Chemistry, an Asian journal | 2019
Single-Molecule Magnetism in Three Dy2 Complexes from the Use of a Pentadentate Schiff Base Ligand and Different Benzoates.
Abstract
Three dinuclear DyIII complexes of formulae [Dy2L2(O2CPh)2]·2MeOH (1), [Dy2L2{(2-NO2)O2CPh}2] (2), and [Dy2L2{(2-OH)O2CPh}2]·MeOH·MeCN (3) (H2L = N1,N3-bis(4-chlorosalicyladehyde)diethylenetriamine) have been synthesized and structurally characterized. Complexes 1-3 possess similar Ln2 cores and differ in the substituents at the benzyl rings of benzoates. Dc magnetic susceptibility studies in the 2-300 K range showed weak antiferromagnetic interactions between two DyIII ions in 1-3. The alternating current (ac) magnetic susceptibility measurements indicated that they all exhibit SMM behavior. The strategic attachment of -NO2 group (in 2) and -OH functionality (in 3) on the skeleton of the benzoic acid led to the subtle variations of the bond lengths and bond angles in the coordination environments of the central DyIII ions, consequently resulting in the enhancement of the energy barriers for 2 and 3. Complete-active-space self-consistent field (CASSCF) calculations were employed to rationalize the experimental outcomes. The theoretical calculations confirm the existences of antiferromagnetic interactions in 1-3, and the calculated dc magnetic susceptibility data agree well with the experimental ones. The computational results reveal more axial g tensors as well as higher first excited Kramers doublets in 2 and 3, thus resulting in higher energy barriers in compounds 2 and 3.