Cerium-quinone redox couples put under scrutiny

Area of Science:

• Organometallic Chemistry
• Inorganic Chemistry
• Materials Science

Background:

• Cerium complexes are versatile precursors in inorganic synthesis.
• Understanding the reactivity of cerium complexes with organic molecules is crucial for developing new catalytic systems and materials.
• 1,4-quinones are important redox-active organic compounds with diverse applications.

Purpose of the Study:

• To investigate the reactivity of homoleptic cerous complexes with various 1,4-quinones in non-aqueous solutions.
• To characterize the resulting cerium-quinone adducts using a range of analytical techniques.
• To explore the redox behavior of these complexes and their interactions.

Main Methods:

• Synthesis and characterization of homoleptic cerous complexes.
• Reaction of cerous complexes with different 1,4-quinones (DDQ, Cl4BQ, tBu2BQ, Me4BQ).
• Structural and spectroscopic analyses including X-ray diffraction, NMR, DRIFT, UV-Vis spectroscopy, and cyclic voltammetry (CV).

Main Results:

• Strongly oxidizing quinones (DDQ, Cl4BQ) yielded hydroquinolato-bridged ceric complexes.
• Less oxidizing quinones (tBu2BQ) formed redox equilibria, with bridged ceric form stable only in solid state.
• Weakly oxidizing quinones (Me4BQ) afforded cerous semiquinolates.
• Electrochemical reduction products were mimicked by chemical reduction.

Conclusions:

• The outcome of cerium-quinone reactions is highly dependent on the redox potential of the quinone.
• The study provides insights into the formation of novel cerium-quinone complexes with varying oxidation states and structures.
• The characterized complexes demonstrate potential for applications in redox chemistry and materials science.