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). 4H(2)O (1), [Cu(II)(12-((II)N(hbha))-4)] .(NO3)(2) . 8H(2)O (2) and [Cu(II)(12-MCCu(II)N(mha)-4)].(OH)(2) 12H(2)O (3) (H(2)ahpha = 3-amino-3-hydroximino propanoic hydroximic acid, H(2)hbha = 3-hydroximino butanoic hydroximic acid and H(2)mha = 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 = - 2J(1) Sigma(i=1)(4) S-i . S-5 - 2J(2) Sigma(i not equal j=1)(4) S-t.S-j to the experimental magnetic susceptibilities give g = 2.066(3), J(1)= - 119.9(7), J(2)= -79.0(4), zJ' = - 0.69(7) cm(-1) for 1 and g = 2.089(3), J(1) = - 163(2), J(2) = - 85.1(6), zJ' = - 0.61(7) cm(-1) for 2. (C) 2000 Elsevier Science S.A. All rights reserved.