Measurements of weak halogen bond donor abilities with tridentate anion receptors.

The chelate effect of a tridentate receptor is exploited to determine halogen bonding association constants that vary by several orders of magnitude, including interactions of weak donors for which thermodynamic data were not previously available. Free energy relationships with computed and experimental properties hold over this wide range of donors. The strengths of iodine- and bromine-based halogen bonds, CH-anion and anion-arene interactions are compared.