Architectural Design of Supramolecular Hosts from Simple Amide/Amine Building Blocks

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Award in the Inorganic, Bioinorganic and Organometallic Chemistry program supports Professor Kristin Bowman-James to explore: anion binding, to evaluate the role of lone protons in chemical processes, and the binding and manipulation of neutral triatomic gases. A systematic approach is used by linking a series of similar amide/amine-based hydrogen-bond donor building blocks to give hosts with increasing complexity and dimensionality, and differing degrees of rigidity. The five specific goals are: 1) Simple amide/amine containing hosts will be strategically modified to probe the addition of more hydrogen bonding sites as well as redox switches, the latter using pendant sulfhydryl groups. 2) Structural data on binding of linear and V-shaped anions will be used to expand the project to neutral gases, specifically CO2, N2O, and SO2. Both traditional hydrogen bonding strategies will be used as well as dynamic covalent chemistry (DCC), the formation of covalent bonds that can be readily broken. 3) Complex cyclophane-capped multicycles will be explored as hosts for larger polyanionic guests, including metallates, polyphosphates, nucleotides, and carboxylates. These hosts will provide more rigid architectures than earlier ligands. 4) The prototype phenyl host caps will be replaced by triazine, pyrazine and naphthalene to examine a) the influence of heteroatoms in the preorganization of the side chains and stacking distances, and b) the use of naphthalene to circumvent an acid decomposition of the host with four linkers (tetrad) as well as undesirable intramolecular NHC hydrogen bonds. 5) Structural data indicating that a lone proton could play a role in shaping the conformations of molecules will be pursued to assess the generality of this phenomenon. The goal of this work is to design more complex hosts that will show high affinity for larger and more challenging guests with two targets being neutral gases and single protons. The broader impacts are the educational component that spans students from undergraduate to postdoctoral status, and outreach that includes women and underrepresented minorities. The societal impacts are in understanding not only the complex chemistry involved in anion recognition but also the more elusive targets of neutral gas recognition and the role that lone protons could play in supramolecular and biological chemistry.