Development of supramolecular structure through alkylation of pendant pyridyl functionality

The complex 1²⁺ which has two pendant 4-pyridyl substituents may be viewed as a metal-containing analogue of 4,4′-bipyridine. The complex undergoes N-alkylation reactions with a variety of alkylating agents to give more highly functionalised tetracationic complexes which may be termed metalloviologens by analogy with viologens. These complexes may also be prepared by alkylation of the free ligands and subsequent coordination of the pendant quaternised ligand. Structural studies have established that the N-alkylated complexes possess the correct spatial characteristics for the preparation of metallocycles analogous to known cyclic bis(4,4′-bipyridinium) species which possess useful molecular recognition properties.