Density functional modeling of double exchange interactions in transition metal complexes.: Calculation of the ground and excited state properties of [Fe2(OH)3(tmtacn)2]2+

Density functional theory has been successfully applied to characterize the electronic structure and the magnetic properties of the mixed valence dinuclear complex [Fe-2(OH)(3)(tmtacn)(2)](2+) modeled by replacing the tmtacn ligand with three ammonia molecules. Spectroscopic and magnetic properties have been computed in nice agreement with the experimental values. Minimum energy path calculations allowed us to compute the frequencies associated with the normal coordinate Q(-) responsible for the delocalization of the extra electron, and we resent here a procedure for the full characterization of mixed-valence transition metal dimers.