Cyanide-bridged W^VMn^III bimetallic chains composed of a blocked W hexacyanide precursor: Geometry-related magnetic couplings and magnetostructural correlation

Five one-dimensional bimetallic W^VMn^III 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-N_ax (ax = axial) bond length increases when moving from 1 to 2, with the Mn-N_ax-C_ax 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-N _ax bond lengths are similar across all the samples, the increase in the Mn-N_ax-C_ax angles accounts for the enhanced magnetic strength. Notably, a correlation between structure and magnetic exchange coupling is established for the first time in W^VMn^III bimetallic systems based on the [W(CN)₆(bpy)]^- precursor.