There is a single family of isostructural Cr-based clusters of formula [Cr III Ln III 6O2(OH)(TBC [8])2(H2O)4(dmf)5(MeOH)2] (Ln = Gd (29a), Tb (29b), Dy (29c), Tm (29d); Fig. ), the general metallic skeleton of which describes a capped distorted octahedron. The {Ln5Cr} octahedron is bridged internally via two µ4-O 2-ions; an alternative description of the core is therefore of two edge-sharing {Ln4O}/{Ln3CrO} tetrahedra. The remaining Ln ion caps a {Ln2Cr} face, being coordinated to it through the presence of three µ3-bridging O-atoms derived from H2O molecules. The sole µ-bridging OH -ion spans a {Ln2} edge of the octahedron. Both fully deprotonated TBC [8] ligands adopt the double-cone conformation sandwiching the inorganic core of the molecule, lying perpendicular with respect to each other. They coordinate in two different ways. The first uses six of its O(Ph) atoms to µ-bridge between neighbouring metal ions, the two remaining O(Ph) atoms, positioned next to each other, being monodentate and chelating a single Ln ion. The second TBC [8] ligand contains five monodentate O(Ph) atoms, all positioned next to each other, and three µ-bridging O(Ph) atoms. The Cr III ion is six coordinate and in a distorted {CrO6} octahedral geometry, the sixth site being occupied by a MeOH molecule. The Ln III ions are of two types: five are eight coordinate and in square antiprismatic {LnO8} geometries, and one is seven coordinate and in pentagonal bipyramidal {LnO7} geometry, their coordination completed through the presence of dmf, MeOH and water molecules. Magnetic measurements revealed the Tb III analogue (29b) to be a SMM. A fit of the ac susceptibility data to the Arrhenius law (τ = τ0exp[Ueff/(kBT)]) revealed an effective energy barrier to magnetisation reversal of Ueff/kB = 18.13 K with a pre-exponential factor of τ0 = 7.5 × 10 -8 s.