Electronic Supporting Data: Sulfated Prism[6]arene Binds One Guest Internally and One Guest Externally

Abstract

We report the synthesis of sulfated prism[6]arene (Pr[6]AS) by reaction of (HO)12Pr[6] with SO3•pyridine in 35% yield. Pr[6]AS has very good solubility in water (>30 mM) and does not undergo self-association according to 1H NMR dilution experiments. Qualitative 1H NMR investigations show that guest resonances shift dramatically upfield and become significantly broadened upon complexation with Pr[6]AS. Isothermal titration calorimetry (ITC) experiments show that Pr[6]AS forms ternary complexes (Pr[6]AS•guest2) with hydrophobic ammonium ions in phosphate buffered saline with -values (Ka1 x Ka2) values up to 6.84 x 1013 M-2. Molecular dynamics simulations show that Pr[6]AS firmly binds one guest (6q, Me4Bipip) within its cavity and a second guest (6q, Me4Bipip) on the convex region of Pr[6]AS in close proximity to the externally directed sulfate substituents. Uncomplexed Pr[6]AS holds 7.6 ± 1.9 H2O and one Na+ ion within its cavity. Formation of the 1:1 and 1:2 Pr[6]AS-6q complexes results in expulsion of the Na+ ion and approximately five of the solvating H2O molecules. Intriguingly, the combination of larger naphthalene walls and sulfate ionic groups that are conformationally restricted creates a secondary guest binding site on the exterior of Pr[6]AS which suggests a route toward design of high molecularity complexes.