Effect of coordinated anions on ferromagnetically coupled Dy 2 zero-field single-molecule magnets.

A new hydrazone Schiff base ligand was condensed from 2-hydroxy-3-methoxybenzaldehyde and pyrimidine-4-carbohydrazide {H 2 L = ( E )- N '-(2-hydroxy-3-methoxybenzylidene)pyrimidine-4-carbohydrazide}, which was used to assemble two new Dy 2 complexes Dy 2 L 2 (DMF) 2 (NO 3 ) 2 (1) and Dy 2 L 2 (DMF) 2 (AcO) 2 (2). Notably, the coordinated anions have a subtle effect on the coordination configurations of the Dy 3+ ions and the magnetic properties of the two Dy 2 complexes. The Dy 3+ ions in 1 and 2 have the same N 2 O 5 coordination environment but show the triangular dodecahedron and the biaugmented trigonal prism coordination configurations, respectively. Magnetic measurements revealed that both 1 and 2 have intramolecular ferromagnetic interactions between the Dy 3+ ions and show single-molecule magnet behaviors at 0 Oe, with U eff / k values of 58.2 K for 1 and 59.9 K for 2. These magnetic properties may be explained by theoretical calculations.