Self-assembly of trigonal prismatic M6(μ–L)9 coordination cages

The new ligand bis-bidentate ligand L, containing two pyrazolyl-pyridine chelating units connected to a 1,8-anthracene-diyl core via methylene spacers, reacts with Zn(II), Cd(II) and Cu(II) salts to form trigonal prismatic coordination cages [M6(μ–L)9]12+ in which a metal ion occupies each vertex and a bridging ligand spans each edge; the structure is stabilised by anions which occupy the central cavity and the gaps in the centres of the triangular faces, and also by extensive inter-ligand aromatic stacking between anthracenyl and pyrazolyl-pyridine groups.