Metallocyclic Cu^II–Ln^III Single-Molecule Magnets from the Self-Assembly of 1,4-Diformylnaphthalene-2,3-diol

We report the synthesis and characterization of seven new tetranuclear 3d–4f complexes derived from the 3:3:1 reaction of 1,4-diformylnaphthalene-2,3-diol (H2L) with copper­(II) nitrate and a lanthanide salt, Ln = Tb [L3Cu3TbCl2(NO3)2(H2O)2] (C1), Ho [L3Cu3HoCl3(H2O)3(MeOH)]­(H2O) (C2), Er [L3Cu3ErCl3(H2O)3.5(MeOH)0.5]­(H2O) (C3), Gd [L3Cu3Gd­(NO3)2(H2O)2(MeOH)]­(NO3) (C4), Dy [L3Cu3Dy­(NO3)2(H2O)2(MeOH)]­(NO3) (C5), Yb [L3Cu3Yb­(NO3)2(H2O)2(MeOH)]­(NO3) (C6), and La [L3Cu3La­(NO3)2(H2O)2(MeOH)]­(NO3) (C7). Structural elucidation showed that the self-assembly using the acyclic ligand system was successful for all seven complexes, which exhibit the same near-planar Cu3LnO12 core. Five complexes (C1, C2, and C4–C6) were magnetically characterized at 300 K and 1.8 K. Complexes C1, C4, and C5 were observed to have ferromagnetic ground states and showed appreciable frequency dependence in their AC magnetic measurements, which yielded effective barriers between 7.82(4) and 13.2(3) K, confirming the presence of single-molecule magnet properties.