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Quantifying the Effect of Guest Binding on Host Environment



Angela Stelson, Zack Fishman, Jacob Pawlik, Gosia Musial, Jim Booth, Chris Long, Kathleen Schwarz, Nate Orloff, Hugh Ryan, Angela Grommet, Jonathan Nitschke, Felix Rizzuto


The environment around a host-guest complex is defined by of intermolecular interactions between solvent molecules and counter ions. These interactions govern both the solubility of these complexes and the rates of reactions confined within them11. Such noncovalent2 interactions between solvent molecules and ions are challenging to detect by standard analytical chemistry techniques. We use microwave microfluidic spectroscopy to quantify the hydration and ion pairing of a FeII4L4 coordination cage with a set of guest molecules having widely varying physicochemical properties3,4. Significantly, we observed that the environment around a host-guest complex changes depending on the identity of the encapsulated guest. The impact of different guest properties on host ion pairing and hydration was determined through microwave microfluidic measurements paired with principal component analysis . This analysis showed that introducing guest molecules into solution displaced counterions that were bound to the cage, and the water solubility of the guest has the greatest impact on the solvent and ion-pairing dynamics surrounding the host. We also observed that cage-counterion pairing is well-described by a single ion-pairing type, with a one-step reaction model independent of the type of cargo, and that the ion-pairing association constant is reduced for cargo with higher water solubility. Looking beyond this study, microwave microfluidics elucidates structure-property relationships that connect the host interior cavity to its external environment, and these measurements enable improved design of host-guest systems for chemical separations, catalysis, and more.
Journal of the American Chemical Society


Microwave microfluidics, Metal-organics, coordination cages, ion-pairing, solvation


Stelson, A. , Fishman, Z. , Pawlik, J. , Musial, G. , Booth, J. , Long, C. , Schwarz, K. , Orloff, N. , Ryan, H. , Grommet, A. , Nitschke, J. and Rizzuto, F. (2023), Quantifying the Effect of Guest Binding on Host Environment, Journal of the American Chemical Society, [online],, (Accessed May 24, 2024)


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Created August 29, 2023, Updated September 20, 2023