A novel di-iron(III) structure based on an ageless ligand

摘要

Salen-type Schiff base ligands possess a N2O2 Coordination site able to chelate transition metal ions. Reaction of such a ligand with FeCl3 center dot 6H(2)O leads to the formation of a genuine dinuclear L3Fe2 complex in which the ligand plays a double role. The structural determination confirms that each iron ion is wrapped up by a chelating tetradentate ligand while the third one ensures a bridge in between the two Fe ions and completes to six the metal coordination sphere. Such a bridge implies a non planar coordination of the chelating ligands and induces helicity around each metal ion. Crystals are true racemates made of homochiral Lambda-Lambda and Delta-Delta pairs. The magnetic study confirms the absence of a spin exchange interaction through the saturated diamino chain and the presence of an axial single ion zero field splitting (ZFS) D equal to -0.7 cm(-1). The Mossbauer spectra show a unique asymmetric quadrupole-split doublet with isomer shift values, delta, of 0.342(2), 0.438(2) and 0.450(2) mm s(-1), and quadrupole splittings, Delta E-Q, of 0.826(4), 0.836(4) and 0.827(4) mm s(-1) at 293, 80 and 4.5 K, respectively. These values are in agreement with a high-spin iron(III) site in a N3O3 ligand environment.