Competing Hydrogen-Bond Polarities in a Dynamic Oligourea Foldamer: A Molecular Spring Torsion Balance

J Am Chem Soc. 2018 Mar 14;140(10):3528-3531. doi: 10.1021/jacs.8b00567. Epub 2018 Mar 6.

Abstract

Symmetrical oligourea foldamers were made from meso cyclohexane-1,2-diamine and desymmetrised by incorporating terminal functional groups (carbamates, ureas or thioureas) with differing hydrogen-bonding capacities. Irrespective of solvent, the foldamers populate a dynamic equilibrium of two alternative screw-sense conformers whose relative population is determined by the competing hydrogen-bonding properties of the terminal groups, dictating the foldamer's global hydrogen-bond directionality. Intermolecular association of these dynamic foldamers with achiral anionic guests (acetate or phosphate, but not neutral hydrogen-bonding solvents) leads to inversion of the conformational preference, as strong intermolecular hydrogen bonding induces reorganization of the intramolecular hydrogen-bond network. The foldamers behave as a molecular torsion balance whose conformational preference is governed by competing hydrogen-bond pairing.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Hydrogen Bonding
  • Molecular Dynamics Simulation*
  • Urea / chemistry*

Substances

  • Urea