Anion-dependent dysprosium(iii) cluster single-molecule magnets

Abstract

A new Schiff base ligand, which is formed by the condensation reaction of 5-fluorosalicylaldehyde and pyrimidine-4-carbonyl hydrazide {H₂L_Schiff = (E)-N′-(5-fluoro-2-hydroxybenzylidene)pyrimidine-4-carbohydrazide}, was made to react with different dysprosium(III) salts in an alkaline solution to assemble Dy₄ and Dy₆ cluster complexes, [Dy₄(OH)₂(L_Schiff)₄(H₂O)₂(NO₃)₂]·4MeCN·MeOH (1) and [Dy₆(CO₃)₂(L_Schiff)₆(H₂O)₃(MeOH)Cl₂]·5MeOH (2), depending on whether the anion used is nitrate or chloride. Complex 1 corresponding to the nitrate anion is a butterfly-like Dy₄ cluster complex with four different Dy(III) coordination configurations of [O₆N₂], [O₈N], [O₇N₂] and [O₆N₃]; when the anion is replaced by the chloride anion, carbon dioxide can be automatically captured from the air and converted into a carbonate bridging ligand, and the final product obtained is complex 2, which is a triangular prism-type Dy₆ cluster complex with double μ₃-carbonate bridging ligands. Both 1 and 2 show good zero-field SMM properties, with U_eff/k values of 116.5 K for 1 and 150.9 K for 2.