Fine-Tuning Ligand to Modulate the Magnetic Anisotropy in a Carboxylate-Bridged Dy₂ Single-Molecule Magnet System

Abstract

A series of dinuclear Dy(III) compounds with the general formula [Dy2(μ2-anthc)4(anthc)2(L)2] (anthc(-) = 9-anthracenecarboxylate, L = 2,2'-bipyridyl (1), 1,10-phenanthroline (2), and 4,7-dimethyl-1,10-phenanthroline (3)) were synthesized and magnetically characterized. These compounds exhibit single-molecule magnet (SMM) behavior in the absence of the direct-current field, which is rarely observed for carboxylate-bridged dinuclear Dy2 system. With the first coordination sphere of Dy(III) centers being fixed, the energy barrier was modulated by sequentially modifying the terminal neutral L ligands in this Dy2 system. Theoretical calculations revealed that the symmetry of the charge distribution surrounding the Dy(III) centers in 1-3 is the decisive factor to determine the relaxation of the SMMs. The combination of the larger charge distribution along the magnetic axis and lower charge distribution in the equatorial plane (hard plane) formed by five coplanar coordination atoms including two N atoms provided by an L ligand led to a strong easy-axis ligand field in these compounds. This work presents a rational method to modulate the dynamic magnetic relaxation of the lanthanide SMMs through fine-tuning electrostatic potential of the atoms on the hard plane.

Tuning the Magnetic Interactions in Dy(III)4 Single-Molecule Magnets

“…[27][28][29] Although difficult, it has been showed that the magnetic interactions are extremely sensitive to the subtle variations of the local coordination sphere and the ligand field around the dysprosium (III) ion. [30][31] A current challenge, therefore, is to assemble targeted polynuclear dysprosium (III) 4 SMMs, thereby providing a means of tuning the magnetic interactions through the influence of different coordination environments around the metal site.…”

An Unusual LnIII‐Based Metal‐Organic Framework with Dinuclear Nodes Exhibiting Single‐Molecular Magnet Behavior

“…The example of 1 clearly shows a Dy 2 node with potential to be an SMM actually showing the SMM property in the MOF. Similar Dy 2 units have been reported to be SMMs but they often have monoatomic oxygen bridges from syn, anti ‐carboxylate bridging groups and chelating bpy or phen ligands . In fact researchers have shown that these chelating ligands can be used to fine tune the crystal field and have a large effect in the SMMs properties of the Dy 2 unit.…”

Dinuclear LnIII Complexes with 9‐Anthracenecarboxylate Showing Field‐Induced SMM and Visible/NIR Luminescence

“…On the other hand, chelating ligands could block two or three coordination sites per Ln III ion, thereby preventing potential polymerization . For this purpose, N‐donor species such as 2,2′‐bipyridine, 1,10‐phenanthroline, or 2,2′:6′,2′′‐terpyridine are ideal candidates …”

“…The crystal structure of the analogous lanthanum complex [La 2 (µ 2 ‐9‐AC) 4 (9‐AC) 2 (bpy) 2 ] has previously been published . Moreover, recently, Zhang and Liu and co‐workers reported the analogous dysprosium SMM compound [Dy 2 (µ 2 ‐9‐AC) 4 (9‐AC) 2 (bpy) 2 ] in order to study the magnetic dependence on the variation of the chelating N‐donor ligand . We wished to expand on these previous works by using other lanthanide ions in the search for multifunctional complexes displaying magnetic and luminescent properties.…”