title: Energetics of binuclear spin transition complexes.
abstract: The electronic structures of five binuclear iron(II) complexes, four of which display spin transitions between the low-spin (LS) and high-spin (HS) electronic states, are studied by density functional theory (DFT) calculations. Three electronic states, corresponding to [LS-LS], [LS-HS], and [HS-HS] electronic configurations, are characterized. The nature of the ground state agrees with the experimentally observed magnetic state of complexes stabilized at low temperatures. The results of the calculations agree with the conclusion of the phenomenological model, that the enthalpy of the [LS-HS] state must be lower than the average enthalpy of the [LS-LS] and [HS-HS] states, to create conditions for a two-step spin transition. The exchange parameters between Fe(II) ions in the [HS-HS] states are evaluated. It is shown that all complexes are weakly antiferromagnetic and the synergy between two spin transition centers is mainly of elastic origin.
authors.affiliation: Laboratoire de Chimie, UMR 5182 CNRS, Ecole Normale Supérieure de Lyon, 46 allée d'Italie, 69364 Lyon Cedex 07, France.
authors.forename: Samir
authors.initials: S
authors.lastname: Zein
authors.forename: Serguei A
authors.initials: SA
authors.lastname: Borshch