Design of Dinuclear Lanthanide Complexes from N₂O₂ Donor Ligand for Single Molecule Magnets: Crystalline Architecture and Slow Magnetic Relaxation Studies

Abstract

Three new dinuclear lanthanide complexes [Ln 2 L 2 (μ 2 -benzoate) 2 (MeOH) 2 ] ⋅ 4MeOH (H 2 L = 2-Bis(2hydroxybenzyl)aminomethyl]pyridine); Ln=Nd (1), Tb (2), Dy (3)) have been synthesized and structurally characterized by single-crystal X-ray diffraction analyses. Compounds 1, 2 and 3 are isomorphous and thus the framework connectivity features are the same for all the three compounds. In the dimeric form of the complexes, each metal centre is octacoordinated with square antiprism (D 4d symmetry) geometry, which is completed by a coordinated methanol molecule. In addition, the methanol that present in the structural voids also acts as linkers of paddle-wheel like complexes. Magnetic properties of the compounds have been investigated in detail using direct-current and alternating-current susceptibility measurements. From the analysis of all three complexes, the decrease of susceptibility value at low temperatures is due to the depopulation of Stark sublevels and the existence of intramolecular antiferromagnetic interactions. In addition, complex 3 shows slow relaxation of magnetization behavior, a characteristic feature of single molecule magnets (SMMs). An effective energy barrier value (U eff ) of 38.87 K and relaxation time (τ 0 ) of 1.665 × 10 À 7 s for the magnetic relaxation process was obtained for 3. Solid state luminescence spectra for complex 2 show characteristic green emission peaks at 543 nm region having potential for applications in the solid state as light emitting diodes and photoluminescent materials.