Methylene spacer regulated variation in structures and magnetic properties in copper(II) compounds with O, N, O donor Schiff bases

Tetranuclear [Cu-4(L-1)(2)(HL1)(2)(H2O)](ClO4)(2)center dot 2H(2)O (1) and binuclear [Cu-2(L-2)(2)]center dot CH3OH (2) compounds are prepared and the molecular structures elucidated on the basis of X-ray crystallography [H2L1 = 2-1(2-hydroxy-ethylimino)-methyl]-6-methoxy-phenol, H2L2 = 2-[(3-hydroxy-propylimino)-methyl]-6-methoxy-phenol]. Compound 1 is made up of the cation [Cu-4(L-1)(2)(HL1)(2)(H2O)(2)](2+) and two ClO4- anions which are H-bonded to the cation. The four Cu(II) atoms are not crystallographically equivalent, among then two are in tetragonal [CuNO5] geometries and the rest two are in square pyramidal geometries. The asymmetric unit of compound 2 consists of one neutral [Cu-2(L-2)(2)] moiety and a methanol molecule. Each copper atom in compound 2 has a four-coordinate square-planar environment. Compound 1 can be described as an open cage with a [Cu-4(mu(3)-O-al)(2)(mu(2)-O-ph)(2)](4+) core (al = alkoxido and ph = phenoxido). Variable temperature solid state magnetic studies between 2-300 K were carried out and the data indicate predominant antiferromagnetic exchange interactions and a spin ground state S = 0. The data were fitted with an average J value model, using the spin Hamiltonian H = -J(av)(S-1 center dot S-2 + S-3 center dot S-4 + S-1 center dot S-3 + S-2 center dot S-4). The best fit was obtained with J(av) = -99.0 cm(-1). The magnetic properties of compound 2 have also been analyzed and the data show a large antiferromagnetic interaction, in agreement with the [Cu-2(mu(2)-O-al)(2)](2+) core. The best fit of the data was obtained with J = -891 cm(-1) (H = -J S-1 center dot S-2). (c) 2012 Elsevier Ltd. All rights reserved.