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1.
Mimicking Class I b Mn2‐Ribonucleotide Reductase: A MnII2 Complex and Its Reaction with Superoxide
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Adriana M. Magherusan Ang Zhou Erik R. Farquhar Max García‐Melchor Brendan Twamley Lawrence Que Jr. Aidan R. McDonald 《Angewandte Chemie (International ed. in English)》2018,57(4):918-922
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(O2CCH3)(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 MnIIMnIII entity. Mn K‐edge X‐ray absorption near‐edge spectroscopy (XANES) suggested a formal oxidation state change of MnII2 in 1 to MnIIMnIII for 2 . Electrospray ionisation mass spectrometry (ESI‐MS) suggested 2 to be a MnIIMnIII‐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. 相似文献
2.
Adriana M. Magherusan Subhasree Kal Daniel N. Nelis Lorna M. Doyle Erik R. Farquhar Lawrence Que Aidan R. McDonald 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(17):5774-5778
Ribonucleotide reductases (RNRs) are essential enzymes required for DNA synthesis. In class Ib Mn2 RNRs superoxide (O2.?) was postulated to react with the MnII2 core to yield a MnIIMnIII‐peroxide moiety. The reactivity of complex 1 ([MnII2(O2CCH3)2(BPMP)](ClO4), where HBPMP=2,6‐bis{[(bis(2‐pyridylmethyl)amino]methyl}‐4‐methylphenol) towards O2.? was investigated at ?90 °C, generating a metastable species, 2 . The electronic absorption spectrum of 2 displayed features (λmax=440, 590 nm) characteristic of a MnIIMnIII‐peroxide species, representing just the second example of such. Electron paramagnetic resonance and X‐ray absorption spectroscopies, and mass spectrometry supported the formulation of 2 as a MnIIMnIII‐peroxide complex. Unlike all other previously reported Mn2‐peroxides, which were unreactive, 2 proved to be a capable oxidant in aldehyde deformylation. Our studies provide insight into the mechanism of O2‐activation in Class Ib Mn2 RNRs, and the highly reactive intermediates in their catalytic cycle. 相似文献
3.
Andreas Geisselmann Peter Klüfers Bernd Pilawa 《Angewandte Chemie (International ed. in English)》1998,37(8):1119-1121
Just a “reducing” sugar —namely, D -mannose—is a starting material in the synthesis of a mixed-valence complex of manganese in the oxidation states +III and +IV . Ba2[MnIIIMnIV(β-D -ManfH−5)2]Cl⋅14 H2O (Manf=mannofuranose; the structure of the anion is shown on the right) is prepared in aqueous solution by oxidation of an analogous Mn2III complex with oxygen. In neutral solutions the MnIIIMnIV binuclear complex is formed by disproportionation of the Mn2III precursor. 相似文献
4.
The reaction of (diaqua)(N,N′‐ethylene‐bis(salicylidiniminato)manganese(III) with aqueous sulphite buffer results in the formation of the corresponding mono sulphito complex, [Mn(Salen)(SO3)]− (S‐bonded isomer) via three distinct paths: (i) Mn(Salen)(OH2)2+ + HSO3− → (k1); (ii) Mn(Salen)(OH2)2+ + SO32− → (k2); (III) Mn(Salen)(OH2)(OH) + SO32− → (k3) in the stopped flow time scale. The fact that the mono sulphito complex does not undergo further anation with SO32−/HSO3− may be attributed to the strong trans‐activating influence of the S‐bonded sulphite. The values of the rate constants (10−2ki/dm2 mol−1 s−1 at 25°C, I = 0.3 mol dm−3), ΔHi#/kJ mol−1 and ΔSi#/J K−1 mol−1 respectively are: 2.97 ± 0.27, 42.4 ± 0.2, −55.3 ± 0.6 (i = 1); 11.0 ± 0.8, 33 ± 3, −75 ± 10 (i = 2); 20.6 ± 1.9, 32.4 ± 0.2, −72.9 ± 0.6 (i = 3). The trend in reactivity (k2 > k1), a small labilizing effect of the coordinated hydroxo group (k3/k2 < 2), and substantially low values of ΔS# suggest that the mechanism of aqua ligand substitution of the diaqua, and aqua‐hydroxo complexes is most likely associative interchange (Ia). No evidence for the formation of the O‐bonded sulphito complex and the ligand isomerization in the sulphito complex, (MnIII‐OSO2 → MnIII‐SO3), ensures the selectivity of the MnIII centre toward the S‐end of the SIV species. The monosulphito complex further undergoes slow redox reaction in the presence of excess sulphite to produce MnII, S2O62− and SO42−. The formation of dithionate is a consequence of the fast dimerization of the SO3−. generated in the rate determining step and also SO42− formation is attributed to the fast scavenging of the SO3−. by the MnIII species via a redox path. The internal reduction of the MnIII centre in the monosulphito complex is insignificant. The redox reaction of the monosulphitomanganese(III) complex operates via two major paths, one involving HSO3− and the other SO32−. The electron transfer is believed to be outersphere type. The substantially negative values of activation entropies (ΔS# = −(1.3 ± 0.2) × 102 and −(1.6 ± 0.2) × 102 J K−1 mol−1 for the paths involving HSO3− and SO32− respectively) reflect a considerable degree of ordering of the reactants in the act of electron transfer. © 1999 John Wiley & Sons, Inc. Int J Chem Kinet 31: 627–635, 1999 相似文献
5.
