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1.
Khaled Cheaib M. Qadri E. Mubarak Katell Snchal‐David Christian Herrero Rgis Guillot Martin Clmancey Jean‐Marc Latour Sam P. deVisser Jean‐Pierre Mahy Frdric Banse Frdric Avenier 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(3):864-868
We demonstrate that the devised incorporation of an alkylamine group into the second coordination sphere of an FeII complex allows to switch its reactivity with H2O2 from the usual formation of FeIII species towards the selective generation of an FeIV‐oxo intermediate. The FeIV‐oxo species was characterized by UV/Vis absorption and Mössbauer spectroscopy. Variable‐temperature kinetic analyses point towards a mechanism in which the heterolytic cleavage of the O?O bond is triggered by a proton transfer from the proximal to the distal oxygen atom in the FeII‐H2O2 complex with the assistance of the pendant amine. DFT studies reveal that this heterolytic cleavage is actually initiated by an homolytic O?O cleavage immediately followed by a proton‐coupled electron transfer (PCET) that leads to the formation of the FeIV‐oxo and release of water through a concerted mechanism. 相似文献
2.
Olsson E Martinez A Teigen K Jensen VR 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(13):3746-3758
The first part of the catalytic cycle of the pterin‐dependent, dioxygen‐using nonheme‐iron aromatic amino acid hydroxylases, leading to the FeIV?O hydroxylating intermediate, has been investigated by means of density functional theory. The starting structure in the present investigation is the water‐free Fe? O2 complex cluster model that represents the catalytically competent form of the enzymes. A model for this structure was obtained in a previous study of water‐ligand dissociation from the hexacoordinate model complex of the X‐ray crystal structure of the catalytic domain of phenylalanine hydroxylase in complex with the cofactor (6R)‐L ‐erythro‐5,6,7,8‐tetrahydrobiopterin (BH4) (PAH‐FeII‐BH4). The O? O bond rupture and two‐electron oxidation of the cofactor are found to take place via a Fe‐O‐O‐BH4 bridge structure that is formed in consecutive radical reactions involving a superoxide ion, O2?. The overall effective free‐energy barrier to formation of the FeIV?O species is calculated to be 13.9 kcal mol?1, less than 2 kcal mol?1 lower than that derived from experiment. The rate‐limiting step is associated with a one‐electron transfer from the cofactor to dioxygen, whereas the spin inversion needed to arrive at the quintet state in which the O? O bond cleavage is finalized, essentially proceeds without activation. 相似文献
3.
Sayanti Chatterjee Tapan Kanti Paine 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2015,127(32):9470-9474
Many iron‐containing enzymes involve metal–oxygen oxidants to carry out O2‐dependent transformation reactions. However, the selective oxidation of C H and CC bonds by biomimetic complexes using O2 remains a major challenge in bioinspired catalysis. The reactivity of iron–oxygen oxidants generated from an FeII–benzilate complex of a facial N3 ligand were thus investigated. The complex reacted with O2 to form a nucleophilic oxidant, whereas an electrophilic oxidant, intercepted by external substrates, was generated in the presence of a Lewis acid. Based on the mechanistic studies, a nucleophilic FeII–hydroperoxo species is proposed to form from the benzilate complex, which undergoes heterolytic O O bond cleavage in the presence of a Lewis acid to generate an FeIV–oxo–hydroxo oxidant. The electrophilic iron–oxygen oxidant selectively oxidizes sulfides to sulfoxides, alkenes to cis‐diols, and it hydroxylates the C H bonds of alkanes, including that of cyclohexane. 相似文献
4.
Olefin cis‐Dihydroxylation and Aliphatic CH Bond Oxygenation by a Dioxygen‐Derived Electrophilic Iron–Oxygen Oxidant
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Sayanti Chatterjee Dr. Tapan Kanti Paine 《Angewandte Chemie (International ed. in English)》2015,54(32):9338-9342
Many iron‐containing enzymes involve metal–oxygen oxidants to carry out O2‐dependent transformation reactions. However, the selective oxidation of C? H and C?C bonds by biomimetic complexes using O2 remains a major challenge in bioinspired catalysis. The reactivity of iron–oxygen oxidants generated from an FeII–benzilate complex of a facial N3 ligand were thus investigated. The complex reacted with O2 to form a nucleophilic oxidant, whereas an electrophilic oxidant, intercepted by external substrates, was generated in the presence of a Lewis acid. Based on the mechanistic studies, a nucleophilic FeII–hydroperoxo species is proposed to form from the benzilate complex, which undergoes heterolytic O? O bond cleavage in the presence of a Lewis acid to generate an FeIV–oxo–hydroxo oxidant. The electrophilic iron–oxygen oxidant selectively oxidizes sulfides to sulfoxides, alkenes to cis‐diols, and it hydroxylates the C? H bonds of alkanes, including that of cyclohexane. 相似文献
5.
