Large Energy Barrier and Magnetization Hysteresis at 5 K for a Symmetric {Dy₂} Complex with Spherical Tricapped Trigonal Prismatic Dy^III Ions

Abstract

The introduction of the Schiff base ligand N-salicylidene-2-amino-5-chlorobenzoic acid (sacbH) in 4f-metal chemistry has afforded a new dinuclear complex, [Dy(NO)(sacbH)(HO)(MeCN)] (1), with the metal ions adopting a rare spherical tricapped trigonal prismatic coordination geometry. The deprotonated phenoxido O atoms of the organic chelate occupy the axial triangular faces of the prism and were found to be very close to the main anisotropy axes of the two Dy ions. As a result, the {Dy} compound exhibits frequency- and temperature-dependent out-of-phase ac signals below ∼25 K in the absence of a static dc field, yielding an energy barrier of 109.3(1) K for the reversal of magnetization. Fast and efficient quantum tunneling of magnetization, attributed to the strong tails of signals below ∼15 K, was suppressed through the application of a small dc field, yielding entirely visible χ″ signals below 27 K. Single-crystal magnetic hysteresis studies confirmed the single-molecule magnet (SMM) behavior of 1; the hysteresis loops appear at temperatures below ∼5 K, which is one of the highest blocking temperatures in the field of 4f-SMMs to date. This joint magneto-structural and ab initio study demonstrates the ability of more common coordination numbers (i.e., 9), but with rare coordination geometries (i.e., spherical tricapped trigonal prismatic), to promote axiality that enhances the molecular anisotropy and subsequently the magnetization dynamics of the system.

Homodinuclear {LnIII2} (LnIII = GdIII, TbIII, HoIII, and DyIII) Complexes: Field‐Induced SMM Behavior of the DyIII and TbIII Analogues

“…Thus, the complex, [K(18‐crown‐6)(THF) 2 ] [{[(Me 3 Si) 2 N] 2 (THF)Tb} 2 (µ‐η 2 :η 2 ‐N 2 )], where the lanthanide centers are connected to each other by the radical ligand [N 2 ] 3– shows an effective barrier for magnetization reversal U eff = 227 cm –1 and a blocking temperature of 14 K . Spurred by this exciting result there have been many efforts to study dinuclear complexes . While a large number of ligands have been used for assembling such complexes, ligand design that can lead to the exclusive isolation of dinuclear complexes still is an important issue.…”

Two Series of Substituent‐Group‐Directed Adipate‐Based Lanthanide Coordination Polymers: Syntheses, Structures, Photoluminescence, and Magnetism

“…Their coordination polyhedrons were analyzed by the SHAPE 2.1 program (Tables S5–S8). The Tb1 and Tb3 ions show a spherical tricapped prism coordination geometry formed by nine oxygen atoms from the 3‐ tert ‐butyl‐adipate anions, and the Tb2 and Tb4 ions display a muffin‐shaped coordination geometry constructed from nine oxygen atoms from the 3‐ tert ‐butyl‐adipate anions and the coordinated water molecules (Figure S3). The Tb–O bond lengths fall in the range of 2.277(12)–2.719(10) Å (Table S3).…”

A series of Salen‐type homodinuclear lanthanide complexes and their slow magnetic relaxation in Dy2 and Ho2

“…Besides, the Cole–Cole plots based on the frequency‐dependent AC magnetic‐susceptibility measurement in the temperature range of 8.0–20 K (Figure ) reveal an asymmetrical semicircular shape. These data can be fitted with generalized Debye model to give values of α parameter in the range of 0.09–0.23, which indicates a relatively narrow width of relaxation processes most likely due to a combination of quantum tunneling of magnetization (QTM) and thermally assisted relaxation pathways [13a, 34a]…”

“…Complex 3 shows a comparatively higher U eff among the pure Salen‐type dinuclear dysprosium SMMs. Furthermore, replacing hydrogen atoms with electron‐withdrawing atoms on the terminal Salen‐type ligands could be a comparatively straightforward way of attaining lager barriers ( U eff ), such as complex 3 , [Dy 2 (valdien) 2 (ClCH 2 OO) 2 ], [Dy 2 (valdien) 2 (Cl 2 CHCOO) 2 ]·0.5CH 3 OH, [Dy 2 (valdien) 2 ](CF 3 COCHCOCF 3 ) 2 ],[13a] . and [Dy 2 (valdien) 2 (NO 3 ) 2 ].…”

“…Moreover, the use of ab initio calculation and electrostatic analysis to explore the SMM properties of rare earth metal complexes (such as anisotropic energy barriers [ U eff ]) is also a hot topic in molecular magnetics . In a number of dilanthanide complexes, magnetic exchange interactions have been also modelled by ab initio calculations …”