Song YJ Lee SH Park HM Kim SH Goo HG Eom GH Lee JH Lah MS Kim Y Kim SJ Lee JE Lee HI Kim C 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(26):7336-7344
Two new mononuclear nonheme manganese(III) complexes of tetradentate ligands containing two deprotonated amide moieties, [Mn(bpc)Cl(H2O)] ( 1 ) and [Mn(Me2bpb)Cl(H2O)] ? CH3OH ( 2 ), were prepared and characterized. Complex 2 has also been characterized by X‐ray crystallography. Magnetic measurements revealed that the complexes are high spin (S=5/2) MnIII species with typical magnetic moments of 4.76 and 4.95 μB, respectively. These nonheme MnIII complexes efficiently catalyzed olefin epoxidation and alcohol oxidation upon treatment with MCPBA under mild experimental conditions. Olefin epoxidation by these catalysts is proposed to involve the multiple active oxidants MnV?O, MnIV?O, and MnIII? OO(O)CR. Evidence for this approach was derived from reactivity and Hammett studies, KIE (kH/kD) values, H218O‐exchange experiments, and the use of peroxyphenylacetic acid as a mechanistic probe. In addition, it has been proposed that the participation of MnV?O, MnIV?O, and MnIII? OOR could be controlled by changing the substrate concentration, and that partitioning between heterolysis and homolysis of the O? O bond of a Mn‐acylperoxo intermediate (Mn? OOC(O)R) might be significantly affected by the nature of solvent, and that the O? O bond of the Mn? OOC(O)R might proceed predominantly by heterolytic cleavage in protic solvent. Therefore, a discrete MnV?O intermediate appeared to be the dominant reactive species in protic solvents. Furthermore, we have observed close similarities between these nonheme MnIII complex systems and Mn(saloph) catalysts previously reported, suggesting that this simultaneous operation of the three active oxidants might prevail in all the manganese‐catalyzed olefin epoxidations, including Mn(salen), Mn(nonheme), and even Mn(porphyrin) complexes. This mechanism provides the greatest congruity with related oxidation reactions by using certain Mn complexes as catalysts. 相似文献
6.
