Theoretical study on magnetic interaction in pyrazole-bridged dinuclear metal complex: Possibility of intramolecular ferromagnetic interaction by orbital counter-complementarity

Abstract

A possibility of the intramolecular ferromagnetic (FM) interaction in pyrazole-bridged dinuclear Mn(II), Fe(II), Co(II), and Ni(II) complexes is examined by density functional theory (DFT) calculations. When azide is used for additional bridging ligand, the complexes indicate the strong antiferromagnetic (AFM) interaction, while the AFM interaction becomes very weak when acetate ligand is used. In the acetate-bridged complexes, an energy split of the frontier orbitals suggests the orbital counter-complementarity effect between the dxy orbital pair, which contributes to the FM interaction; however, a significant overlap of other d-orbital pairs also suggests an existence of the AFM interaction. From those results, the orbital counter-complementarity effect is considered to be canceled out by the overlap of other d-orbital pairs.