Redox- and EPR-Active Graphene Diiron Complex Nanocomposite

Area of Science:

• Materials Science
• Nanotechnology
• Coordination Chemistry

Background:

• Graphene's unique electronic properties make it an attractive platform for functionalization.
• Anchoring metal complexes onto nanomaterials can create novel hybrid materials with tailored functionalities.
• Mixed valence diiron complexes are of interest for their catalytic and electronic properties.

Purpose of the Study:

• To covalently anchor a mixed valence diiron(II/III) complex with the 2,6-bis{bis[(2-pyridinylmethyl)amino]methyl}phenol (bppH) ligand onto graphene.
• To characterize the resulting functionalized graphene material and its diiron complexes.
• To investigate the electronic and redox properties of the grafted diiron complex.

Main Methods:

• Microwave-assisted diazonium coupling for in situ covalent anchoring of the bppH ligand onto graphene.
• Complexation with iron(II) in the presence of dioxygen to form the dinuclear iron complex.
• Characterization using X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), cyclic voltammetry (CV), scanning transmission electron microscopy (STEM), energy-dispersive X-ray spectroscopy (EDX), and electron paramagnetic resonance (EPR) spectroscopy.

Main Results:

• Successful covalent anchoring of the bppH ligand onto graphene was confirmed by multiple spectroscopic techniques.
• Semiquantitative XPS analysis indicated a high loading of bppH ligand (0.33 mmol/g, 20.7 wt%).
• EPR spectroscopy revealed distinct spin centers associated with the graphene lattice (S = 1/2) and the iron(III) center (S = 5/2).
• Electrochemical studies demonstrated redox activity of the grafted complex with accessible FeII/FeIII and FeIII/FeIV redox processes.
• An estimated surface coverage of 58 pmol cm-2 was determined from electrochemical measurements.

Conclusions:

• A novel graphene-supported diiron complex was successfully synthesized and characterized.
• The hybrid material exhibits unique electronic properties due to the interplay between the graphene lattice and the anchored complex.
• The demonstrated redox activity and high surface coverage suggest potential applications in catalysis and electronic devices.