Unprecedented redox-driven ligand ejection in nickel(II)-diiminosemiquinonate radical complexes

Area of Science:

• Inorganic Chemistry
• Coordination Chemistry
• Radical Chemistry

Background:

• Nickel complexes are crucial in catalysis and materials science.
• Polydentate ligands with radical moieties offer unique electronic and structural properties.
• Understanding ligand behavior in metal complexes is key to designing new functional materials.

Purpose of the Study:

• To synthesize and characterize nickel(II) complexes with diiminosemiquinonate radicals.
• To investigate the electrochemical and spectroscopic properties of these complexes.
• To explore the reactivity of the nickel(II) complexes, particularly ligand-metal interactions.

Main Methods:

• Synthesis of nickel(II) complexes with 1:1 and 1:2 metal-to-ligand stoichiometries.
• X-ray diffraction for structural determination.
• Visible-Near-Infrared (Vis-NIR) and Electron Paramagnetic Resonance (EPR) spectroscopy for electronic and magnetic characterization.
• Electrochemical techniques to study redox behavior.

Main Results:

• Two nickel(II) complexes, [Ni(L)] (1) and [Ni(L)2] (2), were successfully prepared.
• Structural, spectroscopic, and electrochemical data confirmed the coordination environment and radical nature.
• Oxidation of complex 1 led to ligand ejection, yielding complex 2.

Conclusions:

• The study successfully synthesized and characterized novel nickel(II) complexes with diiminosemiquinonate ligands.
• Ligand-centered oxidation is a viable pathway to modify the coordination sphere and stoichiometry.
• These findings provide insights into the redox-driven reactivity of radical-containing metal complexes.