Cyanide-Bridged WVMnIII Bimetallic Chains Composed of a Blocked W Hexacyanide Precursor: Geometry-Related Magnetic Couplings and Magnetostructural Correlation

Five one-dimensional bimetallic WVMnIII complexes 1–5, consisting of [W­(CN)6(bpy)]− anions and [Mn­(Schiff base)]+ cations, were prepared. The central coordination geometry around each W atom is determined as a distorted dodecahedron (DD) for 1 and 2, and a distorted square antiprism (SAPR) for 3–5. Magnetic analyses demonstrate that compounds 1, 4, and 5 exhibit antiferromagnetic interactions between magnetic centers, which are different from the ferromagnetic couplings in 2 and 3. For the distorted DD geometry, the Mn–Nax (ax = axial) bond length increases when moving from 1 to 2, with the Mn–Nax–Cax angle remaining constant. The elongation of the bond length is responsible for the reduction in orbital overlap and consequent ferromagnetic coupling in 2. In comparison, for 3–5 with the distorted SAPR geometry, given that the Mn–Nax bond lengths are similar across all the samples, the increase in the Mn–Nax–Cax angles accounts for the enhanced magnetic strength. Notably, a correlation between structure and magnetic exchange coupling is established for the first time in WVMnIII bimetallic systems based on the [W­(CN)6(bpy)]− precursor.