Tandem templating strategies facilitate the assembly of calix[8]arene-supported Ln 18 clusters.

Calix[ n ]arenes offer ideal chemical functionality through the polyphenolic lower rim to construct nano-sized coordination clusters with lanthanide (Ln) metal ions ( e.g. , NdIII10, GdIII8). However, the number of metal centers they can accommodate is still limited compared to that achievable with smaller ligands ( e.g. , GdIII140, GdIII104). Here, we exploit a combination of the "anion template strategy" and "templating ligands" to synthesise three highly symmetric ( D 3h , trigonal planar) LnIII18 (Ln = La, Nd, and Gd) systems, representing the largest calix[ n ]arene-based coordination clusters yet. The LnIII18 fragment is templated by a chloride anion located at the center of the cluster, wherefrom twelve μ 3 -OH - ligands bind 'internally' to the eighteen Ln III ions. 'Externally' the metallic skeleton is connected by p-tert -butylcalix[8]arene, oxo, chloro and carbonate ligands. The crystal packing in the lattice reveals large cylindrical channels of ∼26 Å in diameter, whose pore volume corresponds to ∼50% of the unit cell volume (using a 1.2 Å spherical probe radius). Magnetic measurements reveal the predominance of weak antiferromagnetic exchange in the Gd analog. Heat capacity data of GdIII18 reveal a high magnetic entropy with -Δ S m = 23.7 J K -1 kg -1 , indicating potential for engineering magnetic refrigerant materials with calix[8]arenes.