DFT description of mixed valence magnetic systems. Mn(III)-Mn(IV) and Fe(II)-Fe(III) complexes

Density functional theory has been successfully applied to characterize the electronic sturcture and the magnetic properties of the mixed-valence dinu clear complex [Fe-2(OH)(3)(tmtacn)(2)](2+[1]'[2]), modeled by replacing the tmtacn ligand with 3 ammonia molecules, and the complex [Mn-2(O)(2)(NH3)(8 )](3+[3]), where the ammonia modeled two Tren ligands. Spectroscopic and ma gnetic properties have been computed in nice agreement with the experimenta l values. Minimum energy path calculations allowed us to compute the freque ncies v(-) associated to the normal coordinate Q(-) responsible of the delo calization of the extra electron and we present here a procedure for the fu ll characterization of mixed-valence transition metal dimers.