Two chain complexes of [(CH3)2NH2] [M(N3)2(HCOO)] (M=Fe and Co) studied by first-principle electronic-structure calculation

The electronic structures of two ferromagnetic polynuclear complexes, where the anionic [M(N3)2(HCOO)−]n chains with a 3-fold bridge of two end-on (EO) azido and one sys-syn formato ligands are isolated by the cations of [(CH3)2NH2]+, have been studied using the full-potential linearized augmented plane wave method based on the density functional theory (DFT). The result shows that spin populations in these two complexes are mainly distributed on the octahedron by four nitrogen atoms and two oxygen atoms of two formats at apical sites that surround the metal ions (M=Fe and Co). There are large and positive spin populations on metal ions, small and positive spin populations on the oxygen and nitrogen atoms of the anionic [M(N3)2(HCOO)−]n chains. Ferromagnetic coupling through the two EO-azido bridges in these two complexes has been mainly attributed to the spin delocalization, also with weak spin polarization effect.