and thermodynamics in these complexes.