Metal complexes of azacrown ethers in molecular recognition and catalysis

Reversible coordination of ligands or substrates with Lewis-basic groups to Lewis-acidic metal ion binding sites can provide the binding enthalpy and selectivity necessary for molecular recognition or catalysis. Metal complexes of functionalised azamacrocycles have proven to be particularly useful for this purpose. This review summarises the properties and applications of some recently published compounds of this kind, giving typical examples, but no comprehensive coverage of the field. With focus on molecular recognition, the binding of inorganic and organic anions to metal complex binding sites, changes of anion properties induced by the binding and the interaction of metal complexes with the polyanion DNA are discussed. The second part of the review focuses on catalysis mediated by azamacrocyclic Lewis-acidic metal binding sites leading to ester hydrolysis, redox catalysis or polymerisation.