Preparation, crystal structures and magnetic properties of 12-metallacrown-4 complexes with the donors on the organic periphery of molecule

As the precursors of molecular magnets, three metallacrown analogous complexes, [Cu(II)(12-MCCu(II)N(ahpha)-4)]·(NO3)2·4H2O (1), [Cu(II)(12-(II)N(hbha)-4)]·(NO3)2·8H2O (2) and [Cu(II)(12-MCCu(II)N(mha)-4)]·(OH)2·12H2O (3) (H2ahpha=3-amino-3-hydroximino propanoic hydroximic acid, H2hbha=3-hydroximino butanoic hydroximic acid and H2mha=malonic hydroximic acid) have been prepared and 1 and 2 are characterized structurally. The number of donors on the organic periphery of the molecular sheet is modified with additional hydroxy and R group of ligands for modulating the intermolecular architecture of metallacrown molecules and enhancing intermolecular magnetic interaction. Solid-state magnetic susceptibility studies 5–300 K of 1 and 2 show a strongly antiferromagnetic intramolecular exchange between the five Cu(II) centers and weakly antiferromagnetic intermolecular interaction. The fitting of H=−2J1 ∑4i=1 Si·S5−2J2 ∑4i≠j=1 Si·Sj to the experimental magnetic susceptibilities give g=2.066(3), J1=−119.9(7), J2=−79.0(4), zJ′=−0.69(7) cm−1 for 1 and g=2.089(3), J1=−163(2), J2=−85.1(6), zJ′=−0.61(7) cm−1 for 2.