Four Mixed 3d-4f 12-Metallacrown-4 Complexes: Syntheses, Structures and Magnetic Properties

The incorporation of LnIII ions into the 12-metallacrown-4 topology affords the formation of four mixed 3d-4f pentanuclear complexes of compositions [NH(C2H5)3]{[Ln(OAc)4] [12-MCMnIII(N)shi-4]}·xH2O (Ln = Sm (1), Gd (2), Tb (3), Dy (4); x = 0.5 for 1 and 3, x = 0.25 for 2, x = 0 for 4; H3shi = salicylhydroxamic acid). Compounds 1–4 were obtained from the reactions of H3shi with Mn(CH3COO)2·4H2O and Ln(NO3)3·6H2O, in the presence of N(C2H5)3. They all contain a crown-like [Mn4Ln(μ-NO)4]11+ core with four MnIII atoms being at the rim of the crown and an LnIII ion occupying the dome of the crown. The peripheral ligation about the core is provided by four η1:η1:µ acetate groups. The identity of the LnIII ions slightly affects the 12-metallacrown-4 frameworks, as demonstrated by the gradual decrease of the distances between the LnIII ions and the centres of the Mn4 planes (1.85 Å for 1, 1.81 Å for 2, 1.80 Å for 3, and 1.77 Å for 4). Variable-temperature dc magnetic susceptibility studies were carried out on polycrystalline samples of 1–4. Antiferromagnetic interactions are determined for complexes 1–4.