Mononuclear Dysprosium(III) Complexes with Triphenylphosphine Oxide Ligands: Controlling the Coordination Environment and Magnetic Anisotropy

Abstract

Abstract:We report the synthesis, structural and magnetic characterization of five mononuclear Dy III ion complexes using triphenylphosphine oxide as a monodentate ligand. 4 Cl 2 ](FeCl 4 ) (5). These complexes are characterized using single crystal X-ray diffraction, which revealed that each complex has a unique coordination environment around the Dy III ion, which results in varying dynamic magnetic behavior. Ab initio calculations are performed to rationalize the observed magnetic behavior and to understand the effect that the ligand and coordination geometry around the Dy III ion has on the single-molecule magnet (SMM) behavior. In recent years, seven coordinate Dy III complexes possessing pseudo~D 5h symmetry are found to yield attractive blocking temperatures for the development of new SMM complexes. However, here we show that the strength of the donor ligand plays a critical role in determining the effective energy barrier and is not simply dependent on the geometry and the symmetry around the Dy III ion. Seven coordinate molecules possessing pseudo D 5h symmetry with strong equatorial ligation and weak axial ligation are found to be inferior, exhibiting no SMM characteristics under zero-field conditions. Thus, this comprehensive study offers insight on improving the blocking temperature of mononuclear SMMs.

Single-Ion Magnet and Photoluminescence Properties of Lanthanide(III) Coordination Polymers Based on Pyrimidine-4,6-Dicarboxylate

“…Moreover, the non spherical orbitals shape of lanthanides requires specific coordination sites in order to reduce or minimize electrostatic repulsions and stabilize the ligand field. In this way, the oblate Dy(III) ion requires the coordination of the ligands in axial positions instead of the equatorial positions to achieve high performance SMM [56]. Herein, all the studied compounds can be regarded as spherical capped square antiprism polyhedra, which possess donor atoms in both equatorial and axial positions.…”

An Inconspicuous Six-Coordinate Neutral DyIII Single-Ion Magnet with Remarkable Magnetic Anisotropy and Stability

“…Seven-coordinate complexes, possessing oblate Dy III ions in a D 5 h symmetry, proved good systems that exhibit high effective energy barrier, moderate blocking temperature, and good stability. − From these geometries, the decrease of the in-plane CNs (i.e., octahedral or trigonal bipyramid architectures) combined with extremely weak donors contributes to a reduction of the transverse CF, which may lead to Dy III complexes with ideally pure M J states and significant improvement in uniaxial magnetic anisotropy. Among, the six-coordinate complex, with the usually normal CN, is the limiting case to obtain stable low-coordinate Dy III SMMs. − Besides, the weak nonaxial ligands are expected to be symmetrically disposed on a regular polygon to suppress transverse CF components . Nevertheless, it is not easy to engineer a six-coordinate Dy III complex possessing a highly axial CF, which requires the employment of bulky ligands to force an oblate coordination environment by steric hindrance and geometrical constraints.…”

Tuning the Ferrotoroidic Coupling and Magnetic Hysteresis in Double‐Triangle Complexes {Dy3MIIIDy3} via the MIII‐linker

“…However, while TA‐QTM may be a source of temperature‐dependent magnetic relaxation, the first‐excited KDs are too high in energy to fully explain the relaxation observed at such low temperatures as 2 K. Also, similar ac susceptibilities can be obtained from complexes with contrasting first‐excited KD energies (different energies due to changes in M, e. g. 120 cm −1 ( 1’ ) vs. 90 cm −1 ( 5’ ), or coordination of ‐NO 3 vs. ‐Cl, as seen [22] in Dy III single‐ion magnets). This implies other relaxation mechanisms are taking place, such as Raman processes caused by spin‐phonon coupling, intra‐/intermolecular interactions, hyperfine couplings to nuclear spins in 161 Dy/ 163 Dy/ligands, etc.…”