Di- or Trinuclear 3d-4f Schiff Base Complexes: The Role of Anions

We demonstrate through structural, spectroscopic, and magnetic studies that the main factors governing the nuclearity of M-Gd (M = Cu, Nil complexes derived from compartmental Schiff base ligands are the different affinities of the lanthanide ions for the potential ligands and anions present in the reaction medium. In the eight examples studied, there is competition between the tetradentate O(2)O(2) coordination site of the polydentate ligand and the anionic entities brought by the gadolinium. salts. The strong affinity of nitrato anions for lanthanides yields dinuclear complexes and prevents formation of trinuclear entities, whereas the use of poorly coordinating anions such as triflates may yield either dinuclear or trinuclear complexes, depending on the 3d/4f ratio. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)