The first Ln-based cluster published was [Eu III 2(H2TBC [8])(dmf)5] (30) reported in 1987, made from the reaction of Eu(ClO4)3 and H8TBC [8] in a basic dmf solution (Fig. ). The two Eu III ions are bridged by two µ-O(Ph) atoms from the H2TBC [8] ligand and one µ-O(dmf) atom, affording a {Eu2(OR)3} core. The remaining six O(Ph) atoms on the calix [8]arene are monodentate, with two being protonated as evidenced by the significantly larger Eu-O bond lengths. The ligand adopts a double-cone conformation with near-twofold rotational symmetry. The Eu III ions are both eight coordinate and in (EuO8} bicapped trigonal prismatic geometries. The dimeric {Ln2} unit is extremely common in the coordination chemistry of TBC [8] with lanthanide ions, and indeed there are multiple isostructural [Ln III 2(H2TBC [8])(solvent)5] complexes reported which differ only in the coordinated solvent present (Ln = Eu, La, Pr, Lu, Tm; solvent = dmf, dmso; Fig. ). A related monomeric complex, [Eu III (H6TBC [8])(NO3)(dmf)4] (31; Fig. ) can be made from the reaction of Eu(NO3)3, H8TBC [8] and K2CO3 in a basic dmf solution at T = 60 °C. The doubly deprotonated H6TBC [8] ligand adopts a pleated-loop conformation, bonding to the Eu III ion in a bidentate coordination mode. The metal is eight coordinate and in a distorted {EuO8} square antiprismatic geometry, with the remaining coordination sites being filled with dmf molecules and a bidentate nitrate ion. A similar compound, [Gd III (H6TBC [8])Cl(dmso)4] (32; Fig. ), can be made via the reaction of H8TBC [8] with GdCl3•6H2O in a basic MeCN/dmso solution, followed by diffusion with hexane. The structure of 32 is essentially the same as that in 31 but with a single, monodentate Cl -ion replacing the bidentate NO3 -. The same paper also reported the synthesis of a number of Ln III complexes varying in nuclearity form Ln1-Ln7 from a series of related chemical reactions. Interestingly, in a number of experiments the same general [Ln III 2(H2TBC [8])(solvent)5] complex was obtained and the five new complexes discovered all contain a related {Ln2} moiety which is in fact a smaller fragment in the construction of frameworks generally based on octahedra. In each case the calix [8]arene adopts either a perfect or near-perfect double-cone conformation, but with significant differences in the degree of deprotonation. Reaction of H8TBC [8] with Ce(NO3)3•6H2O in a basic MeCN/dmf solution, followed by diffusion with hexane, affords the complex [Ce IV 4O2(H2TBC [8])2(dmf)4] (33; Fig. ). At the centre of the molecule lies a non-planar/bowl-shaped {Ce4O2} butterfly. The Ce IV ions are all seven-coordinate and in distorted {CeO7} pentagonal bipyramidal in geometries. Each H2TBC [8] ligand exists as the hexa-anion, H2TBC [8], with two intra-molecular H-bonds between neighbouring O(Ph) atoms per calix [8]arene molecule, and bridges three Ce IV ions across one side of the butterfly. Four ligated dmf molecules complete the Ce IV coordination spheres, occupying the cavities generated by each of the H2TBC [8] molecules.