title: DFT and the electromerism in complexes of iron with diatomic ligands.
abstract: A reliable procedure is proposed for assigning the electronic structures for large biologically-relevant systems, where the size of the model confines one to the use of density functional theory (DFT) methods, and where the risk of over-interpreting DFT-derived molecular orbitals and spin densities still exists. The proposed approach focuses on the use of the only DFT-derived parameter that is unanimously recognized to be reliable: the geometry. We examine DFT-derived O-O bond lengths in formally ferrous-dioxygen models, and compare them to bond lengths in free, non metal-bound, dioxygen, superoxide and peroxide moieties. Likewise, we compare the N-O bond lengths within ferrous-nitrosyl {FeNO}7 models, with the same parameter in free NO+, NO*, and HNO species. This allows a calibrated, straightforward way of assigning the electronic structure in systems where electromerism makes detailed single-reference molecular orbital analysis unreliable.
authors.affiliation: Department of Biological Sciences, University of Essex, Wivenhoe Park, Colchester CO4 3SQ, United Kingdom. rlsila@essex.ac.uk
authors.forename: Radu
authors.initials: R
authors.lastname: Silaghi-Dumitrescu
authors.forename: Ioan
authors.initials: I
authors.lastname: Silaghi-Dumitrescu
mesh_terms: D005290:Ferric Compounds / Q000737:chemistry*; D005296:Ferrous Compounds / Q000737:chemistry*; D006418:Heme / Q000737:chemistry; D008024:Ligands; D008956:Models, Chemical; D008958:Models, Molecular; D010100:Oxygen / Q000737:chemistry
chemical_list: D005290:Ferric Compounds; D005296:Ferrous Compounds; D008024:Ligands; D006418:Heme; D010100:Oxygen