title: Magnetic exchange coupling in bis-nitroxides: a theoretical analysis of the solvent effects.
abstract: Magnetic properties of nitroxide radicals can be greatly affected by solvent effects. In this study, the change of the magnetic exchange interaction J, coupling the two unpaired electrons of a model solvated antiferromagnetic bis-iminyl-nitroxide molecule (2IN), is rationalized thanks to different geometric and electronic criteria provided by density functional theory calculations. It is shown that for a given geometry, simple tools can be used to analyze with good accuracy the dependence of J with the solvent polarity. Estimates of two important magnetic parameters are given: the magnetic orbitals exchange and the in-site energy gap between ionic and neutral configurations. 2IN can be engaged in different hydrogen-bonds with first shell water molecules, modifying both the 2IN geometry and the electrostatic potential felt by the molecule. In all, the additivity of electrostatic and hydrogen-bond solvent effects is found to be responsible for J variations as large as 50%.
authors.affiliation: Aix-Marseille Université, Institut de Chimie Radicalaire, Marseille, France.
authors.forename: Esther
authors.initials: E
authors.lastname: Coulaud
authors.forename: Denis
authors.initials: D
authors.lastname: Hagebaum-Reignier
authors.forename: Didier
authors.initials: D
authors.lastname: Siri
authors.forename: Paul
authors.initials: P
authors.lastname: Tordo
authors.forename: Nicolas
authors.initials: N
authors.lastname: Ferré
mesh_terms: D008280:Magnetics; D009589:Nitrogen Oxides / Q000737:chemistry*; D011789:Quantum Theory; D012997:Solvents / Q000737:chemistry
chemical_list: D009589:Nitrogen Oxides; D012997:Solvents