Unveiling host-guest-solvent interactions in solution by identifying highly unstable host-guest configurations in thermal non-equilibrium gas phase

초록

We propose a novel scheme of examining the host-guest-solvent interactions in solution from their gas phase structures. By adopting the permethylated beta-cyclodextrin (perm beta-CD)-protonated L-Lysine non-covalent complex as a prototypical system, we present the infrared multiple photon dissociation (IRMPD) spectrum of the gas phase complex produced by electrospray ionization technique. In order to elucidate the structure of perm beta-CD)/LysH(+) complex in the gas phase, we carry out quantum chemical calculations to assign the two strong peaks at 3,340 and 3,560 cm(-1) in the IRMPD spectrum, finding that the carboxyl forms loose hydrogen bonding with the perm beta-CD, whereas the ammonium group of L-Lysine is away from the perm beta-CD unit. By simulating the structures of perm beta-CD/H+/L-Lysine complex in solution using the supramolecule/continuum model, we find that the extremely unstable gas phase structure corresponds to the most stable conformer in solution.

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