Determinative Effect of Axial Linearity on Single‐Molecule Magnet Performance in Dinuclear Dysprosium Complexes

Abstract

Two dichloride-bridged dinuclear dysprosium(III) complexes based on salen ligands, namely, [Dy(L 1 )(μ-Cl)(thf)] 2 (1; H 2 L 1 = N,N'-bis(3,5-di-tert-butylsalicylidene)phenylenediamine) and [Dy 2 (L 2 ) 2 (μ-Cl) 2 (thf) 2 ] 2 (2; H 2 L 2 = N,N'-bis(3,5-ditert-butylsalicylidene)ethylenediamine) are reported. These two complexes have two short DyÀ O (PhO) bonds that exhibit angles of ~90°for 1 and ~143°for 2, leading to clear slow relaxation of the magnetization for 2 and not for 1. Compound 2 has a near-identical core to the recently reported compound [Dy 2 (L 3 ) 2 (μ-Cl) 2 (thf) 2 ] (3; H 2 L 3 = N-(2pyridylmethyl)-N,N-bis(2'-hydroxy-3',5'-di-tertbutylbenzyl)amine). The only substantial difference is the relative angle of the two O (PhO) À DyÀ O (PhO) vectors, which is collinear in 2 owing to inversion symmetry and ~68°in 3 due to a molecular C 2 axis. It is shown that this subtle structural difference leads to large differences in the dipolar ground states, giving rise to open magnetic hysteresis for 3 and not for 2.

Metal–Halide Covalency, Exchange Coupling, and Slow Magnetic Relaxation in Triangular (CpiPr5)3U3X6 (X = Cl, Br, I) Clusters

“…Based on the maxima in χ M versus temperature for 1-X , the temperatures at which magnetic exchange influences the magnetic susceptibility are low enough that only the ground Kramers doublet (i.e., ± M J states) of each uranium ion will be thermally populated. , The dipolar interaction, in such a case, will involve through-space interactions between the magnetic moments of the ground Kramers doublets of each uranium ion, with the strength of the interaction decreasing with larger U···U separations, r , by the relation 1/ r 3 . Dipolar interactions dominate magnetic exchange in many multilanthanide complexes (| J dip | is typically on the order of ∼1–5 cm –1 ) and the magnitude of this exchange is strongly dependent on the orientation of the individual Kramers doublets with respect to each other. ,,− Each uranium(III) center in 1-X likely possesses strongly uniaxial magnetic anisotropy (i.e., g z > g x , g y ) as a result of the strong U–Cp i Pr bonding interaction . In the simplest scenario, each uranium ion possesses a completely axial, and maximal, M J = ± 9/2 ground state ( g x , g y , g z = 0, 0, 6.55); assuming full parallel alignment of the magnetic moments, upper limits for | J dip | for 1-Cl , 1-Br , and 1-I are 0.50, 0.44, and 0.39 cm –1 , respectively (see Supporting Information for details).…”

An alkoxyborate-bridging Dy2 single-molecule magnet with ferromagnetic coupling

“…[33][34][35][36][37][38] However, the non-zero angle between the local magnetic anisotropy axes and the associated magnetic exchange produces a QTM-facilitating transverse field and may even quench the SMM behaviour. 39,40,68 It follows that promoting appropriate magnetic coupling in these systems is of great research significance, but not an easy task.…”

Structures and Single-Molecule Magnet Behavior of Dy3 and Dy4 Clusters Constructed by Different Dysprosium(III) Salts

“…For oblate Dy III –SMMs, a strong axial crystal field (CF) and weak equatorial ligand field are required to balance the electron cloud distribution. , However, for multicore systems, the magnetic coupling is complex because of the different anisotropy of central ions. Therefore, it is of great significance to analyze the relationship between structure and magnetic properties, optimize the anisotropy of single-metal ions, and synthesize ideal structural configurations to construct Dy III SMMs with high performance. − For the development of such SMMs, the selection of suitable ligands is important. Indeed, Schiff base ligands behave as O- and N-multidentate ligands that can readily form many types of coordination pockets to coordinate with Dy III ions.…”