Valeriu Mereacre Ayuk M. Ako Muhammad Nadeem Akhtar Anja Lindemann Christopher E. Anson Annie K. Powell 《Helvetica chimica acta》2009,92(11):2507-2524
Reactions of CeIII(NO3)3?6 H2O or (NH4)2[CeIV(NO3)6] with Mn‐containing starting materials result in seven novel polynuclear Ce or Ce/Mn complexes with pivalato (tBuCO ) and, in most cases, auxiliary N,O‐ or N,O,O‐donor ligands. With nuclearities ranging from 6–14, the compounds present aesthetically pleasing structures. Complexes [CeIV6(μ3‐O)4(μ3‐OH)4(μ‐O2CtBu)12] ( 1 ), [CeIV6MnIII4(μ4‐O)4(μ3‐O)4(O2CtBu)12(ea)4(OAc)4]?4 H2O?4 MeCN (ea?=2‐aminoethanolato; 2 ), [CeIV6MnIII8(μ4‐O)4(μ3‐O)8(pye)4(O2CtBu)18]2[CeIV6(μ3‐O)4(μ3‐OH)4(O2CtBu)10(NO3)4] [CeIII(NO3)5(H2O)]?21 MeCN (pye?=pyridine‐2‐ethanolato; 3 ), and [CeIV6CeIII2MnIII2(μ4‐O)4(μ3‐O)4(tbdea)2(O2CtBu)12(NO3)2(OAc)2]?4 CH2Cl2 (tbdea2?=2,2′‐(tert‐butylimino]bis[ethanolato]; 4 ) all contain structures based on an octahedral {CeIV6(μ3‐O)8} core, in which many of the O‐atoms are either protonated to give (μ3‐OH)? hydroxo ligands or coordinate to further metal centers (MnIII or CeIII) to give interstitial (μ4‐O)2? oxo bridges. The decanuclear complex [CeIV8CeIIIMnIII(μ4‐O)3(μ3‐O)3(μ3‐OH)2(μ‐OH)(bdea)4(O2CtBu)9.5(NO3)3.5(OAc)2]?1.5 MeCN (bdea2?=2,2′‐(butylimino]bis[ethanolato]; 5 ) contains a rather compact CeIV7 core with the CeIII and MnIII centers well‐separated from each other on the periphery. The aggregate in [CeIV4MnIV2(μ3‐O)4(bdea)2(O2CtBu)10(NO3)2]?4 MeCN ( 6 ) is based on a quasi‐planar {MnIV2CeIV4(μ3‐O)4} core made up of four edge‐sharing {MnIVCeIV2(μ3‐O)} or {CeIV3(μ3‐O)} triangles. The structure of [CeIV3MnIV4MnIII(μ4‐O)2(μ3‐O)7(O2CtBu)12(NO3)(furan)]?6 H2O ( 7 ?6 H2O) can be considered as {MnIV2CeIV2O4} and distorted {MnIV2MnIIICeIVO4} cubane units linked through a central (μ4‐O) bridge. The Ce6Mn8 equals the highest nuclearity yet reported for a heterometallic Ce/Mn aggregate. In contrast to most of the previously reported heterometallic Ce/Mn systems, which contain only CeIV and either MnIV or MnIII, some of the aggregates presented here show mixed valency, either MnIV/MnIII (see 7 ) or CeIV/CeIII (see 4 and 5 ). Interestingly, some of the compounds, including the heterovalent CeIV/CeIII 4 , could be obtained from either CeIII(NO3)3?6 H2O or (NH4)2[CeIV(NO3)6] as starting material. 相似文献
7.
Li‐Fang Zhang Zhong‐Hai Ni Zhi‐Min Zong Xian‐Yong Wei Chun‐Hua Ge Hui‐Zhong Kou 《Acta Crystallographica. Section C, Structural Chemistry》2005,61(12):m542-m544
In the title one‐dimensional complex, {[MnIII(C9H10NO2)2]Cl}n, the Schiff base ligand 2‐[(2‐hydroxyethyl)iminomethyl]phenolate (Hsae−) functions as both a bridging and a chelating ligand. The MnIII ion is six‐coordinated by two N and four O atoms from four different Hsae− ligands, yielding a distorted MnO4N2 octahedral environment. Each [MnIII(Hsae)2]+ cationic unit has the Mn atom on an inversion centre and each [MnIII(Hsae)2]+ cation lies about another inversion centre. The chain‐like complex is further extended into a three‐dimensional network structure through Cl⋯H—O hydrogen bonds and C—H⋯π contacts involving the Hsae− rings. 相似文献
8.
