Proton NMR Investigations of Intermediate Spin Iron(III) Complexes with Macrocyclic N42– Chelate Ligands

Proton NMR spectra of five macrocyclic iron(III) intermediate-spin complexes are investigated. The signal assignment was accomplished for all five complexes. The temperature dependence of the NMR spectra reveals that for complexes of the type Fe1 an ideal Curie behaviour is observed indicating the absence of excited states. This is not the case for complexes of the type Fe2 and Fe3. A significant deviation from the Curie straight line is observed for Fe3-Cl indicating low-lying excited states. Single crystals suitable for X-ray structure analysis were obtained for the complexes Fe2-Cl and Fe3-I and the X-ray structure of those two complexes is presented.