Two new diphenoxo-bridged discrete dinuclear CuIIGdIII compounds with cyclic diimino moieties:: Syntheses, structures, and magnetic properties

Two Schiff base compartmental ligands, H2L1 and H2L2, derived from the condensation of 3-ethoxysalicylaldehyde with 1,2-diaminocyclohexane and orthophenylenediamine, respectively, have been utilized to isolate two diphenoxo-bridged discrete dinuclear (CuGdIII)-Gd-II complexes, [Cu-II(H2O)-(LGdIII)-Gd-1(NO3)(3)] (3) and [(CuLGdIII)-L-II-Gd-2(NO3)(3)] (4). This is the first report on the 3d-4f compounds derived from compartmental Schiff base ligands with cyclic diamines. The compounds 3 and 4 crystallize in the triclinic P (1) over bar and orthorhombic Pna2(1) space groups, respectively, with the following unit cell parameters - 3: a = 8.8713(2) angstrom, b = 12.8399(3) angstrom, c = 14.0067(3) angstrom, a = 80,6649(5)degrees, beta = 77.4059(5)degrees, gamma = 76.8879(5)degrees, and Z = 2; 4: a = 9.2210(1) angstrom, b = 16.5407(2) angstrom, c = 19.9248(4) angstrom, and Z = 4. Structural analysis reveals that both are discrete dinuclear complexes. In 3, one water molecule is coordinated to the copper(II) ion to result in a square-pyramidal coordination geometry, while the geometry of the coppe(II) center in 4 is square planar. In both complexes, the gadolinium(III) center has an O-10 coordination environment. In contrast to expectation, although the N2O2 cavity affords a better planar environment for the copper(II) center in 4, the bridging moiety in complex 3 is more planar than that in 4 or in most of the previously reported examples (the dihedral angle between two CuO2Gd planes: 2.1 degrees for 3 and 7.1 degrees for 4). Variable-temperature and variable-field magnetic measurements reveal that the metal centers in both the complexes are terromagnetically coupled (J values: 6.3 cm(-1) for 3 and 5.4 cm(-1) for 4; H = -2JS(Cu)(.)S(Gd)), Interestingly, complex 3 exhibits strongest ferromagnetic interaction among the related compounds. (c) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005.