Dr. Ioannis Liratzis Dr. Stephan Walleck Dr. Jan Oldengott Anja Stammler Dr. Hartmut Bögge Dr. Eckhard Bill Prof. Dr. Thorsten Glaser 《欧洲无机化学杂志》2023,26(5):e202200650
The ligand H6ioan has been used to synthesize the three dinuclear complexes [(ioan)MnIITiIV], [(ioan)FeIITiIV], and [(ioan)FeIIITiIV]+. The face-sharing bridging mode of the three phenolates provides short M-TiIV distances of ≈3.0 Å. Mössbauer spectra of [(ioan)FeIIITiIV]+ show a magnetically split six-line spectrum at 3 K in zero magnetic field demonstrating a slow magnetic relaxation. Magnetic measurements provide a zero-field splitting of |D|=5 cm−1 in [(ioan)FeIITiIV]. EPR spectroscopy demonstrates sizable zero-field splittings of the S=5/2 spin systems of [(ioan)MnIITiIV] (D=0.246 cm−1) and [(ioan)FeIIITiIV]+ (D<−1 cm−1) that can be related to enforced covalency of the M-Oph bonds. [(ioan)FeIIITiIV]+ exhibits a reversible reduction at −0.26 V vs. Fc+/Fc demonstrating the facile accessibility of FeIII and FeII. In contrast to an irreversible oxidation in [(ioan)NiIITiIV] at 0.78 V vs. Fc+/Fc, the reversible oxidation at 0.25 V vs. Fc+/Fc in [(ioan)MnIITiIV] indicates even the access of MnIII. These results indicate that pentanuclear complexes [(ioan)FeM1M2M1Fe(ioan)]n+ are meaningful targets to access electron delocalization in mixed-valence systems over five ions due to the facile accessibility of both FeII and FeIII in the terminal positions. This study provides important local spin-Hamiltonian and Mössbauer parameters that will be essential for the understanding of the potentially complicated electronic structure in the anticipated pentanuclear complexes. 相似文献
9.
Mechanistic Insight into the Nitric Oxide Dioxygenation Reaction of Nonheme Iron(III)–Superoxo and Manganese(IV)–Peroxo Complexes
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Dr. Seungwoo Hong Dr. Pankaj Kumar Dr. Kyung‐Bin Cho Dr. Yong‐Min Lee Prof. Dr. Kenneth D. Karlin Prof. Dr. Wonwoo Nam 《Angewandte Chemie (International ed. in English)》2016,55(40):12403-12407
Reactions of nonheme FeIII–superoxo and MnIV–peroxo complexes bearing a common tetraamido macrocyclic ligand (TAML), namely [(TAML)FeIII(O2)]2? and [(TAML)MnIV(O2)]2?, with nitric oxide (NO) afford the FeIII–NO3 complex [(TAML)FeIII(NO3)]2? and the MnV–oxo complex [(TAML)MnV(O)]? plus NO2?, respectively. Mechanistic studies, including density functional theory (DFT) calculations, reveal that MIII–peroxynitrite (M=Fe and Mn) species, generated in the reactions of [(TAML)FeIII(O2)]2? and [(TAML)MnIV(O2)]2? with NO, are converted into MIV(O) and .NO2 species through O?O bond homolysis of the peroxynitrite ligand. Then, a rebound of FeIV(O) with .NO2 affords [(TAML)FeIII(NO3)]2?, whereas electron transfer from MnIV(O) to .NO2 yields [(TAML)MnV(O)]? plus NO2?. 相似文献
10.
Synthesis of six hydroxo-bridged binuclear manganese(III) complexes of formulae [MnL-X-MnL](ClO4) [X = OH (1–6)] along with a mononuclear manganese(III) complex (7) [Mn(L)(L′)(MeOH)2] [HL′ = 2-(2-hydroxy-phen-yl)benzimidazole] and two carboxylate-bridged binuclear manganese(III) complexes (8) and (9) are described. The complexes have been characterized by the combination of i.r., u.v.-vis spectroscopy, magnetic moments and by their redox properties. The electronic spectra of all the complexes exhibit almost identical features consisting of two d–d bands at ca. 550 and 600 nm, one MLCT band at ca.400 nm, together with two π–π* intra-ligand transitions at ca. 250 nm and ca.300 nm. Room temperature magnetic data range from μ = 2.7–3.0 BM indicates some super-exchange between the binuclear metal centers via bridging hydroxo/carboxylato groups. The X-ray crystal structure of the binuclear complex (5) revealed that it has a symmetric MnIIIN2O2 core bridged by a hydroxyl group. The X-ray analysis of the mononuclear complex (7) showed that the manganese-center possesses a distorted octahedral geometry. Electrochemical properties of hydroxo-bridged manganese(III) complexes (1–6) show identical features consisting of an irreversible and a quasi-reversible reduction corresponding to the Mn2III → MnIIMnIII → MnIIMnII couples in the voltammogram. It was found that electron withdrawing substituents on the ligand result in easier reduction. Complex (7) displays an irreversible reduction at 0.08 V and a reversible oxidation at 0.45V assignable to the MnIII → MnII reduction and MnIII → MnIV oxidation, respectively. The carboxylate-bridged compound (8) exhibits two irreversible oxidations at 0.4 and 0.6 V, probably due to Mn2III → MnIIIMnIV → MnIVMnIV oxidations and shows a quasi-reversible reductive wave at −0.85 V, tentatively assigned to Mn2III → MnIIMnIII reduction. 相似文献
11.
