Density functional study of magnetic exchange of dinuclear manganese complexes with the heteropoly-molyanion:[Mn^(II)_2(X^(n+)Mo_9O_(33))_2]^(2(n-10)-) (X=P^V, As^V, Se^(VI))

The magnetic exchange interactions between the dimanganese(II)-substituted complexes and the het-eropolymolyanion, [MnII2(Xn+Mo9O33)2]2(n-10)-(X = PV(I), AsV(II) and SeVI(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 cou-pling within the dimanganese core unit is studied from standpoints of geometry, spin density and fron-tier orbitals. It demonstrates that the change of the heteroatom X via PV-AsV-SeVI elongates the dis-tances of Mn1···Mn2 and shortens the distances of Ob···Ob, and reduces the effectiveness of the super-exchange pathways, consequently, decreasing the magnitude of the antiferromagnetic coupling constant, J, of these species.