Authors: Dawei Li | Man-Man Ding | Yuan Huang | David Felipe Tello Yepes | Haiyan Li | Yahong Li | Yi‐Quan Zhang | Jinlei Yao
Source: Dalton Transactions (article, 2020-11-17)
Field: Materials Science — Electronic, Optical and Magnetic Materials

Evolution from a single relaxation process to two-step relaxation processes of Dy<sub>2</sub> single-molecule magnets <i>via</i> the modulations of the terminal solvent ligands To explore the influences of magnetic interactions on the relaxation dynamics of single-molecule magnets (SMMs) and to understand the relationship between single-ion relaxation and the relaxation of a molecular entity, it is very important to design dinuclear lanthanide-based SMMs with two-step relaxation processes. Here, three Dy<sub>2</sub> complexes of compositions [Dy<sub>2</sub>(L)<sub>2</sub>(NO<sub>3</sub>)<sub>2</sub>(MeOH)<sub>2</sub>] (1), [Dy<sub>2</sub>(L)<sub>2</sub>(NO<sub>3</sub>)<sub>2</sub>(EtOH)<sub>2</sub>] (2), and [Dy<sub>2</sub>(L)<sub>2</sub>(NO<sub>3</sub>)<sub>2</sub>(DMF)<sub>2</sub>]·0.5EtOH (3) (H<sub>2</sub>L = 2-(((2-hydroxy-3-methoxybenzyl)imino)methyl)-4-methoxyphenol) were successfully synthesized via elaborately introducing different terminal solvent ligands. X-ray single-crystal diffraction analyses revealed that complexes 1-3 are isostructural. The two Dy<sup>III</sup> ions of 1 and 2 both adopt D<sub>2d</sub> symmetry, while the two Dy<sup>III</sup> centres of 3 display D<sub>2d</sub> and D<sub>4d</sub> symmetries, respectively. The magnetic property studies of 1-3 indicated that all three complexes exhibit single-molecule magnet (SMM) behaviours with energy barriers of 104 K for 1, 98.94 K for 2, and 76.28 K and 45.54 K for 3 under zero dc field. The target of assembling Dy<sub>2</sub> SMMs with two-step relaxation processes was achieved by gradually increasing the sizes of the terminal solvent ligands. Complex 3 exhibits two-step relaxation processes. Complete active space self-consistent field (CASSCF) calculations were performed on 1-3 to rationalize the observed differences in the magnetic behaviour. It is found that both the angles θ between the magnetic axis and the vector connecting two Dy<sup>III</sup> ions and the symmetries of Dy<sup>III</sup> ions are vital factors that affect the energy barriers of 1-3. The high local symmetries of the central metals in 1 and 2 make the complexes act as SMMs with higher energy barriers, while the smaller θ angle and different symmetries of the two Dy<sup>III</sup> ions render complex 3 as a SMM with a two-step relaxation process. This work demonstrates a new methodology for preparing SMMs with two-step relaxation processes by fine-tuning the terminal solvent ligands. Relaxation (psychology) ; Terminal (telecommunication) ; Solvent ; Magnet ; Molecule ; Magnetic relaxation ; Materials science ; Crystallography ; Process (computing) ; Single-molecule magnet ; Chemical physics ; Chemistry ; Physical chemistry ; Computational chemistry ; Organic chemistry ; Magnetization ; Physics ; Computer science ; Magnetic field ; Mechanical engineering ; Engineering Magnetism in coordination complexes ; Lanthanide and Transition Metal Complexes ; Advanced NMR Techniques and Applications