Mercury-based anion receptors

The first literature example of a mercury based receptor (32) for anions was analogous to the chelating boron receptor discussed earlier. The crystal structure indicated that two molecules of Compound 32 asociate with one chloride ion, which sits in a four-coordinate binding site. Solution studies, however, gave results indicative of 1 l binding for halide anions (94, 95). This simple... 

The hosts outlined above generally utilize their metal centers to provide interactions with anions. The orbital overlap between unfilled heteroelement orbitals and filled anion orbitals yields bonding interactions. In the case of the mercury based receptors, the role of the metal atoms is partly structural, with their sp hybridization linear geometry specifically yielding large macrocyclic cavities of suitable diameters for anion encapsulation. The metal atoms have often been functionally used as an NMR handle on the anion coordination process. 

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