The remarkable influence of N,O-ligands in the assembly of a bis-calix[4]arene-supported [Mn^IV₂Mn^III₁₀Mn^II₈] cluster

Calix[4]arenes are versatile ligands, capable of supporting the formation of a wide variety of polymetallic clusters comprising 3d, 4f or 3d–4f metal ions. Calixarene-based metal ion fragments act as both bridging and structure capping moieties in these systems, and this behaviour is systematically extended upon moving to bis-calix[4]arene, a relatively new ligand in which two calix[4]arenes are tethered at the methylene bridge position. N,O-Ligands greatly influence cluster formation with bis-calix[4]arene, affording a remarkable mixed-valence [MnIV2MnIII10MnII8] cluster that displays coordination chemistry typical of each ligand type, but also new structure capping behaviour for the latter.