Mixed-Valence Aryloxido-Bridged Dilanthanide Complexes with Lanthanide-Dependent Electron Delocalization

Area of Science:

• Coordination Chemistry
• Organometallic Chemistry
• Magnetochemistry
• Lanthanide Chemistry

Background:

• Mixed-valence lanthanide complexes with Ln-Ln bonding can display strong magnetic coupling and axial magnetic anisotropy.
• Previous studies focused on iodide-bridged systems, necessitating exploration of other bridging ligands.

Purpose of the Study:

• To synthesize and characterize novel aryloxido-bridged mixed-valence dilanthanide complexes.
• To investigate the structural and magnetic properties of these new complexes, focusing on valence delocalization/localization and magnetic exchange interactions.

Main Methods:

• Synthesis of (Cp^iPr5)₂Ln₂(OAr^tt)₃ complexes (Ln = Gd, Dy).
• Solid-state structural analysis using X-ray diffraction.
• Magnetic susceptibility measurements (static and variable-temperature).
• Solid-state Raman spectroscopy.
• Computational analyses (density functional theory).

Main Results:

• Distinct solid-state structures observed: 1-Dy shows a short Dy-Dy bond (3.265(1) Å) suggesting valence delocalization, while 1-Gd exhibits an asymmetric structure indicative of valence localization.
• Magnetic data confirm valence localization in 1-Gd with weak antiferromagnetic Gd^II-Gd^III exchange.
• 1-Dy displays strong magnetic coupling, forming a large angular momentum ground state with magnetic blocking below 40 K.
• Raman spectra and computational studies indicate persistent Dy-Dy bonding in 1-Dy, influenced by structural asymmetry and vibronic coupling.

Conclusions:

• Aryloxido-bridged mixed-valence dilanthanide complexes exhibit tunable structural and magnetic behaviors.
• The Dy-Dy bonding and strong magnetic coupling in 1-Dy are crucial for its magnetic properties.
• Structural asymmetry and vibronic coupling play significant roles in valence localization at elevated temperatures in 1-Dy.