A bridged di-iron porphyrin hyponitrite complex as a model for biological N2O production from hyponitrite

• A rare heme model-hyponitrite complex has been prepared and characterized.
• Infrared spectroscopy indicates a bridging mode of the hyponitrite ligand to both Fe centers in this bimetallic complex.
• The di-Fe hyponitrite compound converts to N2O at room temperature without the need for added protons
• A new bridged di-iron porphyrin sulfato compound has been characterized by X-ray crystallography.

Heme-hyponitrites are intermediates that form at the bimetallic active sites of bacterial nitric oxide reductases. To probe a possible effect of the Fe–Fe distance on hyponitrite stability, we prepared a bridged bis-porphyrin Fe-hyponitrite compound, namely [(OEP-CH2)Fe]2(μ2,η1,η1-ONNO). Its υNO of 992 cm−1 (υ15NO of 976 cm−1) is close to the υNO of 983 cm−1 reported previously by us for the crystallographically characterized [(OEP)Fe]2(μ2,η1,η1-ONNO) compound. The bridged bis-porphyrin Fe-hyponitrite complex is unstable with respect to N2O production, supporting the role of the bis-Fe porphyrin system in hyponitrite conversion to N2O. The preparation and crystallographic determination of the bridging sulfato derivative is also reported.