Self-assembled Co(II) and Co(III) [M2L3] helicates and [M4L6] tetrahedra from an unsymmetrical quaterpyridine ligand

In order to bind guest molecules with exquisite selectivity, biological host molecules often employ low symmetry binding pockets. The majority of metallosupramolecular assemblies, however, rely on symmetrical ligands to form high-symmetry assemblies that enclosing similarly symmetrical cavities. Here we employ an unsymmetrical quaterpyridine ligand in combination with cobalt(ii) to form a mixture of low-symmetry [M2L3] helicates and [M4L6] tetrahedra and their subsequent oxidation to Co(iii)-containing assemblies.