The First {Dy₄} Single-Molecule Magnet with a Toroidal Magnetic Moment in the Ground State

Abstract

A toroidal magnetic moment in the absence of a conventional total magnetic moment was first observed in a novel tetranuclear dysprosium cluster with nonmagnetic ground state. The toroidal state is quite robust with respect to variations of the exchange parameters. W ith consideration of the potential applications in new storage and information-processing technologies, the researches on single-molecule magnets (SMMs) are recognized as an important area for molecular magnetism.1 Thanks to the large intrinsic magnetic anisotropy of lanthanide (Ln) ions, remarkable efforts have been focused on the pure 4f SMMs and single-ion magnets (SIMs) in recent years.2−7 For the SMMs incorporating multiple Ln ions, though weak magnetic interactions, the very large anisotropy favors the orientation of magnetization along an easy axis. The anisotropic barrier of an SMM is derived from a combination of both the single ionic anisotropy and exchange interaction in these complexes, 3b,6b while the zero-field splitting on Ln sites is much larger than the exchange splitting. Dy III is one of the most attractive heavy rareearth ions showing the following unique features: first, Dy III ions will always maintain a high-magnitude ±m J quantum number and a doubly degenerate ground state (ground Kramers' doublet) because of its odd electron count; second, a relatively large separation between the bistable ground state and the first excited state relaxes the spin much slower. Since the first case was revealed in the famous {Dy 3 } triangle, detection of the other lanthanide molecular species with toroidal magnetic moments has become an interesting topic of lanthanide-based SMM chemistry.2,3 The noncollinearity of the single-ion easy axes of magnetization of the Dy III ions leads to a nonmagnetic ground state, giving rise to the toroidal magnetic moments on the Dy III sites and also the slow relaxation behavior.6 Herein we report a novel {Dy 4 } SMM, [Dy 4 (μ 3 -OH) 2 (μ-OH) 2 (2,2-bpt) 4 (NO 3 ) 4 (EtOH) 2 ] [1; 2,2-bptH = 3,5-bis(pyridin-2-yl)-1,2,4-triazole], which is the first case of the {Dy 4 } family with a toroidal magnetic moment in the ground state.Colorless brick crystals of 1 were obtained from solvothermal reactions of Dy(NO 3 ) 3 ·5H 2 O with 2,2-bptH in the presence of triethylamine. Notably, the bpt − ligand with two bidentate chelating sites is, for the first time, used to produce Ln

The High‐Order Toroidal Moments and Anapole States in All‐Dielectric Photonics

“…After detracing and symmetrization of the primitive Cartesian multipoles, the residual terms form a set of irreducible toroidal moments limited by the toroidal electric octupole and toroidal magnetic quadrupole (Table ). The first order toroidal electric dipole considered previously in a plenty of papers is derived from the decomposition of the primitive electric octupole and the primitive magnetic quadrupole ; the fourth order of the primitive Cartesian multipoles produces two toroidal multipole moments—the toroidal magnetic dipole T ( m ) and the toroidal electric quadrupole (TEQ) , which are obtained from the magnetic octupole and the electric 16‐pole ; the decomposition of the primitive electric 32‐pole and magnetic 16‐pole produces the second contributing term to the full electric dipole moment, the toroidal magnetic quadrupole , and the toroidal electric octupole . The detailed derivation is given in the Supporting Information.…”

Coupling Dy3 Triangles to Maximize the Toroidal Moment

“…[4] Particularly relevant to these endeavors is the consideration of bounded (confined) metal oxide structures having toroidal moments compared with their solid-state infinite analogues. [1c, 8] Subsequently, a Dy 4 single-molecule magnet (SMM), [9] a Dy 6 -1 SMM, [10] and a heterometallic Cu II /Dy 3 III 1D polymer (Dy 3 Cu) [4c] have been reported to show a toroidal magnetic moment in the ground state. [6] The recently investigated Dy 3 triangle (prototype Dy 3 ) [7] is one of the four possible ingredients for creating multiferroic systems that should manifest two or more out of ferroelectric, ferromagnetic, ferroelastic, and ferrotoroidal behavior.…”

Single-Molecule Toroics and Multinuclear Lanthanide Single-Molecule Magnets

“…This allows us to design a target molecule-based system with specific properties and functions, including the one with desired noncollinear arrangement of magnetic moments corresponding to toroidal magnetization. In fact, such molecules have been reported in SMM field with several typical examples of Dy 3 triangles [5,13], planar Dy 4 [14] and cyclic Dy 6 [15] showing the toroidal moment at ground state, as revealed by ab initio calculations. In particular, the non-magnetic ground state in the seminal Dy 3 SMMs reported by A.K.…”

“…This is the first reported SMM that demonstrates a dielectric transition between a paraelectric phase and a ferroelectric phase. [14]. Notably, the compound was assembled from a rigid multiple nitrogen-ligand with two bidentate chelating sites (Fig.…”