An Organometallic Building Block Approach To Produce a Multidecker 4f Single-Molecule Magnet

Abstract

An organometallic building block strategy was employed to investigate the magnetic properties of a Ln III organometallic single-ion magnet (SIM) and subsequent single-molecule magnet (SMM) after coupling two of the monomeric units. New homoleptic Dy III COT″ 2 and Ln III 2 COT″ 3 (Ln = Gd, Dy) complexes have been synthesized. DFT calculations of the bimetallic Dy III complex indicate strong metal−ligand covalency and uneven donation to the Dy III ions by the terminal and internal COT″ 2− (cyclooctatetraenide) rings that correlate with the respective bond distances. Interestingly, the studies also point to a weak covalent interaction between the metal centers, despite a large separation. The ac susceptibility data indicates that both Dy III COT″ 2 and Dy III 2 COT″ 3 act as an SIM and an SMM, respectively, with complex multiple relaxation mechanisms. Ab initio calculations reveal the direction of the magnetic anisotropic axis is not perpendicular to the planar COT″ rings for both Dy III COT″ 2 and Dy III 2 COT″ 3 complexes due to the presence of trimethylsilyl groups on the COT″ rings. If these bulky groups are removed, the calculations predict reorientation of the anisotropic axis can be achieved.

Molecular single-ion magnets based on lanthanides and actinides: Design considerations and new advances in the context of quantum technologies

“…This result is well supported by ab initio calculations proving the ligand field around the Dy III ion is more equatorial than axial [81], favouring the destabilisation of the mJ = ±15/2 doublet since it corresponds to an oblate charge density distribution [77]. A similar result was obtained from studies on the sandwich complexes [K(18-crown-6)][Ln(COT)2], with Ln = Er III (17), or Dy III (18), which possess a high symmetry axis due to a parallel arrangement of the eightfold symmetry axes of individual COT ligands.…”

A base-free synthetic route to anti-bimetallic lanthanide pentalene complexes

“…Tetramethylsilane has proved to be an excellent recrystallisation solvent for complexes such as 1 which are extremely soluble in aliphatic hydrocarbons. The cocrystallised SiMe 4 in the molecular structure determined by single crystal X-ray diffraction (XRD) was lost from the bulk solid after rigorous drying in vacuo, as confirmed by microanalysis. Complex 1 was found to be diamagnetic, consistent with a ground state 4f 14 ) due to its low solubility.…”

“…Multimetallic complexes of the lanthanide metals are of interest as molecular models for lanthanide-based polymers, 1,2 which have potential applications in magnetic materials, [3][4][5][6] molecular catalysis, 7,8 and luminescent devices. [9][10][11] The aromatic ligand pentalene [C 8 H 6 ] 2− (= Pn) has shown the ability to facilitate strong electronic delocalisation in anti-bimetallic transition metal compounds, 12 and promote coupling effects through the planar π-system of the bridging Pn ligand.…”

A Structurally Characterized Organometallic Plutonium(IV) Complex

“…Metalation of 1 with 2 equiv of n ‐butyllithium in THF solution affords the intermediate 2 , which was treated with 0.45 equiv of anhydrous plutonium(III) chloride, resulting in formation of the green anionic sandwich complex Li[Pu(1,4‐COT′′) 2 ] ( 3 ). The final step, that is, oxidation to the neutral Pu IV sandwich, was inspired by our previously discovered method, which employed anhydrous CoCl 2 as a mild oxidant to convert the anionic lanthanide(III) sandwich complexes [Ln(COT′′) 2 ] − into the linear neutral triple‐decker sandwich species Ln 2 (COT′′) 3 48, 49, 50, 51. Thus, after complete removal of THF, the green‐brown residue was redissolved in toluene.…”

“…1,4‐Substitution was also found in all previously reported lanthanide half‐sandwich and sandwich complexes [(1,4‐COT′′)Ln(μ‐Cl)(THF)] 2 , [Li(THF) 4 ][Ln(1,4‐COT′′) 2 ], and [Li(DME) 3 ][Ln(1,4‐COT′′) 2 ], as well as in the triple‐decker sandwich complexes Ln 2 (1,4‐COT′′) 3 (Ln=Nd, Dy, Er) 46, 48, 49, 50, 51, 52, 56, 57, 58. However, there are a few remarkable reports in the literature that indicate the triorganosilyl groups in these bulky bis(silylated) COT ligands can migrate under certain conditions; thus far, this process is not fully understood.…”