(746a) Designer Wetting of Supramolecular Hosts

Deep cavity cavitands are water soluble supramolecular host species that possess a ~1 nm wide and deep hydrophobic pocket that readily bind nonpolar guests. We present a molecular simulation study and experimental results for the affinity of water for deep cavity cavitand host pockets. Specifically, we consider the cavitand octa-acid (OA) and its derivatives, tetra-endo-methyl-octa-acid (TEMOA) and tetra-exo-methyl-octa-acid (TEXMOA). These desrivative differ from OA by the placement and orientation of four methyl units about the host pocket. We demonstrate that while water readily wets the pockets of OA and TEXMOA, when the methyl units are oriented towards the pocket for TEMOA water dewets the pocket. This dewetting event is observed from molecular simulations and is confirmed by high precision densimetry experiments. We subsequently consider the impact of pocket dewetting on the thermodynamics of guest binding, and the potential implications for utilizing dry states to moderate hydrophobic interactions.