Is ferromagnetism an intrinsic property of the Cu-II/Gd-III couple? 2. Structures and magnetic properties of novel trinuclear complexes with mu-phenolato-mu-oximato (Cu-Ln-Cu) cores (Ln = La, Ce, Gd)

The present paper is devoted to the study of original trinuclear (Cu-II, Ln (III), Cu-II) complexes (Ln = La, Ce, Gd) They derive from the polydentate ligands H2Li (i = 1, 3, 4) represented in Figure 1. The crystal and molecul ar structures of two complexes have been determined at room temperature. Th e (Cu, Gd, Cu) complex of H2L1 1Gd and the (Cu, Ce, Cu) complex of H2L3 3Ce crystallize in the triclinic space group P (1) over bar (no. 2) with the f ollowing cell parameters: a = 14.005(2) Angstrom, b = 14.7581(13) Angstrom, c = 11.3549(13) Angstrom, alpha = 96.273(9)degrees, beta = 97.648(11)degre es, gamma = 72.946(9)degrees, V = 2217.7(4) Angstrom (3), and Z = 2 for 1Gd and a = 11.226(2) Angstrom, b = 16.927(3) Angstrom, c = 11.010(2) Angstrom , alpha = 108.67(2)degrees, beta = 110.48(1)degrees, gamma = 92.35(2)degree s, V = 1828.7(5) Angstrom (3), and Z = 2 for 3Ce. Regarding possible suppor ts for magnetic interactions, it may be noted that, in both complexes, each of the main bridging pathways between the equatorial positions of a copper (II) ion and the related lanthanide ion is double and not symmetrical. It i nvolves a phenolate oxygen atom and an oximato nitrogen-oxygen pair of atom s, The resulting Cu(O,N-O)Gd networks are not planar, but 3Ce displays much larger deviations than does 1Gd. Determination of the thermal dependence o f chi (M) (molar susceptibility) and the field variations of M (magnetizati on) show that in 3Gd and 4Gd the Cu-Gd interactions are antiferromagnetic w hile more "usual" ferromagnetic interactions are observed for 1Gd. The poss ibility of a relationship between structural and magnetic parameters is con sidered.