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)(2)Ln(2)(L1)] and [(L-OEt)(2)Ln(2)(L2)] (Ln(3+)= Dy3+, Tb3+, Ho3+, Gd3+, and Y3+; 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(nitrilo-methylidyne)] tetrakis(4-chlorophenolate); L-OEt-= (eta(5)-cyclopentadienyl)tris(diethylphosphito-p)cobaltate(III)), were successfully synthesized based on Klaui's tripodal building block NaLOEt 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 Dy-2 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 Dy3+ ions.