A new allosteric bis crown ether ligand that displays negative binding co-operativity of the diquat dication by the complexation of a transition metal guest

The synthesis of a new allosteric 2,2′-bipyridyl bis crown ether ligand (3) that binds the diquat dication is described; chelation of a transition metal at the allosteric bipyridyl site forces the bipyridyl function towards coplanarity, restricting the conformational freedom of the two benzo-15-crown-5 moieties in such a way as to disfavour the subsequent binding of diquat.