Danick Reynard Dr. Sunny Maye Dr. Pekka Peljo Vimanshu Chanda Prof. Hubert H. Girault Dr. Solène Gentil 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(32):7250-7257
The MnIII/MnII redox couple with a standard potential of +1.51 V versus the standard hydrogen electrode (SHE) has attracted interest for the design of V/Mn redox flow batteries (RFBs). However, MnIII disproportionation leads to a loss of capacity, an increase in pressure drop, and electrode passivation caused by the formation of MnO2 particles during battery cycling. In this work, the influence of TiIV or/and VV on MnIII stability in acidic conditions is studied by formulating four different electrolytes in equimolar ratios (Mn, Mn/Ti, Mn/V, Mn/V/Ti). Voltammetry studies have revealed an ECi process for MnII oxidation responsible for the electrode passivation. SEM and XPS analysis demonstrate that the nature and morphology of the passivating oxides layer depend strongly on the electrolyte composition. Spectroelectrochemistry highlights the stabilization effect of TiIV and VV on MnIII. At a comparable pH, the amount of MnIII loss through disproportionation is decreased by a factor of 2.5 in the presence of TiIV or/and VV. Therefore, VV is an efficient substitute for TiIV to stabilize the MnIII electrolyte for RFB applications. 相似文献
12.
《Journal of Coordination Chemistry》2012,65(17):2893-2902
The complex [MnIV(napbh)2] (napbhH2 = N-(2-hydroxynaphthalen-1-yl)methylenebenzoylhydrazide) reacts with activated ruthenium(III) chloride in methanol in 1 : 1.2 molar ratio under reflux, giving heterobimetallic complexes, [MnIV(napbh)2RuIIICl3(H2O)] · [RuIII(napbhH)Cl2(H2O)] reacts with Mn(OAc)2·4H2O in methanol in 1 : 1.2 molar ratio under reflux to give [RuIII(napbhH)Cl2(H2O)MnII(OAc)2]. Replacement of aquo in these heterobimetallic complexes has been observed when the reactions are carried out in the presence of pyridine (py), 3-picoline (3-pic), or 4-picoline (4-pic). The molar conductances for these complexes in DMF indicates 1 : 1 electrolytes. Magnetic moment values suggest that these heterobimetallic complexes contain MnIV and RuIII or RuIII and MnII in the same structural unit. Electronic spectral studies suggest six coordinate metal ions. IR spectra reveal that the napbhH2 ligand coordinates in its enol form to MnIV and bridges to RuIII and in the keto form to RuIII and bridging to MnII. 相似文献
13.
The MnIV complex of 1,8-bis(2-hydroxybenzamido)-3,6-diazaoctane (MnIVL) with phenolate-amido-amine coordination is reduced by l-ascorbic acid and oxalic acid obeying overall 1:1 stoichiometry. The reactions are biphasic and MnIIIL− is the reactive intermediate. The product of oxidation of ascorbic acid (H2Asc) is dehydroascorbic acid and that of oxalic acid (H2OX) is CO2, while MnII is the end product from MnIV. Both MnIVL and MnIIIL− form outer sphere adducts with H2Asc and H2OX with high values of equilibrium constants of formation (Q>102 dm3 mol−1, I = 0.5 mol dm−3, 25.8 °C, 1.5% v/v MeOH+H2O). The adduct formation is diffusion controlled and is attributed to hydrogen bonding interactions between the reactants.
