Fast nitroxyl trapping by ferric porphyrins

Area of Science:

• Inorganic Chemistry
• Bioinorganic Chemistry
• Reaction Kinetics

Background:

• Iron porphyrins are crucial in biological systems.
• Understanding their reactivity with nitrogen oxides is important.
• Nitroxyl (HNO) is a reactive nitrogen species with biological relevance.

Purpose of the Study:

• To develop a versatile method for synthesizing iron(II) porphyrin nitrosyl complexes.
• To investigate the reactivity of iron(III) porphyrins as nitroxyl traps.
• To provide a model system for studying nitroxyl interactions with hemeproteins.

Main Methods:

• Reaction of iron(III) porphyrins (e.g., [FeIII(TPP)]+, [FeIII(TPPS)]3-) with nitroxyl donors (sodium trioxodinitrate, toluensulfohydroxamic acid).
• Conducting reactions in both organic solvents and aqueous media.
• Kinetic analysis of the reaction, including determination of rate constants.

Main Results:

• High yields of iron(II) porphyrin nitrosyl complexes were achieved.
• Iron(III) porphyrins demonstrated efficiency as nitroxyl traps.
• The kinetic rate constant for [FeIII(TPPS)]3- with sodium trioxodinitrate was determined (kon ≈ 1.00 x 10^7 M⁻¹s⁻¹).

Conclusions:

• A facile and high-yield method for preparing ferrous nitrosyl porphyrins was established.
• Ferric porphyrins serve as effective nitroxyl scavengers.
• This reaction system offers a valuable tool for modeling nitroxyl reactivity in biological contexts.