Pentanuclear heterobimetallic 3d-4f complexes of Ln2M3-type -: structure and magnetism

From a series of pentanuclear, heterobimetallic complexes of the general composition [{Ln(H2O)(n)}(2){Ni(dto)(2)}(3)] center dot xH(2)O, four complexes (Ln = Gd(III) with n = 4; Ln = Dy(III), Ho(III), or Er(III), with n = 5; x = 9-12; dto = 1,2-dithiooxalate) were studied due to their large magnetic moments (up to 14.65 B.M.). The magnetic properties of these complete series were measured at room temperature and the temperature dependent magnetic properties of the complexes Gd2Ni3, Dy2Ni3, Ho2Ni3, and Er2Ni3 were studied at room temperature down to 1.8 K. Whereas the intramolecular metal-metal distances were rather long (Ni1-Ni2: 11.0-11.5 angstrom; Ln-Ni: 6.0-6.3 angstrom), relatively short intermolecular metal-metal distances (Ni1-Ni2': 3.5 angstrom; Er-Er': 6.0 angstrom) were found in the crystal lattice, giving rise to weak intermolecular metal-metal interactions. These weak spin interactions were also supported by the EPR spectrum of a powdered sample of the diamagnetically undiluted Gd2Ni3 complex. (C) 2008 Institute of Chemistry, Slovak Academy of Sciences.