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Mimicking Class I b Mn 2 ‐Ribonucleotide Reductase: A Mn II 2 Complex and Its Reaction with Superoxide
A fascinating discovery in the chemistry of ribonucleotide reductases (RNRs) has been the identification of a dimanganese (Mn 2 ) active site in class I b RNRs that requires superoxide anion (O 2 .− ), rather than dioxygen (O 2 ), to access a high‐valent Mn 2 oxidant. Complex 1 ([Mn 2 (O 2 CCH 3 )(N...
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Published in: | Angewandte Chemie 2018-01, Vol.130 (4), p.930-934 |
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Main Authors: | , , , , , , |
Format: | Article |
Language: | English |
Citations: | Items that this one cites Items that cite this one |
Online Access: | Get full text |
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Summary: | A fascinating discovery in the chemistry of ribonucleotide reductases (RNRs) has been the identification of a dimanganese (Mn
2
) active site in class I b RNRs that requires superoxide anion (O
2
.−
), rather than dioxygen (O
2
), to access a high‐valent Mn
2
oxidant. Complex
1
([Mn
2
(O
2
CCH
3
)(N‐Et‐HPTB)](ClO
4
)
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 O
2
.−
at −40 °C resulting in the formation of a metastable species (
2
).
2
displayed electronic absorption features (
λ
max
=460, 610 nm) typical of a Mn‐peroxide species and a 29‐line EPR signal typical of a Mn
II
Mn
III
entity. Mn K‐edge X‐ray absorption near‐edge spectroscopy (XANES) suggested a formal oxidation state change of Mn
II
2
in
1
to Mn
II
Mn
III
for
2
. Electrospray ionisation mass spectrometry (ESI‐MS) suggested
2
to be a Mn
II
Mn
III
‐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 O
2
.−
activation at class I b Mn
2
RNRs. |
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ISSN: | 0044-8249 1521-3757 |
DOI: | 10.1002/ange.201709806 |