Synthesis and Structures of Tris(cyclononatetraenyl) Rare-Earth Complexes [Ln(C₉H₉)₃] (Ln = Y, Gd, Tb, Dy, Ho, Er, Tm)

Abstract

The article reports the synthesis and structural characterization of a series of Ln(C9H9)3 complexes with the cyclononatetraenyl (Cnt, C9H9) ligand (Ln = Y, Gd, Tb, Dy, Ho, Er, Tm). The Yb and Sm complexes were not obtained and the reaction of the potassium salt of the Cnt ligand with trivalent halides salts of the corresponding metals led to the known bis-Cnt sandwich compounds, Ln(C9H9)2. The X-ray diffraction studies on the trivalent complexes show that the Cnt ligand is significantly bent in order to accommodate the large size of the ligand while keeping the aromaticity. When the size of the lanthanide ion decreases, the ligand does not switch away but swings over the metal ion in order to maximize the electrostatic interactions. The 1 H NMR and the UV-Visible spectroscopies were recorded as well as the solid-state magnetism. The UV-Visible spectroscopy highlights a remarkable charge-transfer band in the Tm complex while ligand-based transitions are principally observed with all other metal ions. The magnetic behavior of the series agrees with trivalent lanthanides ions and the computations at the CASSCF level confirm the trivalent electronic structure.

Unparalleled selectivity and electronic structure of heterometallic [LnLn′Ln] molecules as 3-qubit quantum gates

“…The electronic structures of Er and Pr were determined by means of CASSCF-SO-RASSI calculations (details in the ESI, Table S6 †) using OpenMolcas. This methodology has consistently succeeded at describing the electronic structure of lanthanides [42][43][44] and so it is well suited to address the basic aspects that make a spin-bearing center a good qubit, namely the character of the electronic ground state (wavefunction composition and g-values) and its energy separation from excited states.…”

Back to the future of organolanthanide chemistry

“…Note that the flexibility of the Cnt ligand also allows the formation of Ln(Cnt) 3 complexes (vide infra). 38 The neutral 4f-element sandwich complexes with unsubstituted aromatic ligands often suffer from poor solubility in organic solvents, which hinders both their characterization and the study of their reactivity. As such, derivatives of the versatile Cp and Cot ligands were used and constitute most of the sandwich complexes made in this area.…”

“…The corresponding synthesis was impossible for Sm or Yb but could be performed for the Tm and Y analogs. 38 The original structures of tris-Cp arrangements made in 1954 found new horizons in the most recent studies. Alongside reactivity studies, the fast development of molecules behaving as permanent magnets below a given temperature (Single Molecule Magnets, SMMs) became attractive.…”

“…Note that the flexibility of the Cnt ligand also allows the formation of Ln(Cnt) 3 complexes ( vide infra ). 38…”

“…The corresponding synthesis was impossible for Sm or Yb but could be performed for the Tm and Y analogs. 38 The original structures of tris-Cp arrangements made in 1954 found new horizons in the most recent studies.…”