Metal-organic supramolecular cages can act as charged molecular containers that mediate reactions, mimic enzymatic catalysis, and selectively sequester chemicals. The hydration of these cages plays a crucial role in their interactions with other species (for example, substrates, counterions, and guest molecules). However, the interactions of water molecules and counterions are challenging to detect by standard analytical chemistry techniques, but can be detected with dielectric spectroscopy, specifically microwave microfluidics. Here, we use microwave microfluidics to measure the hydration and ion pairing of two metal-organic cage assemblies that are isostructural but have different overall anionic charge (12- for K12(Ga4L6), 8- for K8(Si4L6)).  We supplement our measurements with density functional theory calculations to compare binding site energies on model metal-organic cage vertices.  Unexpectedly, we find that the K8(Si4L6) cage is more strongly hydrated and forms a distinct ion pair species from the K12(Ga4L6) cage. Broadly, this work highlights the utility of microwave microfluidics to elucidate the consequences of charge states on metal-organic complexes in solution.<br/><br/>

Measuring ion-pairing and hydration in supramolecular cages with microwave microfluidics

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.