A Density Functional Theory Study of the Magnetic Exchange Coupling in Dinuclear Manganese(II) Inverse Crown Structures

The magnetic exchange coupling constants between two Mn(II) centers fora set of five inverse crown structures have been investigated by means of a methodology based oil broken-symmetry unrestricted density functional theory. These novel and highly unstable compounds present superexchange interactions between two Mn centers, each one with S = 5/2 through anionic guests Such as oxygen, benzene, or hydrides or through the cationic ring formed by amide ligands, and alkali metals (Na, Li). Magnetic exchange Couplings calculated at B3LYP/6-31G(d,p) level yield strong antiferromagnetic couplings for compounds linked via all oxygen atom or hydride and very small antiferromagnetic Couplings for those linked via a benzene molecule, deprotonated in either 1,4- or 1,3- positions. Analysis of the magnetic orbitals and spin polarization maps provide ail Understanding of the exchange mechanism between the Mn centers. The dependence of J with respect to 10 different density functional theory potentials employed and the basis set has been analyzed.