(715g) Solvent-Mediated Interactions Between Supramolecular Hosts and Hydrophobic Guests

Cavitands and nanotubes possess unique supramolecular recognition that can impact the energies and conformations of the encapsulated hydrophobic guests. Using molecular simulations we investigate guest-host interactions between hydrophobic guests with cavitand and nanotube hosts. In preliminary studies we have examined the selectivity of deep-cavity cavitands with simple Lennard-Jones (LJ) type guests in water as a function of LJ diameter and well-depth. We observe that for smallest size guest used, the guest occupancy inside host increases with increase in interaction, whereas for larger size guests the variation in interaction has no influence on the occupancy. We further evaluate potential of mean force (PMF) between adamantane and cavitand using umbrella sampling technique, which illustrates the strong binding interaction between them. In a second study we have examined trans-to-gauche conformational change for a range of linear alkanes confined within a nanotube. The estimated dihedral angle distributions show a significant rise in the gauche conformations of encapsulated guests, indicating the helical folding of alkanes within nanotube. We also estimate the PMFs between alkanes and nanotube in various solvents and deconvolute it into its direct host-guest and indirect solvent-mediated contributions. Overall our results indicate that these supramolecular hosts and hydrophobic guests are highly interactive.