(α-Diimine)tricarbonylhalorhenium complexes: the oxidation side

Area of Science:

• Inorganic Chemistry
• Electrochemistry
• Organometallic Chemistry

Background:

• Rhenium carbonyl complexes with α-diimine ligands are known for their electrocatalytic potential.
• Understanding the electrochemical behavior of these complexes is crucial for designing new catalysts.

Purpose of the Study:

• To reinvestigate the electrochemical behavior of [Re(CO)3X(α-diimine)] complexes, specifically focusing on the chloro and bromo derivatives.
• To elucidate the electronic and structural changes associated with the oxidation and reduction processes of these rhenium complexes.

Main Methods:

• Cyclic voltammetry was employed to study the redox properties.
• Infrared (IR) and UV-vis spectroelectrochemistry were used to monitor spectral changes during electrochemical reactions.
• Density Functional Theory (DFT) calculations were performed to support experimental findings and investigate electronic structures.

Main Results:

• Reduction of the complexes leads to halide loss, a key step for electrocatalytic activity.
• A reversible oxidation was observed for the chloro complex ([Re(CO)3Cl(α-diimine)]).
• Spectroelectrochemical and DFT results indicate significant changes in carbonyl stretching frequencies and electronic transitions upon oxidation, with calculated large g anisotropy explaining the lack of EPR signals.

Conclusions:

• The chloro rhenium complex exhibits unique reversible oxidation behavior.
• DFT calculations provide valuable insights into the electronic structure and redox mechanisms, complementing experimental spectroelectrochemical data.
• The findings contribute to a deeper understanding of redox-active rhenium complexes for potential applications in catalysis.