The rate constants for the electron transfer in (MnIV/IIIL, H2A), (MnIV/IIIL, HA−) (H2A = H2Asc, H2OX) and for (MnIVL, H2Asc)+H2Asc, (MnIIIL−, HAsc−)+HAsc− are reported. There was no evidence of direct coordination of the reductants to the MnIV/III center indicating an outer sphere (ET) mechanism. 相似文献
14.
Haoliang Zhao Xiaojuan Qu Minggao Qin Weijun Yang 《Journal of Solid State Electrochemistry》2016,20(10):2773-2780
A new composite electrode material with iron-manganic oxide coating (Fe-Mn/Mn2O3) was prepared, and its catalytic performance for oxidizing cyclohexanol was investigated in this work. The new electrode material, based on iron substrate covered with electrolytic manganese, was obtained by further coating the manganese surface with 50 % manganese nitrate solution and then conducting program thermal decomposition treatment. X-ray diffraction (XRD) was used to determine the surface crystal phase compositions, which were Mn and Mn2O3. The catalytic results showed an excellent electrocatalytic performance on the oxidation of cyclohexanol, and the main products were cyclohexanone and hexanedioic acid. According to our experiment results and the literature reports, the existence of mixed valent MnIII and MnIV played a key role in the electrocatalytic oxidation process. A probable process was proposed: the MnIV seized the hydrogen from cyclohexanol, the resulting cyclohexaneoxy radical was oxidized into cyclohexanone, and then the absorbed cyclohexanone was further oxidized into hexanedioic acid. 相似文献
15.
16.
David Martínez Majid Motevalli Michael Watkinson 《Acta Crystallographica. Section C, Structural Chemistry》2002,58(4):m258-m260
The title compound, aquachloro{2,2′‐[1,2‐ethanediylbis(nitrilomethylidyne)]diphenolato‐κ4O,N,N′,O′}manganese(III),[MnCl(C16H14N2O2)(H2O)], is a neutral manganese(III) complex with a pseudo‐octahedral metal centre. The equatorial plane comprises the four donor atoms of the tetradentate Schiff base ligand [Mn—O 1.886 (4) and 1.893 (4) Å, and Mn—N 1.978 (5) and 1.982 (5) Å], with a water molecule [Mn—O 2.383 (4) Å] and a Cl? ligand [Mn—Cl 2.4680 (16) Å] completing the coordination sphere. The distorted geometry is highlighted by the marked displacement of the MnIII ion out of the least‐squares plane of the four Schiff base donor atoms by 0.165 (2) Å. These monomeric MnIII centres are then linked into a polymeric array via hydrogen bonds between the coordinated water molecule and the phenolic O‐atom donors of an adjacent MnIII centre [O—H?O 2.789 (5) and 2.881 (5) Å]. 相似文献
17.
Two‐Color Valence‐to‐Core X‐ray Emission Spectroscopy Tracks Cofactor Protonation State in a Class I Ribonucleotide Reductase
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Ryan J. Martinie Dr. Elizabeth J. Blaesi Prof. Dr. J. Martin Bollinger Jr. Prof. Dr. Carsten Krebs Dr. Kenneth D. Finkelstein Dr. Christopher J. Pollock 《Angewandte Chemie (International ed. in English)》2018,57(39):12754-12758
Proton transfer reactions are of central importance to a wide variety of biochemical processes, though determining proton location and monitoring proton transfers in biological systems is often extremely challenging. Herein, we use two‐color valence‐to‐core X‐ray emission spectroscopy (VtC XES) to identify protonation events across three oxidation states of the O2‐activating, radical‐initiating manganese–iron heterodinuclear cofactor in a class I‐c ribonucleotide reductase. This is the first application of VtC XES to an enzyme intermediate and the first simultaneous measurement of two‐color VtC spectra. In contrast to more conventional methods of assessing protonation state, VtC XES is a more direct probe applicable to a wide range of metalloenzyme systems. These data, coupled to insight provided by DFT calculations, allow the inorganic cores of the MnIVFeIV and MnIVFeIII states of the enzyme to be assigned as MnIV(μ‐O)2FeIV and MnIV(μ‐O)(μ‐OH)FeIII, respectively. 相似文献
18.
