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

Abstract

Five one-dimensional bimetallic W^VMn^III complexes <b>1</b>–<b>5</b>, 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 <b>1</b> and <b>2</b>, and a distorted square antiprism (SAPR) for <b>3</b>–<b>5</b>. Magnetic analyses demonstrate that compounds <b>1</b>, <b>4</b>, and <b>5</b> exhibit antiferromagnetic interactions between magnetic centers, which are different from the ferromagnetic couplings in <b>2</b> and <b>3</b>. For the distorted DD geometry, the Mn–N_ax (ax = axial) bond length increases when moving from <b>1</b> to <b>2</b>, 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 <b>2</b>. In comparison, for <b>3</b>–<b>5</b> 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