Macrocyclic ligand design.: Structure-function relationships involving the interaction of pyridinyl-containing, oxygen-nitrogen donor macrocycles with selected transition and post transition metal ions on progressive N-benzylation of their secondary amines

Structure-function relationships underlying the interaction of progressively N-benzylated N4O2-donor macrocycles with cobalt(II), nickel(II), copper(II), zinc(II), cadmium(II), silver(I) and lead(II) have been probed using a range of techniques that include X-ray diffraction, DFT computations, solvent extraction, potentiometric stability constant determinations and competitive membrane transport experiments. Collectively, the results indicate that N-benzylation of the secondary amine donor groups of the parent macrocyclic ring results in an enhanced tendency towards selectivity for silver(I) relative to the other six metals investigated. The observed behaviour serves as additional exemplification of the previously proposed concept of selective 'detuning' as a mechanism for metal ion discrimination.