LANTHANIDE(III)-COPPER(II) MOLECULAR-COMPOUNDS WITH A LADDER-LIKE MOTIF - STRUCTURE AND MAGNETIC-PROPERTIES

The reaction of Ln(III) ions with the precursor [Cu(opba)](2-) in DMF has afforded a series of structurally isomorphous compounds of formula Ln(2)[Cu(opba)](3) . xDMF . yH(2)O (x approximate to 10, y approximat e to 4); Ln stands for a lanthanide atom, from Tb to Lu, or for Y, opb a stands for ortho-phenylenebis(oxamato), and DMF stands for dimethylf ormamide. The crystal structure has been solved for Ln = Tm. The space group is P2(1)2(1)2(1), with a = 9.864(2) Angstrom, b = 20.855(2) Ang strom, c = 39.101(9) Angstrom, Z = 4 The structure consists of ladder- type motifs, parallel to each other, with infinite Tm[Cu(opba)] sidepi eces and [Cu(opba)] rungs joining two Tm atoms. The temperature depend ences of the magnetic susceptibility for all compounds have been inves tigated, and have revealed a striking difference between the compounds with Ln = Tb and Dy and those with Ln = Ho, Er, Tm, and Yb. For the f ormer compounds, significant Ln(III)-Cu(II) magnetic interactions have been detected, which leads to the divergence of the product chi(M)T o f the molar magnetic susceptibility with temperature. At this stage, i t has not been possible to specify whether the compounds are one-dimen sional ferri- or ferromagnets. In contrast, for the Ln = Ho, Er, Tm an d Yb compounds, the Ln(III)-Cu(II) interactions, if any, are hidden by the crystal field effects.