title: Solute-solvent contact by intermolecular cross relaxation. I. The nature of the water-hydrophobic interface.
abstract: Intermolecular cross-relaxation rates between solute and solvent were measured by {1H} 19F nuclear magnetic resonance experiments in aqueous molecular solutions of ammonium perfluoro-octanoate and sodium trifluoroacetate. The experiments performed at three different magnetic fields provide frequency-dependent cross-relaxation rates which demonstrate clearly the lack of extreme narrowing for nuclear spin relaxation by diffusionally modulated intermolecular interactions. Supplemented by suitable intramolecular cross-relaxation, longitudinal relaxation, and self-diffusion data, the obtained cross-relaxation rates are evaluated within the framework of recent relaxation models and provide information about the hydrophobic hydration. In particular, water dynamics around the trifluoromethyl group in ammonium perfluoro-octanoate are more retarded than that in the smaller trifluoroacetate.
authors.affiliation: Division of Physical Chemistry and Industrial NMR Center, Department of Chemistry, Royal Institute of Technology, SE-10044 Stockholm, Sweden.
authors.forename: Lars
authors.initials: L
authors.lastname: Nordstierna
authors.forename: Pavel V
authors.initials: PV
authors.lastname: Yushmanov
authors.forename: István
authors.initials: I
authors.lastname: Furó