Single-molecule magnet behaviour in a tetranuclear Dy^III complex formed from a novel tetrazine-centered hydrazone Schiff base ligand

Abstract

Two analogous tetranuclear lanthanide complexes have been synthesized with the general formula [Ln₄(vht)₄(MeOH)₈](NO₃)₄·aMeOH·bH₂O, where H₂vht = (3,6-bis(vanillidenehydrazinyl)-1,2,4,5-tetrazine) and Ln = Dy^III (1), Gd^III (2). These complexes are characterized by several techniques; including single-crystal X-ray diffraction, SQUID magnetometry and single-crystal micro-SQUID hysteresis loop measurements. Elucidation of the crystal structure of the complexes shows that the lanthanide ions are bridged by a tetrazine ring, a rare bridging moiety for lanthanide ions. Magnetic studies reveal that both 1 and 2 exhibit weak ferromagnetic exchange interactions between Ln ions, and 1 displaying Single-Molecule Magnet (SMM) behaviour with a magnetisation reversal barrier of U_eff = 158 K (τ₀ = 1.06 × 10^-7 s).