Stereoelectronic Insight Into Heme Carbene Catalysis: Bridging Enzymatic and Synthetic Systems

Area of Science:

• Biochemistry
• Organometallic Chemistry
• Spectroscopy

Background:

• Iron porphyrin carbenes (IPCs) are key intermediates in enzymatic carbene transfer reactions.
• IPCs exhibit diverse bonding modes and electronic configurations influencing their catalytic roles.

Purpose of the Study:

• To systematically compare three IPC isomers: terminal carbenes, bridged carbenes, and N-alkyl derivatives.
• To correlate structural and electronic properties with catalytic functions in both enzymatic and synthetic systems.

Main Methods:

• X-ray crystal structure analysis to determine protein-induced structural adaptations.
• Mössbauer and electron paramagnetic resonance (EPR) spectroscopy for ground state assignments and electronic configuration analysis.
• Comparison of spectroscopic data with synthetic analogues.

Main Results:

• Identified distinct structural distortions and electronic configurations for each IPC isomer.
• Mössbauer studies revealed differences in Fe-C bond distances and π-acceptor capabilities among isomers.
• EPR spectroscopy showed large tetragonalities for bridged carbenes, indicating specific electronic environments.

Conclusions:

• Established critical links between synthetic porphyrin chemistry and enzymatic carbene transfer mechanisms.
• Demonstrated the role of engineered proteins in stabilizing diverse IPC intermediates.
• Advanced the mechanistic understanding of enzymatic carbene transfer reactions through isomer-specific analysis.