A Family of [Mn₆] Complexes Featuring Tripodal Ligands

The synthesis and magnetic properties of four new Mn complexes containing tripodal alcohol ligands are reported: [Mn6(OAc)6(H2tea)2(tmp)2]·2MeCN (1·2MeCN), [Mn6(acac)4(OAc)2(Htmp)2(H2N-ep)2] (2), [Mn6(OAc)8(tmp)2(py)4]·2py (3·2py), and [Mn6(OAc)8(thme)2(py)4]·2py (4·2py) [H3tea, triethanolamine; H3tmp, 1,1,1-tris(hydroxymethyl)propane; H2N−H2ep, 2-amino-2-ethyl-1,3-propanediol; H3thme, 1,1,1-tris(hydroxymethyl)ethane]. All complexes are mixed-valent with a [MnIII2MnII4] oxidation assignment and are constructed from four edge-sharing triangles but differ slightly in that complexes 1 and 2 display a [MnIII2MnII4(μ2-OR)6(μ3-OR)4]4+ core, while complexes 3 and 4 feature [MnIII2MnII4(μ2-OR)2(μ3-OR)4]8+ and [MnIII2MnII4(μ2-OR)4(μ3-OR)4]6+ cores, respectively. dc and ac magnetic susceptibility studies in the 2−300 K range for complexes 1−4 reveal the presence of dominant antiferromagnetic exchange interactions, leading to ground states of S = 0 for 1 and 2, while complexes 3 and 4 display S = 4 ground states with D = −0.44 and −0.58 cm-1, respectively. Single-molecule magnetism behavior was confirmed for 3 and 4 by the presence of sweep-rate and temperature-dependent hysteresis loops in single-crystal M vs H studies at temperatures down to 40 mK. Theoretical density functional calculations were used to evaluate the individual pairwise exchange interactions present, confirming the diamagnetic ground states for 1 and 2 and the S = 4 ground states for 3 and 4.