Novel octadecanuclear copper( II )–lanthanoid( III ) clusters. Synthesis and structures of [Cu 12 Ln 6 (µ 3 -OH) 24 (O 2 CCH 2 CH 2 NC 5 H 5 ) 12 (H 2 O) 16 (µ 12 -ClO 4 )][ClO 4 ] 17 ·16H 2 O (Ln III = Gd III or Sm III )

Two octadecanuclear clusters [Cu12Ln6(µ3-OH)24(O2CCH2CH2NC5H5)12(H2O)16(µ12-ClO4)][ClO4]17·16H2O (LnIII= GdIII or SmIII) have been synthesized and characterized by X-ray structural analysis. The clusters are isostructural, crystallizing in the triclinic space group P with Z= 1. In each structure six LnIII are positioned at the vertices of an octahedron with twelve CuII at the midpoints of the edges of the octahedron. The 24 OH– groups act as µ3 bridges each ligating one LnIII and two CuII. The octahedron encapsulates an unusual µ12-ClO4– anion of which each oxygen atom co-ordinates to three CuII at the axial positions. Ten of the C5H5N+CH2CH2CO2– ligands act in the µ-carboxylato-O,O′ mode, while the other two act in the carboxylato-O,O′ mode each chelating a LnIII, resulting in different co-ordination environments for the CuII and LnIII.