Ambivalent binding between a radical-based pincer ligand and iron.

Area of Science:

• Coordination Chemistry
• Inorganic Chemistry
• Materials Science

Background:

• Exploration of redox-active ligands for novel electronic properties.
• Iron complexes with pincer-type ligands are of interest due to their diverse applications.

Purpose of the Study:

• To synthesize and characterize a novel iron complex with a redox-active pincer-type ligand.
• To investigate the electronic structure, magnetic properties, and valence delocalization in the complex.

Main Methods:

• Synthesis of the iron complex via two distinct routes.
• Electrochemical studies, UV-Vis absorption, and diffuse reflectance spectroscopy.
• X-ray crystallography, Mössbauer spectroscopy, and magnetic susceptibility measurements.
• Density Functional Theory (DFT) calculations.

Main Results:

• Successful preparation of the iron complex exhibiting valence delocalization.
• Identification of an isolated S = 5/2 ground spin state.
• Low-temperature magnetic behavior dominated by intermolecular exchange interactions.
• DFT calculations confirm strong electronic interactions and electron density delocalization.

Conclusions:

• The synthesized iron complex demonstrates significant valence delocalization due to strong metal-ligand electronic interactions.
• The observed magnetic properties are attributed to the isolated spin state and intermolecular exchange.
• The findings highlight the challenges in assigning formal oxidation states in such redox-active systems.