Unprecedented hexagonal bipyramidal single-ion magnets based on metallacrowns

Two novel Ln( iii ) (Ln = Ce or Nd) complexes based on [15-MC-6] (MC = metallacrown) and phosphine oxide are reported. Both of them feature a hexagonal bipyramidal LnO 8 geometry ( D 6h ) and behave as single-ion magnets. Two Ln( iii ) (Ln = Ce or Nd) complexes based on [15-MC-6] (MC = metallacrown) and phosphine oxide are reported for the first time with the Ln( iii ) ion featuring nearly perfect hexagonal bipyramidal LnO 8 geometry, with pseudo- D 6h symmetry. Magnetic measurements reveal that both behave as single-ion magnets (SIMs), where the slow relaxation is dominated by the Raman mechanism.