Sun Hwa Lee Li Xu Dr. Byeong Kwon Park Yuri V. Mironov Dr. Soo Hyun Kim Young Ju Song Cheal Kim Prof. Dr. Youngmee Kim Dr. Sung‐Jin Kim Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(15):4678-4685
Two new tetranuclear chalcocyanide cluster complexes, [{Mn(saloph)H2O}4Re4Q4(CN)12]?4 CH3OH? 8 H2O (saloph=N,N′‐o‐phenylenebis(salicylidenaminato), Q=Se ( 1 ‐Se), Te ( 2 ‐Te)), have been synthesized by the diffusion of a methanolic solution of [PPh4]4[Re4Q4(CN)12] into a methanolic solution of [Mn(saloph)]+. The structure of 2 ‐Te has been determined by X‐ray crystallography. These rhenium cluster‐supported [MnIII(saloph)] complexes have been found to efficiently catalyze a wide range of olefin epoxidations under mild experimental conditions in the presence of meta‐chloroperbenzoic acid (mCPBA). Olefin epoxidation by these catalysts is proposed to involve the multiple active oxidants MnV?O, MnIV?O, and MnIII? OOC(O)R. Evidence in support of this interpretation has been derived from reactivity and Hammett studies, H218O‐exchange experiments, and the use of peroxyphenylacetic acid as a mechanistic probe. Moreover, it has been observed that the participation of MnV?O, MnIV?O, and MnIII? OOC(O)R can be controlled by changing the substrate concentration. This mechanism provides the greatest congruity with related oxidation reactions that employ certain Mn complexes as catalysts. 相似文献
19.
Hagen Kaemmerer Dr. Valeriu Mereacre Dr. Ayuk M. Ako Dr. Samir Mameri Dr. Christopher E. Anson Dr. Rodolphe Clérac Prof. Annie K. Powell 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(61):15096-15102
In an assisted self-assembly approach starting from the [Mn6O2(piv)10(4-Me-py)2(pivH)2] cluster a family of Mn−Ln compounds (Ln=Pr−Yb) was synthesised. The reaction of [Mn6O2(piv)10(4-Me-py)2(pivH)2] ( 1 ) with N-methyldiethanolamine (mdeaH2) and Ln(NO3)3 ⋅ 6H2O in MeCN generally yields two main structure types: for Ln=Tb−Yb a previously reported Mn5Ln4 motif is obtained, whereas for Ln=Pr−Eu a series of Mn7Ln3 clusters is obtained. Within this series the GdIII analogue represents a special case because it shows both structural types as well as a third Mn2Ln2 inverse butterfly motif. Variation in reaction conditions allows access to different structure types across the whole series. This prompts further studies into the reaction mechanism of this cluster assisted self-assembly approach. For the Mn7Ln3 analogues reported here variable-temperature magnetic susceptibility measurements suggest that antiferromagnetic interactions between the spin carriers are dominant. Compounds incorporating Ln=NdIII( 2 ), SmIII( 3 ) and GdIII ( 5 ) display SMM behaviour. The slow relaxation of the magnetisation for these compounds was confirmed by ac measurements above 1.8 K. 相似文献
20.
Swapan Kumar Chandra Partha Chakraborty Animesh Chakravorty 《Journal of Chemical Sciences》1992,104(3):351-360
The reaction of Mn(CH3COO)3 2H2O with the carboxyl-rich ligand pyridine-2,6-dicarboxylic acid (H2L) in methanol affords a high-spin (S = 2) hydratedbis-complex. Structure determination has revealed the solid to be [MnIII(H2 L)(L)] [MnIIIL2] 5H2 O: space group P−1;Z = 2;a = 7.527(3)?3,b= 14.260(4)?,c = 16.080(6)?,α = 91.08(3)°,β = 103.58(3)°,γ= 105.41(3)° andV= 1611.2(10)?3. Each ligand is planar and is bonded in the tridentate O2N fashion. The MnO4N2 coordination spheres show large distortions from octahedral symmetry. The lattice is stabilised by an extensive network of
O…O hydrogen-bonding involving water molecules and carboxyl functions. Upon dissolution in water, protic redistribution occurs
and the complex acts as the mono-basic acid Mn(HL)(L) (pK, 4.3 ±0.05). The deprotonated complex displays high metal reduction potentials: MnIVL2-MnIIIL
2
−
, 1.05V; MnIIIL
2
−
MnIIL
2
2−
-, 0.28V vs. SCE 相似文献