Synthesis and magnetic properties of μ-2-nitroterephthalato-bridged binuclear lanthanide(III) complexes

Nine new binuclear lanthanide(III) complexes described by the overall formula [Ln(2)(NTPHA)(Me(2)bpy)(4)(ClO4)(2)](ClO4)(2) (Ln = La, Nd, Sm, Eu, Gd, Tb, Dy, Ho Er), where Me(2)bpy stands for 4,4'-dimethyl-2,2'-bipyridine, and NTPHA represent, the 2-nitroterephthalate dianions, have been synthesized and characterized by elemental analyses, IR, ESR and electronic spectra, and molar conductance measurements. It is proposed that these complexes present NTPHA-bridged structures consisting of two lanthanide(III) ions. The variable-temperature magnetic. susceptibilities (4similar to300 K) of complex [Gd-2(NTPHA)(Me(2)bPy)(4)(ClO4)(2)](ClO4)(2) were measured and studied, demonstrating a very weak antiferromagnetic spin-exchange interaction between Gd(III)-Gd(III) ions within the complex. Based on the spin Hamiltonian operator, (H) over cap = -2J (S) over cap (1) . (S) over cap (2), the exchange parameter (J) was evaluated as -0.12 cm(-1).