Mixed Valency in a 3D Semiconducting Iron-Fluoranilate Coordination Polymer

Area of Science:

• Materials Science
• Inorganic Chemistry
• Crystallography

Background:

• Coordination polymers offer tunable structures and properties.
• Interpenetrating networks present unique structural motifs.
• The fluoranilate ligand is a versatile building block in coordination chemistry.

Purpose of the Study:

• Synthesize and characterize novel coordination polymers with interpenetrating networks.
• Investigate the structural, electronic, and magnetic properties of iron and zinc complexes.
• Explore the redox activity of the fluoranilate ligand in these materials.

Main Methods:

• Single-crystal X-ray diffraction for structural determination.
• Mössbauer spectroscopy to ascertain iron oxidation states.
• Magnetic susceptibility, electrochemical, and spectro-electrochemical studies.
• Conductivity measurements.

Main Results:

• Successful synthesis and structural characterization of (NBu4)2[M2(fan)3] (M = Fe, Zn) featuring interpenetrating (10,3)-a networks.
• Iron centers in the Fe complex are near +3 oxidation state, while zinc centers are +2.
• The fluoranilate ligand exhibits mixed valency in the Fe complex, with an average oxidation state between -2 and -3.
• The Fe complex demonstrates semiconductor behavior attributed to mixed-valent fluoranilate ligands.
• The fluoranilate ligand is redox-active in both complexes, with a reduced form of the Fe complex generated.

Conclusions:

• The synthesized coordination polymers exhibit distinct properties based on the metal center, particularly concerning ligand oxidation states and electronic behavior.
• The iron-based coordination polymer is a semiconductor, highlighting the role of mixed-valent fluoranilate ligands.
• These findings contribute to the understanding of structure-property relationships in interpenetrating coordination networks.