As part of an ongoing investigation of the factors influencing metal ion recognition, we have investigated structure/function relationships involving the metal-ion binding by three new N-benzyl-substituted, 15- and 16-membered, macrocyclic ligands incorporating N2O3- and N3O3-donor sets (with the N3O3-systeM consisting of a N2O3-macrocyclic ring with an attached CH2CH2NCH2C6H5 pendant arm). Selected solid complexes of the latter ligand were isolated and the X-ray structures of individual Ni(II) and Ag(I) complexes were obtained.Where solubility permitted, potentiometric titration studies in 95% methanol were employed to investigate the binding affinities of all three ligand derivatives towards Co(II), Ni(II), Cu(II), Zn(II), Cd(II), Ag(I) and Pb(II). The 15-membered N2O3-ring was found to be selective for Ag(I) over the other six metals investigated, including Cu(II). However, the presence of a further nitrogen donor in the form of the pendant benzylamine functionality in the N3O3-donor system results in an increase in its binding affinity for Ag(I) but an even greater increase occurs for Cu(II). As a consequence, the latter ion is now more strongly bound than Ag(I). The factors influencing these respective selectivities are discussed.
|Journal||Journal of Inclusion Phenomena and Macrocyclic Chemistry|
|Publication status||Published - 2001|