Nano-Containers for Novel Separations and Reactions

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With this award, the Macromolecular, Supramolecular and Nanochemistry Program in the Division of Chemistry is supporting Professor Bruce Gibb of Tulane University to develop new 'nano-containers' for applications in both chemical reactions and chemical separations. In the everyday world containers are utilized to store, transport, and separate items. Chemists also use containers (reaction flasks) to form new matter; mixing A and B gives new compound C; a new pharmaceutical, perhaps, a new coating material to prevent rusting in bridges and other infrastructure, or perhaps a new molecule for the next generation flat-screen OLED television. This project concerns very small containers. These nano-containers spontaneously form in water and possess inner-spaces approximately one-billionth the size of a small dust particle. As a result, when even the smallest of molecules is stored in these containers they constantly bump into the sides of the vessel. This leads to some very unusual chemical properties, of which two are being investigated: 1) Nano-containment can lead to new chemical reactivity, and consequently this program investigates some of the reactions that can occur within these containers to evaluate their overall properties; 2) New separation protocols are also possible, and with this in mind the purification of industrially important chemicals from complex mixtures is being investigated. Both the identification of new chemical reactions and the development of new, non-energy intensive separations have the potential for broader scientific impact across the chemical enterprise. This program of research will also provide research training for undergraduate and graduate students in both analytical and synthetic chemistry. This proposal has two related overall goals. Both concern the selective complexation of guest molecules within well-defined, nano-capsules formed by water-soluble cavitands. The first aim is to examine the ability of this family of hosts to act as phase-transfer catalysts for new and unusual chemical conversions. Early work has identified that these hosts bind reactive anions, including inorganic anions, and that these can be co-encapsulated with organic guests. Trapped within the yocto-liter volumes formed by these dimerized hosts, the two guests experience high effective molarity, relative to each other. Building on these points, the proposed studies utilize NMR and GC-MS to investigate the co-encapsulation of a range of reagents and substrates and hence bring about efficient, regioselective conversion processes that are catalytic in host. The second aim of this proposal is to use the observed selective guest-binding properties of these hosts to bring about the separation of complex mixtures of terpenoids and constitutionally isomeric hydrocarbons. The proposed plans examine the hosts as shape-selective phase-transfer catalysts in U- and W-tube experiments. NMR and GC-MS experiments are utilized to examine the performance of each host carrier for the different cases studied.