Hydrogen-Bonding Effects in Five-Coordinate High-Spin Imidazole-Ligated Iron(II) Porphyrinates

Area of Science:

• Inorganic Chemistry
• Coordination Chemistry
• Materials Science

Background:

• High-spin iron(II) porphyrinates are important in various chemical and biological systems.
• Understanding ligand interactions, such as hydrogen bonding, is crucial for tuning their properties.
• Previous studies suggest hydrogen bonding effects in these systems are often subtle.

Purpose of the Study:

• To investigate the influence of hydrogen bonding on the N-H group of coordinated imidazole in high-spin iron(II) porphyrinates.
• To prepare and characterize new iron(II) porphyrinate complexes with hydrogen bond acceptors.
• To elucidate the structural and electronic consequences of hydrogen bond formation.

Main Methods:

• Synthesis and characterization of new iron(II) porphyrinate complexes.
• X-ray structure determination of the synthesized complexes.
• Temperature-dependent Mössbauer spectroscopy to probe electronic configurations.

Main Results:

• New complexes based on [Fe(TPP)(2-MeHIm)] were prepared and characterized, with hydrogen bond acceptors including ethanol, tetramethylene sulfoxide, and 2-methylimidazole.
• X-ray crystallography revealed that Fe-N bond lengths and iron atom displacement were marginally different compared to non-hydrogen-bonded analogs.
• Mössbauer spectroscopy indicated that the hydrogen-bonded complexes share the same electronic configuration as their non-hydrogen-bonded counterparts.

Conclusions:

• Hydrogen bonding to the imidazole N-H group in high-spin iron(II) porphyrinates has subtle effects.
• Structural and spectroscopic data suggest that hydrogen bonding does not significantly alter the electronic configuration of these iron(II) systems.
• The study reinforces the understanding that hydrogen bonding's impact on five-coordinate high-spin iron(II) complexes is nuanced and requires careful investigation.