Syntheses, structures, and magnetic properties of homodinuclear lanthanide complexes based on dinucleating Schiff base ligands.

The first two families of homodinuclear lanthanide(III) complexes, formulated as [(L(OEt))2Ln2(L1)] and [(LOEt)2Ln2(L2)] (Ln(3+) = Dy(3+), Tb(3+), Ho(3+), Gd(3+), and Y(3+); L1(4-) = 2,2',2'',2'''-[1,2,4,5-benzenetetrayltetrakis(nitrilomethylidyne)]tetrakisphenolate; L2(4-) = 2,2',2'',2'''-[[1,1'-biphenyl]-3,3',4,4'-tetrayltetrakis(nitrilomethylidyne)]tetrakis(4-chlorophenolate); L(OEt)(-) = (η(5)-cyclopentadienyl)tris(diethylphosphito-p)cobaltate(III)), were successfully synthesized based on Kläui's tripodal building block NaL(OEt) and two dinucleating Schiff base ligands, H(4)L1 and H(4)L2, respectively. Single-crystal X-ray analyses show that these lanthanide complexes have two seven-coordinated metal binding sites, linked to each other with a phenyl or biphenyl bridge. Variable temperature dc magnetic measurements reveal the weakly antiferromagnetic coupling between paramagnetic lanthanide ions, while ac magnetic data exhibit the field-induced relaxation of magnetization for the corresponding Dy2 complexes 1 and 6. A further magnetic dilution study for 1 suggests that the slow magnetic relaxation originates from the single-ion magnetic behaviour of Dy(3+) ions.