We report an investigation of the complexation between a water soluble pillararene host (WP6) and a panel of hydrophobic cationic guests (G1 - G20) by a combination of 1 H NMR spectroscopy and isothermal titration calorimetry in phosphate buffered saline. We find that WP6 forms 1:1 complexes with K a values in the 10 4 - 10 9 M -1 range driven by favorable enthalpic contributions. This thermodynamic dataset serves as blinded data for the SAMPL9 challenge.