Strategies to quench quantum tunneling of magnetization in lanthanide single molecule magnets

Abstract

Enhancing blocking temperature (TB) is one of the holy grails in Single Molecule Magnets(SMMs), as any future potential application in this class of molecules is directly correlated to this parameter....

Fluxionality Modulating the Magnetic Anisotropy in Lanthanoarene [(ηCnRn)2Ln(II/III)] (n= 4–8) Single-Ion Magnets

“…These spin−orbit states were then used to calculate the g-tensors, crystal field splitting, magnetic blocking diagram, and other magnetic properties using the SINGLE_ANISO module. 17 Both Dy(III) (11,8) have been used for Tb II (4f 8 5d 1 6s 0 /4f 8 5d 0 6s 1 ), Dy II (4f 9 5d 1 6s 0 /4f 9 5d 0 6s 1 ), and Ho II (4f 10 5d 1 6s 0 /4f 10 5d 0 6s 1 ) complexes, respectively. Here, we have taken either one 5d z 2 or one 6s orbital in our orbital space, as suggested earlier.…”

“…Single-ion magnets (SIMs) based on Dy­(III) ions are gaining attention in recent years as molecules based on dysprosocenium exhibit very high blocking temperatures, rekindling a ray of hope for potential applications such as high-dense information storage devices. , Among many types of lanthanide molecules reported, organometallic lanthanide complexes gain significant attraction as they often yield very large barrier height for magnetization reversal ( U eff ) and high blocking temperatures ( T B ). − Among these, cycloarene ligands are attractive as they generally impose very high symmetry around the metal ion, which helps to suppress the quantum tunneling of magnetization (QTM) , and offer larger crystal field splitting of m J levelsthanks to strongly delocalized π-electron clouds that readily mix with the frontier orbitals of Lanthanide (III) ions . Particularly, when the charge distribution around the Ln III ion exhibits C n ( n ≥ 7), C 5h / D 5h (for which the symmetry axis is fivefold, i.e., C 5 ), S 8 / D 4d , and S 12 / D 6d point group, the QTM is found to be quenched, and many of these points groups are accessible for cycloarene ligands. , The cycloarene ligands are not only suitable for Dy­(III) ion with an oblate electron density but also for Er­(III) ion with prolate electron density (if m J = ±15/2 is stabilized as the ground state) if the ring size is much larger . For example, among the Er­(III) SIMs, the [Er­(COT) 2 ] − (COT = cyclooctatriene) has one of the highest blocking temperatures reported (11 K, 35 Oe/s sweep rate). , Thus, the marriage of a suitable metal ion with an appropriate cycloarene is of utmost importance for attaining large blocking temperatures.…”

“…10 Particularly, when the charge distribution around the Ln III ion exhibits C n (n ≥ 7), C 5h /D 5h (for which the symmetry axis is fivefold, i.e., C 5 ), S 8 / D 4d , and S 12 /D 6d point group, the QTM is found to be quenched, and many of these points groups are accessible for cycloarene ligands. 11,12 The cycloarene ligands are not only suitable for Dy(III) ion with an oblate electron density but also for Er(III) ion with prolate electron density (if m J = ±15/2 is stabilized as the ground state) if the ring size is much larger. 13 For example, among the Er(III) SIMs, the [Er(COT) 2 ] − (COT = cyclooctatriene) has one of the highest blocking temperatures reported (11 K, 35 Oe/s sweep rate).…”

“…Similar to Ln(III), for Ln(II) complexes, an ANO-RCC-TZVP level of basis set for the Ln(II) ion and ANO-RCC-DZV basis set for other atoms have been used to perform CASSCF/RASSI-SO/SINGLE_ANISO calculations. Extended active space of CAS-(9,8), CAS- (10,8), and CAS- (11,8) have been used for Tb II (4f 8 5d 1 6s 0 /4f 8 5d 0 6s 1 ), Dy II (4f 9 5d 1 6s 0 /4f 9 5d 0 6s 1 ), and Ho II (4f 10 5d 1 6s 0 /4f 10 5d 0 6s 1 ) complexes, respectively. Here, we have taken either one 5d z 2 or one 6s orbital in our orbital space, as suggested earlier.…”

Improving the performance of β-diketonate-based DyIII single-molecule magnets displaying luminescence thermometry

“…That is because the slightly-distorted D 4d pseudo-symmetry of the Dy III polyhedron enables a considerable separation of the KDs arising from the Dy III 6 H 15/2 ground state, as highlighted by luminescence, which should minimize the transverse CF terms, minimizing the QTM relaxation. 14 Furthermore, the long Dy–N bonds in 1 should also contribute to decrease the transverse CF terms, enhancing the U eff . 2 This effect is a consequence of the nearby non-coordinated nitrogen atoms imparting electron-withdrawing effects on the coordinated nitrogen atoms, which lengthens the Dy–N bonds.…”