Magnetic field and dilution effects on the slow relaxation of {Er3} triangle-based arsenotungstate single-molecule magnets

A triangular {Er-3} cluster containing polyoxometalate (POM), [Er-3(mu(3)-OH)(H2O)(8)(As W9O33)(As W10O35(dl-mal))](2)(22-)(1) (mal = malate), has been obtained via one-pot reactions. Structural analyses demonstrate that three Er(3+)ions bridged one mu(3)-OH to generate a rare mu(3)-OH-capped triangular {Er-3} cluster, which connects two different vacant polyanions to form an unsymmetrical sandwich-type subunit, and adjacent sandwiched subunits are linked through mal ligands to give the targeted dimer. When the Er(3+)ions are substituted in whole or in part with Y(3+)ions, the diamagnetic yttrium analogue [Y-3(mu(3)-OH)(H2O)(8)(AsW9O33)(AsW10O35(dl-mal))](2)(22-)(2) and diluted sample [Er0.15Y2.85(mu(3)-OH)(H2O)(8)(AsW9O33)(AsW10O35(dl-mal))](2)(22-)(Er@2) have also been synthesized. Magnetic studies reveal that 1 exhibits field-induced two-step magnetic relaxation processes; the slow relaxation process may arise from intramolecular magnetic interactions, whereas the fast one is likely to originate from the intermolecular dipole-dipole interactions supported by the magnetic results of Er@2. From ab initio calculations, it is found that although the magnetic an isotropies of 1 mainly originate from individual Er3+ fragments, the Er3+-Er3+ interactions have a considerable influence on their slow magnetic relaxation processes.