Abstract
Reaction of [Fe2(N-Et-HPTB)(CH3COS)](BF4)2 (1) with (NO)(BF4) produces a nonheme mononitrosyl diiron(II) complex, [Fe2(N-Et-HPTB)(NO)(DMF)3](BF4)3 (2). Complex 2 is the first example of a [FeII{Fe(NO)}7] species and is also the first example of a mononitrosyl diiron(II) complex that mediates the reduction of NO to N2O. This work describes the selective synthesis, detailed characterization and NO reduction activity of 2 and thus provides new insights regarding the mechanism of flavodiiron nitric oxide reductases.
Highlights
Is a key component in the defense mechanism against various invading pathogens.[2−5] While up to micromolar concentration of nitric oxide (NO) can be produced in the activated macrophages,[6,7] many microbes such as Desulfovibrio gigas,[8] Moorella thermoacetica[9] and Thermotoga maritima[10] reduce NO ntoitrnicitrooxuidseorxeidduec(tNas2eOs ()FbNyOeRxpsr)e.1s1s−in1g3 the The enzymes flavodiiron active site of FNOR from D. gigas[8] consists of two nonheme iron centers
Is a key component in the defense mechanism against various invading pathogens.[2−5] While up to micromolar concentration of NO can be produced in the activated macrophages,[6,7] many microbes such as Desulfovibrio gigas,[8] Moorella thermoacetica[9] and Thermotoga maritima[10] reduce NO
Structural characterization of 2 revealed an unprecedented mononitrosyl diiron(II) unit where one iron center is coordinated by one NO and one DMF molecule, while the other iron center is coordinated by two DMF molecules
Summary
Similar redox events due to the reduction of {Fe(NO)}7 units were observed at −1.1, −1.12 and −1.14 V (vs Cp2Fe+/Cp2Fe) for the previously reported complexes, 4,22 523 and 6,24 respectively This reduction of the {Fe(NO)}7 center to an {Fe(NO)}8 unit followed by denitrosylation of 2 to form N2O in turn generates a new redox event. The reduction event at −0.68 V may be related with the reduction of the oxidized reaction product Such an assignment is comparable with a previous report by one of us (Lehnert) where the generation of a new feature at −0.56 V was assigned to the reaction product (oxo-bridged diferrous complex) after denitrosylation of 4,22 consistent with N2O formation upon electrochemical reduction of 4.22 The oxidation of the {Fe(NO)}8 unit in the reverse scan to regenerate.
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