Dynamics of Hydrogen-Bonded Supramolecular Assemblies

We are studying the dynamics of supramolecular assemblies, collections of molecules that adopt a particular structure due to a large number of (relatively) weak interactions.  In particular, we are interested in assemblies that are held together by hydrogen bonds and that can encapsulate other molecules in solution.  Such "host-guest" supramolecular assemblies hold significant promise as potential catalyst structures:  It has been demonstrated that assemblies can encapsulate reactants, lower the free energy of activation for a desired chemical transformation (with or without an additional catalyst), and release the nascent products.  A key challenge is that, while the encapsulation can provide benefits in selectivity, these assemblies generally exhibit slower kinetics.  This is usually attributed to the slow process of encapsulating the reactants and releasing the products.  Unfortunately the mechanism for these capture/release processes are not understood and thus it is difficult to know how to accelerate them.  This is a focus of our current work.  

We are particularly interested in the behavior of hexameric resorcin[4]arene assemblies, illustrated above, that are composed of six resorin[4]arene monomers and eight water molecules in wet chloroform. They assemble into a roughly spherical cavity held together by 60 hydrogen bonds.

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