The Synthesis, Structures and Characterisation of New Mixed‐Ligand Manganese and Iron Complexes with Tripodal, Tetradentate Ligands

The preparation of new manganese and iron complexes with the general formula [M(tripod)(anion)] is described, where M = Fe III or Mn III , “tripod” is a dianionic tetradentate tripodal ligand and the anion is a chelating β‐diketonate, 8‐oxyquinoline or acetate. The synthesis of this type of complexes was found to be straightforward, which allows for the preparation of a large variety of such coordination compounds. The complexes are characterised by X‐ray crystallography, infrared spectroscopy, UV/Vis spectroscopy, cyclic voltammetry and elemental analysis. A correlation between the ligand sets and the electron density at the metal centre in the complexes is proposed, based on the UV/Vis data and the CV measurements. The tripodal ligands are significant π‐donor ligands, and electron‐withdrawing or electron‐donating substituents on the phenolate arms were found to have a large influence on both the position of the d–d transitions in the UV/Vis spectra and the peak potentials in the CV measurements. The “secondary” β‐diketonate or acetate ligand does not have such a large effect on the electron density of the metal centre.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)