Theoretical study of the exchange coupling substituting Mo(V) with W(V) in four cyano-bridged M'9M6 (M' = Mn(II) or Ni(II); M = Mo(V) or W(V)) systems.

Magnetic properties of four high-spin molecules [M'{M'(MeOH)3}8(mu-CN)30{M(CN)3}6] (M' = Mn(II) and M = Mo(V) for A; M' = Mn(II) and M = W(V) for B; M' = Ni(II) and M = Mov for C; M' = Ni" and M = W(V) for D) have been investigated using hybrid density functional theory (DFT) B3LYP with LANL2DZ basis set. Our calculations suggest that models [M'(mu-CN)6{M(CN)7}6](16-) (M' = Mn(II) and M = Mo(V) for A6; M' = Mn" and M = W(V) for B6; M' = Ni(II) and M = Mo(V) for C6; M' = Ni(II) and M = W(V) for D6) and [M'(MeOH)3(mu-CN)3{M(CN)7}3](7-) (M' = Mn(II) and M = Mo(V) for A3; M' = Mn(II) and M = W(V) for B3; M' = Ni(II) and M = Mo(V) for C3; M' = Ni(II) and M = W(V) for D3) are good candidates to model the complete molecular structures of A, B, C and D. For all complexes and models, the antiferromagnetic or ferromagnetic exchange interactions through equatorial cyanides are all stronger than those through apical cyanides. In Mn9M6 (A and B) systems, substituting Mo with W always enhances the antiferromagnetic interactions for the apical and equatorial cyanides and the different Cbrid-Nbrid-Mn angles, but the behavior is more complicated for Ni9M6 (C and D). Moreover, the calculated delta(xy) values of a series of binuclear models according to Kahn-Briat model were used to confirm our conclusions.