title: Molecular tweezer and clip in aqueous solution: unexpected self-assembly, powerful host-guest complex formation, quantum chemical 1H NMR shift calculation.
abstract: The newly prepared water-soluble naphthalene tweezer 2a and anthracene clip 4a (substituted both with lithium methanephosphonate groups in the central spacer unit) undergo an unexpected self-assembly in aqueous solution. The highly ordered intertwined structures of the self-assembled dimers [2a]2 and [4a]2 were elucidated by quantum chemical 1H NMR shift calculations. 2a and 4a form extremely stable host-guest complexes with N-methylnicotinamide 8 in methanol and water as well. According to the thermodynamic parameters determined by 1H NMR titration experiments at various temperatures the self-assembly of 2a and 4a and their strong binding to NMNA 8 observed in aqueous solution are enthalpy driven (DeltaH << 0); the enthalpic driving force is partially compensated by an unfavorable entropy (TDeltaS < 0). Self-assembly and the host-guest binding are therefore beautiful examples of the nonclassical hydrophobic effect.
authors.affiliation: Institut für Organische Chemie der Universität Duisburg-Essen, 45117 Essen, Germany. frank.klaerner@uni-essen.de
authors.forename: Frank-Gerrit
authors.initials: FG
authors.lastname: Klärner
authors.forename: Björn
authors.initials: B
authors.lastname: Kahlert
authors.forename: Anke
authors.initials: A
authors.lastname: Nellesen
authors.forename: Jan
authors.initials: J
authors.lastname: Zienau
authors.forename: Christian
authors.initials: C
authors.lastname: Ochsenfeld
authors.forename: Thomas
authors.initials: T
authors.lastname: Schrader