Tetraanionicarachno‐Carboranyl Ligand Imparts Strong Axiality to Terbium(III) Single‐Molecule Magnets

Abstract

A family of fully sandwiched arachno‐lanthanacarborane complexes formulated as {η6‐[μ‐1,2‐[o‐C6H4(CH2)2]‐1,2‐C2B10H10]2Ln}{Li5(THF)10} (Ln=Tb, Dy, Ho, Er, Y) is successfully synthesized, where the “carbons‐adjacent” carboranyl ligand (arachno‐R2‐C2B10H104−) bears four negative charges and coordinates to the central lanthanide ions using the hexagonal η6C2B4 face. Thus, the central lanthanide cations are pseudo‐twelve‐coordinate and have an approximate pseudo‐D6h symmetry or hexagonal‐prismatic geometry. As the crystal field effect imparted by this geometry is still unknown, we thoroughly investigated the magnetic properties of this series of complexes and found that the crystal field imposed by this ligand causes a relation of Tb>Dy>Ho>Er for the energy gaps between the ground and the first excited states, which is of striking resemblance to the ferrocenophane and phthalocyanine ligands although the latter two ligands give disparate local coordination geometries. Moreover, the effective energy barrier to magnetization reversal of 445(10) K, the observable hysteresis loop up to 4 K and the relaxation time of the yttrium‐diluted sample reaching 193(17) seconds at 2 K under an optimized field for the Tb analogue of this family of arachno‐lanthanacarborane complexes, render a new benchmark for Tb3+‐based single‐molecule magnets.

Halobenzene Adducts of a Dysprosocenium Single-Molecule Magnet

“…The 13 C{ 1 H} NMR spectra of 2-Y, 3-Y, 4-Y, and 5-Y all showed coupling of 13 C nuclei in Cp R rings with 100% abundant I = 1/2 89 Y nuclei; in some cases, these coupling constants were resolved as doublets with 1 J CY values of 1.7−1.9 Hz. In the 19 [Al{OC(CF 3 ) 3 } 4 ] − anion resonance, with an increasing impact on both the paramagnetic shift and broadening with halogen size (δ F , fwhm: 2-Dy: −82.5 ppm, υ 1/2 ≈ 180 Hz; 3-Dy: −87.7 ppm, υ 1/2 ≈ 340 Hz; 4-Dy: −89.5 ppm, υ 1/2 ≈ 380 Hz; 5-Dy: −74.19 ppm, υ 1/2 ≈ 140 Hz). Single-Crystal X-ray Diffraction.…”

Mononuclear Lanthanide Complexes in Triangular Dodecahedron Geometry: Manifestation of Single Ion Magnet Behavior for DyIII Analogue

“…The coordination of two such monoanionic ligands (L NO2 – ) along with the halide ion can generate hepta-coordination around the Ln III center. It is well-documented that complexes with high symmetry such as D 6h , D 5h , D 4h , D 4d , D ∞ , and S 8 are promising candidates for constructing molecular magnets with high performance as the higher symmetries prevent the mixing of wave functions and thereby quench the QTM. − Accordingly L NO2 H reacts with LnCl 3 •6H 2 O (Ln = Dy III , Er III ) in the presence of triethylamine to yield mononuclear complexes [Dy III (L NO2 ) 2 (Cl)­(H 2 O)]•H 2 O ( 1 ) and [Er III (L NO2 ) 2 (Cl)­(CH 3 OH)]•2CH 3 OH ( 2 ). However, in these complexes Ln III centers are eight coordinated due to an additional coordination from water in complex 1 and MeOH in complex 2 (Scheme- ).…”

Alkali metal-linked triangular building blocks assemble a high-nucleation lanthanoid cluster based on single-molecule magnets

“…In 2022, Zheng et al. used carborane ligands to coordinate with rare earth ions to construct a series of rare earth metal-organic complexes; the terbium complexes performed better, becoming a new benchmark for Tb(III)-based SMMs ( Jin et al., 2022 ). In the same year, they synthesized three examples of pentagonal bipyramid configuration Dy(III)-based SMMs by fixing the planar ligand and the balance anion unchanged and gradually fluorinating the axial alcohol-oxygen ligand ( Ma et al., 2022 ).…”

“…To design SMMs based on mononuclear complexes with superior performance and special magnetic behavior, the ligand field strength and topology of these complexes are controlled despite the metal center coordination configuration ( Woodru et al., 2013 ; Guo et al., 2018a ; Goodwin et al., 2017 ; Ding et al., 2016 ; Jin et al., 2022 ; Ma et al., 2022 ; Huang et al., 2020 ; Zhang et al., 2020 ; Zhu et al., 2021 ; Ling et al., 2022 ; Liu et al., 2018 ; Guo et al., 2018a , 2018a ; Yu et al., 2022 ). However, developing effective strategies to break through the tremendous progress achieved in SMMs based on mononuclear complexes remains difficult ( Zhang et al., 2020 ; Zhu et al., 2021 ; Ling et al., 2022 ; Liu et al., 2018 ; Lu et al, 2022 ).…”