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