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Diffusion of a Highly Charged Supramolecular Assembly: Direct Observation of Ion Association in Water1

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posted on 2008-03-03, 00:00 authored by Michael D. Pluth, Bryan E. F. Tiedemann, Herman van Halbeek, Rudi Nunlist, Kenneth N. Raymond
The diffusion coefficient of the self-assembled supramolecular cluster [Ga4L6]12− depends on the cationic counterions in solution. Diffusion coefficients were determined using the pulsed-gradient spin–echo 1H NMR method and fit using nonlinear least-squares refinement. Saturation studies revealed a small number of ion-association sites on the exterior of the assembly and the direct observation of ion association in water. The addition of excess alkali-metal cations displaces the ion-associated hydrophobic tetraalkylammonium cations. Comparisons between tetraethyl- and tetrapropylammonium show a preference for ion association with the more hydrophobic cation.

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