Inspired by enzymatic catalysis in biological systems, the field of supramolecular chemistry has strived to understand the roles of specific features observed in enzymatic active sites on the reaction rates and selectivities achieved by enzymes. The microenvironments created by the cavities of a supramolecular assemblies have been shown to facilitate selective host–guest interactions, rendering enzyme-like rate accelerations of divergent reaction pathways that would otherwise be impossible in bulk solution. One such supramolecular structure is the Ga4L612- tetrahedron developed by the group, which self assembles readily in polar solvents. By treating this assembly as a simplified enzyme, we have been able to study and identify the origins of rate enhancements in enzymatic catalysis. These experimental analyses, however, have remained largely qualitative, relying on theoretical calculations to quantify relative contributions of variables such as size and charge of the microenvironment. To address this issue and to further understand the driving forces behind enzymatic catalysis, we have synthesized a novel Si4L68- supramolecular assembly—an isostructural analogue to the Ga4L6 tetrahedron but with a reduced charge. Side-by-side kinetic comparison studies were conducted with this Si (IV) host on two mechanistically distinct Ga4L6-catalyzed reactions, enabling us to experimentally investigate the specific role of charge in each of these systems. This is one of the first examples in which a supramolecular assembly, tunable in charge, functions as a mechanistic probe for the reactions that it catalyzes.

Supramolecular assemblies as a mechanistic probe: Formation and catalysis of a Si4L6 host

255th National Meeting (2018)

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