Construction of a robust pillared-layer framework based on the rare paddlewheel subunit [Mn II2(μ-O2CR)4L2]: synthesis, crystal structure and magnetic properties

Abstract

With numerous examples of heavier congeners as well as neighbors, only four paddlewheel compounds, including one coordination architecture, of manganese with the [Mn^II₂(μ-O₂CR)₄L₂] core were reported in the literature. We report here a robust pillared-layer framework with an α-polonium topology comprising such a core as a subunit, {[Mn₂(O₂CC₆H₄Si(CH₃)₂C₆H₄CO₂)₂(4,4′-bpy)]}_n (1), where 4,4′-bpy = 4,4′-bipyridine, with an Mn⋯Mn distance of 3.005(2) Å, which does not vary with temperature. For the first time, the variable temperature magnetic data (2–300 K) and crystal structures at two different temperatures (100 K and 296 K) are combined for the same example to support the fact that there is no metal–metal bond in such compounds like 1. Based on the magnetic measurements, an antiferromagnetic interaction (2J = −12.4 cm⁻¹ with g = 2.014 (H = −2JS₁S₂)) between two S₁ = S₂ = 5/2 spin centers exists in 1.