title: On the structure and spin states of Fe(III)-EDDHA complexes.
abstract: DFT methods are suitable for predicting both the geometries and spin states of EDDHA-Fe(III) complexes. Thus, extensive DFT computational studies have shown that the racemic-Fe(III) EDDHA complex is more stable than the meso isomer, regardless of the spin state of the central iron atom. A comparison of the energy values obtained for the complexes under study has also shown that high-spin (S = 5/2) complexes are more stable than low-spin (S = 1/2) ones. These computational results matched the experimental results of the magnetic susceptibility values of both isomers. In both cases, their behavior has been fitted as being due to isolated high-spin Fe(III) in a distorted octahedral environment. The study of the correlation diagram also confirms the high-spin iron in complex 2b. The geometry optimization of these complexes performed with the standard 3-21G* basis set for hydrogen, carbon, oxygen, and nitrogen and the Hay-Wadt small-core effective core potential (ECP) including a double-xi valence basis set for iron, followed by single-point energy refinement with the 6-31G* basis set, is suitable for predicting both the geometries and the spin-states of EDDHA-Fe(III) complexes. The presence of a high-spin iron in Fe(III)-EDDHA complexes could be the key to understanding their lack of reactivity in electron-transfer processes, either chemically or electrochemically induced, and their resistance to photodegradation.
authors.affiliation: Departamento de Química Organica, Facultad de Química, Universidad Complutense, 28040 Madrid, Spain. margg@quim.ucm.es
authors.forename: Mar
authors.initials: M
authors.lastname: Gómez-Gallego
authors.forename: Israel
authors.initials: I
authors.lastname: Fernández
authors.forename: Daniel
authors.initials: D
authors.lastname: Pellico
authors.forename: Angel
authors.initials: A
authors.lastname: Gutiérrez
authors.forename: Miguel A
authors.initials: MA
authors.lastname: Sierra
authors.forename: Juan J
authors.initials: JJ
authors.lastname: Lucena