Construction of a robust pillared-layer framework based on the rare paddlewheel subunit [Mn(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(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 MnMn 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.