Abstract
In the biomimetic context, many studies have evidenced the importance of the 1(st) and 2(nd) coordination sphere of a metal ion for controlling its properties. Here, we propose to evaluate a yet poorly explored aspect, which is the nature of the cavity that surrounds the metal labile site. Three calix[6]arene-based aza-ligands are compared, that differ only by the nature of cavity walls, anisole, phenol or quinone (L(OMe) , L(OH) and L(Q) ). Monitoring ligand exchange of their Zn(II) complexes evidenced important differences in the metal ion relative affinities for nitriles, halides or carboxylates. It also showed a possible sharp kinetic control on both, metal ion binding and ligand exchange. Hence, this study supports the observations reported on biological systems, highlighting that the substitution of an amino-acid residue of the enzyme active site, at remote distance of the metal ion, can have strong impacts on metal ion lability, substrate/product exchange or selectivity.