Systematic experimental charge density analysis of anion receptor complexes.

The first systematic electronic resolution study of a series of urea-based anion receptor complexes is presented. The hydrogen bonding in these multi-component systems was fully characterised using Bader's Quantum Theory of Atoms In Molecules (QTAIM) with the strength of the various N-H···anion hydrogen bonds quantified and the individual contributions of different intermolecular forces to the overall receptor: anion interaction derived by comparison of the charge densities in the related complexes. The strength of the N-Hanion hydrogen bonds was correlated to the basicity of the anion and related to the structure of the receptors.