Sulfated prism[6]arene binds one guest internally and one guest externally

We report the synthesis of sulfated prism[6]arene (Pr[6]AS) by reaction of (HO) 12 Pr[6] with SO 3 ·pyridine in 35% yield. Pr[6]AS has very good solubility in water (>30 mM) and does not undergo self-association according to 1 H NMR dilution experiments. Qualitative 1 H 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·guest 2 ) with hydrophobic ammonium ions in phosphate buffered saline with β-values ( K a1 × K a2 ) values up to 6.84 × 10 13 M −2 . Molecular dynamics simulations show that Pr[6]AS firmly binds one guest ( 6q , Me 4 Bipip) within its cavity and a second guest ( 6q , Me 4 Bipip) 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 H 2 O 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 H 2 O 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 the design of high molecularity complexes.