The combination of six Cu(II) centres with four cyclotricatechylene (ctc⁶⁻) ligands generates large (Cu₆ctc₄)¹²⁻ cages with the topology of the tetrahedron. The anionic tetrahedral cages are cemented together, triangular face to triangular face, by Na⁺ cations together with water molecules to generate a highly symmetric diamond-like assembly (space group Fd-3m, the same as that of diamond itself) whose adamantane-like units have an iodide ion at the centre of every cyclohexane-like face.