An Ytterbium-Pyrazine Square [(C₅H₄Me)₂Yb^III(pyz^•-)]₄ Formed by Reversible Electron Transfer and Concomitant...

Area of Science:

• Coordination Chemistry
• Materials Science
• Inorganic Chemistry

Background:

• Pyrazine (pyz) is crucial for studying electron delocalization in mixed-valent and strongly coupled materials.
• Yb(II) complexes serve as precursors in synthesizing novel coordination compounds.

Purpose of the Study:

• To synthesize a molecular square complex using a Yb(II) precursor and pyrazine.
• To investigate the metal-ligand redox cooperativity in the formation of the complex.
• To characterize the electronic and magnetic properties of the resulting Yb-pyrazine complex.

Main Methods:

• Synthesis of a Yb(II) precursor, [(C5H4Me)2YbII(THF)2] (1).
• Redox-mediated synthesis of the molecular square complex [(C5H4Me)2YbIII(pyz•−)]4·½(C7H5F3) (2).
• Characterization using structural analysis, magnetometry, vibrational spectroscopy, X-ray absorption near-edge structure (XANES) spectroscopy, and DFT calculations.

Main Results:

• Successful synthesis of the Yb-pyrazine molecular square (2) via metal-ligand redox cooperativity.
• Evidence of charge transfer from Yb(II) to pyrazine confirmed by multiple analytical techniques.
• DFT calculations assigned low-energy UV-vis bands to pyrazine-SOMO-to-metal-4f charge transfer.
• Magnetic studies revealed significant Yb-pyz•− and pyz•−-pyz•− exchange couplings.

Conclusions:

• The study demonstrates successful metal-ligand redox cooperativity in forming a Yb-pyrazine molecular square.
• The complex exhibits significant charge transfer and magnetic coupling, highlighting the role of pyrazine as a redox-active ligand.
• The findings contribute to understanding electron delocalization and magnetic interactions in Yb-based coordination materials.