Abstract
The syntheses, structures and magnetic properties are reported of a new family of [Ln4Mn8O8(O2CPh)16(dmhmp)4] (Ln = Gd (1), Tb (2), Dy (3), Ho (4)) complexes obtained from the use in Mn–Ln chemistry of 2-(pyridine-2-yl)propan-2-ol (dmhmpH), a bulkier derivative of 2-(hydroxymethyl)pyridine (hmpH) containing a CMe2OH arm instead of CH2OH. Complexes 1–4 were obtained from the reaction of Mn(O2CPh)2, Ln(NO3)3, dmhmpH and NEt3 in a 2:1:2:4 molar ratio in MeCN/MeOH (24:2 mL), and the corresponding reaction with Y(NO3)3 gave [Y4Mn8O8(O2CPh)16(dmhmp)4] (5). The crystal structures of representative complexes 1 and 5 were solved and they are isostructural, with centrosymmetric structures comprising five metal-containing layers in an ABCBA arrangement, with A = Gd(Y), B = Mn2Gd(Y), and C = Mn4. Variable-temperature, solid-state dc and ac magnetic susceptibility studies on 1–5 revealed dominant antiferromagnetic interactions between the Mn8 unit and the LnIII ions. The data for 5 ostensibly indicated a well-isolated singly-degenerate ground state, but further studies suggested instead that the ground state is an S = 5 state that is near-degenerate with one or more states with S ≤ 4. Frequency-dependent ac in-phase χ′MT and out-of-phase χ″M signals indicate 3 (Dy) to possibly be an SMM, and this was confirmed by observation of hysteresis loops below 1.6 K in magnetization versus dc field scans below 2 K.
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