Density functional study of magnetic exchange of dinuclear manganese complexes with the heteropolymolyanion: [MnII2(Xn+Mo9O33)2]2(n-10)-(X = PV, AsV, SeVI)

The magnetic exchange interactions between the dimanganese(II)-substituted complexes and the heteropolymolyanion, [Mn-II (2)(Xn+Mo9O33)(2)](2(n-10)-) (X = P-V(I), As-V(II) and Se-VI(III)), are investigated by using density functional theory combined with broken-symmetry approach (DFT-BS) method. The calculated magnetic exchange coupling constant (J) of complex II is in reasonable agreement with the responding experimental value and the negative J values indicate that antiferromagnetic exchange interactions exist in these complexes. Furthermore, the influence of the central heteroatom on the exchange coupling within the dimanganese core unit is studied from standpoints of geometry, spin density and frontier orbitals. It demonstrates that the change of the heteroatom X via PV - AsV - SeVI elongates the distances of Mn-1 center dot center dot center dot Mn-2 and shortens the distances of O-b center dot center dot center dot O-b, and reduces the effectiveness of the super-exchange pathways, consequently, decreasing the magnitude of the antiferromagnetic coupling constant, J, of these species.