Magnetic anisotropy in cyanide complexes of first row transition metal ions

Abstract

The relationship between structure and magnetic anisotropy in monoand oligonuclear paramagnetic complexes, based on low-spin [Fe(CN)6] 3- and hexacoordinate NiII complexes with bridging CN- groups, are analyzed with special emphasis on the contributions of spin-orbit coupling and Jahn-Teller distortions as well as strain-induced distortions at the [Fe(CN)6]3- subunit. The basic theoretical principles are described, which allow to treat the lowest multiplets of FeIII and Ni II, due to the t2g5 and t2g6e2g electronic configurations, respectively, and their anisotropic exchange coupling. Examples are then presented, to show how small angular distortions of [Fe(CN)6]3- lead to dramatic changes of the magnetic anisotropy of the corresponding oligonuclear complexes. The nature of the lowest spin multiplet and the spin-anisotropy gap are analyzed with a combination of density functional theory and ligand field theory (LFDFT). A general ab-initio approach is also proposed, which allows to calculate the magnetic anisotropy of oligonuclear complexes with transition metals in orbitally degenerate or nearly-degenerate electronic ground states. © Springer Science+Business Media B.V. 2010.