Crystal and molecular structure and magnetic properties of a trinuclear complex containing exchange-coupled GdCu2 species

gadolinium(II1) and europium(II1) nitrate to yield a compound of formula (CUSAL~~)~M(H,O)(NO~)~(.M~ =E ~euNroOp,ium( III), gadolinium(II1)). The crystal structure of the gadolinium complex was determined at room temperature: the compound crystallizes in the triclinic space group Pi, with a = 15.694 (2) A; b = 14.887 (1) A, c = 10.574 (2) A, a = 95.44 (O)O, p = 103.18 ( 5 ) O , y = 106.95 (O)’, and Z = 2. Least-squares refinement of the structure led to a conventional R factor of 0.041. The europium(I11) ion derivative was found to be isomorphous. The gadolinium(II1) ion is nine-coordinated by the oxygen atoms of two CuSALtn moieties, two bidentate nitrate ions, and one water molecule. The coordination geometry can be described as a tricapped trigonal prism. The effective magnetic moment of the compound was found to increase on decreasing the temperature. The experimental points were fit to a spin-Hamiltonian model for symmetric triples of spins, to yield a weak ferromagnetic gadolinium(II1)-copper(1I) interaction and a weak antiferromagnetic copper(I1)-copper(I1) interaction. The coupling between the two copper ions was confirmed by the triplet EPR spectra of the europium(II1) derivative.