A family of [Mn-6] complexes featuring tripodal ligands

The synthesis and magnetic properties of four new Mn complexes containing tripodal alcohol ligands are reported: [Mn-6(OAc)(6)(H(2)tea)(2)(tmp)(2)]center dot 2MeCN (1 center dot 2MeCN), [Mn-6(acac)(4)(OAc)(2)(Htmp)(2)(H2N-ep)(2)] (2), [Mn-6(OAc)(8)(tmp)(2)(py)(4)]center dot 2py (3, 2py), and [Mn-6(OAc)(8)(thme)(2)(py)(4)]center dot 2py (4, 2py) [H(3)tea, triethanolamine; H(3)tmp, 1,1,1-tris(hydroxymethyl) propane; H2N-H(2)ep, 2-amino-2-ethyl-1,3-propanediol; H(3)thme, 1,1,1-tris(hydroxymethyl) ethane]. All complexes are mixed-valent with a [(Mn2Mn4II)-Mn-III] oxidation assignment and are constructed from four edge-sharing triangles but differ slightly in that complexes 1 and 2 display a [(Mn2Mn4II)-Mn-III(mu(2)-OR)(6)(mu(3)-OR)(4)](4)(+) core, while complexes 3 and 4 feature [Mn(2)(III)Mn(II)4(A(2)-OR)(2)(A(3)-OR)(4)](8+) and [(Mn2Mn4II)-Mn-III(A(2)-OR)(4)(A(3)-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.