CRYSTAL AND MOLECULAR-STRUCTURE OF AND MAGNETIC COUPLING IN 2 COMPLEXES CONTAINING GADOLINIUM(III) AND COPPER(II) IONS

The tetradentate copper(I1) Schiff base complexes CuHAPen and CuSALen react with Gd(C10)4)3 to yield crystalline materials of formula [(CUHAP~~)~G~(H~O)~](C~O,)(I~) .anZdC [U(HCAUPS~A~L ~~)~G~(H,O)~](C~O~)~.~CUSAL~~. 0.5CzH5N02 (II), respectively. Their crystal structures were determined through X-ray diffraction at room temperature: I crystallizes in the monoclinic system, space group C2/c with lattice constants a = 16.092 (4) A, 6 = 31.262 (6) A, c = 15.249 (4) A, @ = 95.44 ( 5 ) ’ , with Z = 4; and I1 crystallizes in the monoclinic system, space group P2,/a with lattice constants a = 18.333 ( 5 ) A, b = 33.233 (7) A, c = 11.864 (3) A, @ = 95.94 ( 5 ) ’ , with Z = 4. Least-squares refinement of the structure led to a conventional R factor of 0.059 (I) and 0.061 (11). In both structures a tripositive ion, three perchlorate, and two copper Schiff base molecules are present. In the tripositive ion a central gadolinium(II1) is bound in a distorted pentagonal-bipyramidal fashion to three water molecules and to four oxygen atoms of two copper(I1) Schiff base complexes. The temperature dependence of the magnetic susceptibility of both I and I1 was investigated in the range 1.2-300 K. The effective magnetic moments of both compounds have been found to increase steadily on decreasing temperature. These data have been interpreted with use of a Heisenberg spin Hamiltonian in the following form: 3f s J(S1.S2+ S2.S3)+ J’S1.S3w, here 1 and 3 refer to copper(I1) ions and 2 refers to gadolinium. The least-squares fit of the experimental susceptibilities yielded g = 1.992 (4), J = -5.32 (5) cm-’, J’= 4.2 (3) cm-’ for I and g = 1.97 (l), J = -7.38 (7) cm-’, J’= 12.23 (3) cm-’ for 11. The observed Gd-Cu coupling is ferromagnetic and fairly substantial, a result which opens new perspectives in the field of magnetic interactions between rare-earth and transition-metal ions.