Mimicking Class Ib Mn2 -Ribonucleotide Reductase: A MnII2 Complex and Its Reaction with Superoxide
Item Type:Journal Article
Citation:Magherusan, A M, Zhou, A, Farquhar, E R, Garcia-Melchor, M, Twamley, B, Que, L. Jr., McDonald, A A. Mimicking Class Ib Mn2 -Ribonucleotide Reductase: A MnII2 Complex and Its Reaction with Superoxide, Angewandte Chemie - International Edition, 2018, 130
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A fascinating discovery in the chemistry of ribonucleotide reductases (RNRs) has been the identification of a dimanganese (Mn2 ) active site in class I b RNRs that requires superoxide anion (O2.- ), rather than dioxygen (O2 ), to access a high-valent Mn2 oxidant. Complex 1 ([Mn2 (O2 CCH3 )(N-Et-HPTB)](ClO4 )2 , N-Et-HPTB=N,N,N',N'-tetrakis(2-(1-ethylbenzimidazolyl))-2-hydroxy-1,3-diaminopropane) was synthesised in high yield (90 %). 1 was reacted with O2.- at -40 °C resulting in the formation of a metastable species (2). 2 displayed electronic absorption features (λmax =460, 610 nm) typical of a Mn-peroxide species and a 29-line EPR signal typical of a MnII MnIII entity. Mn K-edge X-ray absorption near-edge spectroscopy (XANES) suggested a formal oxidation state change of MnII2 in 1 to MnII MnIII for 2. Electrospray ionisation mass spectrometry (ESI-MS) suggested 2 to be a MnII MnIII -peroxide complex. 2 was capable of oxidizing ferrocene and weak O-H bonds upon activation with proton donors. Our findings provide support for the postulated mechanism of O2.- activation at class I b Mn2 RNRs.
Author: Magherusan, Adriana M.; Zhou, Ang; Farquhar, Erik R.; Garcia-Melchor, Max; Twamley, Brendan; Que, Lawrence Jr.; McDonald, Aidan A.
Type of material:Journal Article
Series/Report no:Angewandte Chemie - International Edition;
Availability:Full text available
Keywords:Dioxygen/superoxide activation, Oxidation reactions, Ribonucleotide reductases, Bioinorganic chemistry, Dimanganese complexes