Selective Metal‐ion Complexation of a Biomimetic Calix[6]arene Funnel Cavity Functionalized with Phenol or Quinone

• Published in: Chemistry : a European journal 2023-01, Vol.29 (5), p.e202202934-n/a
• Main Authors: Aoun, Pamela, Nyssen, Nicolas, Richard, Sarah, Zhurkin, Fedor, Jabin, Ivan, Colasson, Benoit, Reinaud, Olivia
• Format: Article
• Language: English
• Subjects: biomimetic complexes; Biomimetics; calixarene; Calixarenes - chemistry; Chemical Sciences; host-guest; Ligands; Metals; Phenol; Phenols - chemistry; Quinones; supramolecular; zinc
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.202202934

In the biomimetic context, many studies have evidenced the importance of the 1st and 2nd 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 (LOMe, LOH and LQ). Monitoring ligand exchange of their ZnII 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. The calixarene core allows the introduction of functional groups at remote distance from the metal ion, but in the vicinity of its labile site. Introducing a phenol or quinone moiety in the calix core, in place of anisole, drastically changes not only thermodynamics but also kinetics of metal ion and guest‐ligand binding, while the first coordination sphere is not affected.