An Artificial Enzyme Made by Covalent Grafting of an FeII Complex into β‐Lactoglobulin: Molecular Chemistry,Oxidation Catalysis,and Reaction‐Intermediate Monitoring in a Protein
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Charlotte Buron Dr. Katell Sénéchal‐David Dr. Rémy Ricoux Jean‐Pierre Le Caër Vincent Guérineau Dr. Philippe Méjanelle Dr. Régis Guillot Dr. Christian Herrero Prof. Jean‐Pierre Mahy Prof. Frédéric Banse 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(34):12188-12193
An artificial metalloenzyme based on the covalent grafting of a nonheme FeII polyazadentate complex into bovine β‐lactoglobulin has been prepared and characterized by using various spectroscopic techniques. Attachment of the FeII catalyst to the protein scaffold is shown to occur specifically at Cys121. In addition, spectrophotometric titration with cyanide ions based on the spin‐state conversion of the initial high spin (S=2) FeII complex into a low spin (S=0) one allows qualitative and quantitative characterization of the metal center’s first coordination sphere. This biohybrid catalyst activates hydrogen peroxide to oxidize thioanisole into phenylmethylsulfoxide as the sole product with an enantiomeric excess of up to 20 %. Investigation of the reaction between the biohybrid system and H2O2 reveals the generation of a high spin (S=5/2) FeIII(η2‐O2) intermediate, which is proposed to be responsible for the catalytic sulfoxidation of the substrate. 相似文献
6.
Azwana R. Sadique William W. Brennessel Patrick L. Holland 《Acta Crystallographica. Section C, Structural Chemistry》2009,65(5):m174-m176
Reduction of carbon dioxide by a diiron(I) complex gives μ‐carbonato‐κ3O:O′,O′′‐bis{[2,2,6,6‐tetramethyl‐3,5‐bis(2,4,6‐triisopropylphenyl)heptane‐2,5‐diiminate(1−)‐κ2N,N′]iron(II)} toluene disolvate, [Fe2(C41H65N)2(CO3)]·2C7H8, a diiron(II) species with a bridging carbonate ligand. The asymmetric unit contains one diiron complex and two cocrystallized toluene solvent molecules that are distributed over three sites, one with atoms in general positions and two in crystallographic sites. Both FeII atoms are η2‐coordinated to diketiminate ligands, but η1‐ and η2‐coordinated to the bridging carbonate ligand. Thus, one FeII center is three‐coordinate and the other is four‐coordinate. The bridging carbonate ligand is nearly perpendicular to the iron–diketiminate plane of the four‐coordinate FeII center and parallel to the plane of the three‐coordinate FeII center. 相似文献
7.
Dr. Prokopis C. Andrikopoulos Dr. Zdenek Sobalik Dr. Jana Novakova Dr. Petr Sazama Dr. Stepan Sklenak 《Chemphyschem》2013,14(3):520-531
The role of framework oxygen atoms in N2O decomposition [N2O(g)→N2(g) and 1/2O2(g)] over Fe‐ferrierite is investigated employing a combined experimental (N218O decomposition in batch experiments followed by mass spectroscopy measurements) and theoretical (density functional theory calculations) approach. The occurrence of the isotope exchange indicates that framework oxygen atoms are involved in the N2O decomposition catalyzed by Fe‐ferrierite. Our study, using an Fe‐ferrierite sample with iron exclusively present as FeII cations accommodated in the cationic sites, shows that the mobility of framework oxygen atoms in the temperature range: 553 to 593 K is limited to the four framework oxygen atoms of the two AlO4? tetrahedra forming cationic sites that accomodate FeII. They exchange with the Fe extra‐framework 18O atom originating from the decomposed N218O. We found, using DFT calculations, that O2 molecules facilitate the oxygen exchange. However, the corresponding calculated energy barrier of 87 kcal mol?1 is still very high and it is higher than the assumed experimental value based on the occurrence of the sluggish oxygen exchange at 553 K. 相似文献
8.
