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Iron (II/III) Halide Complexes Promote the Interconversion of Nitric Oxide and S-nitrosothiols through Reversible Fe-S Interaction

submitted on 12.02.2021, 11:54 and posted on 15.02.2021, 04:51 by Anna Poptic, Shiyu Zhang
Heme and non-heme iron in biology mediate the storage/release of NO from S-nitrosothiols as a means to control the biological concentration of NO. Despite their importance in many physiological processes, the mechanisms of N-S bond formation/cleavage at Fe centers have been controversial. Herein, we report the interconversion of NO and S-nitrosothiols mediated by FeII/FeIII chloride complexes. The reaction of two equivalents of S-nitrosothiol (Ph3CSNO) with [Cl6FeII2]2- results in facile release of NO and formation of iron(III) halothiolate. Detailed spectroscopic studies, including in situ UV-vis, IR, and Mössbauer spectroscopy, support the interaction of the S−atom with the FeII center. This is in contrast to the proposed mechanism of NO release from the well-studied “red product” k1-N bound S-nitrosothiol FeII complex, [(CN)5Fe(k1-N-RSNO)]3-. Additionally, FeIII chloride can mediate NO storage through the formation of S-nitrosothiols. Treatment of iron(III) halothiolate with two equivalents of NO regenerates Ph3CSNO with the FeII source trapped as the S = 3/2 {FeNO}7 species [Cl3FeNO]-, which is inert towards further coordination and activation of S-nitrosothiols. Our work demonstrates how labile iron can mediate the interconversion of NO/thiolate and S-nitrosothiol, which has important implications for how Nature manages the biological concentration of free NO.


National Science Foundation CHE-1904560


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Ohio State University


United States

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no conflict of interest