Synthesis and magnetic properties of bionuclear lanthanide(III) complexes bridged by μ-2-chloroterephthalate groups

The new binuclear lanthanide(III) complexes described by the overall formula [Ln2(CTPHA)(Mephen)4(ClO4)2](ClO4)2 (Ln = La, Ce, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er), where Mephen stands for 5-methyl-1,10-phenanthroline, and CTPHA represents the 2-chloroterephthalate dianions, have been synthesized and characterized by elemental analyses, molar conductance measurements, IR, ESR and electronic spectra. It is proposed that these complexes present CTPHA-bridged structures consisting of two lanthanide(III) ions. The [Gd2(CTPHA)(Mephen)4(ClO4)2](ClO4)2 complex has ben further characterized by variable-temperature magnetic susceptibilities (4 ∼ 300 K), demonstrating a very weak antiferromagnetic spin-exchange interaction between Gd(III)-Gd(III) ions within the complex. Based on the spin Hamiltonian operator, J = -2JS1S2, the exchange parameter (J) was evaluated as -0.16 cm-1. (author)