A 1:1 inclusion complex (FeIIPImCD) of 5,10,15,20‐tetrakis‐ (4‐sulfonatophenyl)porphinatoiron(II) (FeIIP) and an O‐methylated β‐cyclodextrin dimer with an imidazole linker (ImCD) was found to bind dioxygen in aqueous solution. The half‐saturation pressure of dioxygen (P1/2O2) is 1.7 torr at 25 °C, which is 10 times lower than that for a previous myoglobin functional model (hemoCD) with a pyridine linker. Meanwhile, the half‐life of oxygenated FeIIPImCD is 3 h, which is 10 times shorter than that of oxygenated hemoCD. The covering of the iron(II) center by a microscopic environment is essential for preventing autoxidation of oxygenated ferrous porphyrin, which is promoted by nucleophilic attack of H2O and/or nucleophiles such as inorganic anions. Due to structural requirements, covering of the FeII center of FeIIPImCD is insufficient compared with the case of hemoCD. As a result, water molecules can penetrate more easily the cleft of the O2–FeIIPImCD complex and act as an autoxidation inducer. This structure also causes poorer selectivity against carbon monoxide (M=1040). In contrast, the dioxygen affinity of FeIIPImCD is much higher than that of hemoCD because the imidazole moiety is a stronger electron donor than pyridine. 相似文献
9.
Photomagnetic Response in Highly Conductive Iron(II) Spin‐Crossover Complexes with TCNQ Radicals
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Hoa Phan Shermane M. Benjamin Eden Steven Prof. Michael Shatruk 《Angewandte Chemie (International ed. in English)》2015,54(3):823-827
Co‐crystallization of a cationic FeII complex with a partially charged TCNQ.δ? (7,7′,8,8′‐tetracyanoquinodimethane) radical anion has afforded molecular materials that behave as narrow band‐gap semiconductors, [Fe(tpma)(xbim)](X)(TCNQ)1.5?DMF (X=ClO4? or BF4?; tpma=tris(2‐pyridylmethyl)amine, xbim=1,1′‐(α,α′‐o‐xylyl)‐2,2′‐bisimidazole). Remarkably, these complexes also exhibit temperature‐and light‐driven spin crossover at the FeII center, and are thus the first structurally defined magnetically bistable semiconductors assembled with the TCNQ.δ? radical anion. Transport measurements reveal the conductivity of 0.2 S cm?1 at 300 K, with the low activation energy of 0.11 eV. 相似文献
10.
Three new iron(II)‐benzilate complexes [(N4Py)FeII(benzilate)]ClO4 ( 1 ), [(N4PyMe2)FeII(benzilate)]ClO4 ( 2 ) and [(N4PyMe4)FeII(benzilate)]ClO4 ( 3 ) of neutral pentadentate nitrogen donor ligands have been isolated and characterized to study their dioxygen reactivity. Single‐crystal X‐ray structures reveal a mononuclear six‐coordinate iron(II) center in each case, where benzilate binds to the iron center in monodentate mode via one carboxylate oxygen. Introduction of methyl groups in the 6‐positions of the pyridine rings makes the N4PyMe2 and N4PyMe4 ligand fields weaker compared to that of the parent N4Py ligand. All the complexes ( 1 – 3 ) react with dioxygen to decarboxylate the coordinated benzilate to benzophenone quantitatively. The decarboxylation is faster for the complex of the more sterically hindered ligand and follows the order 3 > 2 > 1 . The complexes display oxygen atom transfer reactivity to thioanisole and also exhibit hydrogen atom transfer reactions with substrates containing weak C?H bonds. Based on interception studies with external substrates, labelling experiments and Hammett analysis, a nucleophilic iron(II)‐hydroperoxo species is proposed to form upon two‐electron reductive activation of dioxygen by each iron(II)‐benzilate complex. The nucleophilic oxidants are converted to the corresponding electrophilic iron(IV)‐oxo oxidant upon treatment with a protic acid. The high‐spin iron(II)‐benzilate complex with the weakest ligand field results in the formation of a more reactive iron‐oxygen oxidant. 相似文献
11.
12.
Dr. Joel Torres‐Alacan Oliver Krahe Prof. Dr. Alexander C. Filippou Prof. Dr. Frank Neese Prof. Dr. Dirk Schwarzer Prof. Dr. Peter Vöhringer 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(10):3043-3055
The photochemistry of iron azido complexes is quite challenging and poorly understood. For example, the photochemical decomposition of [FeIIIN3(cyclam‐ac)]PF6 ([ 1 ]PF6), where cyclam‐ac represents the 1,4,8,11‐tetraazacyclotetradecane‐1‐acetate ligand, has been shown to be wavelength‐dependent, leading either to the rare high‐valent iron(V) nitrido complex [FeVN(cyclam‐ac)]PF6 ([ 3 ]PF6) after cleavage of the azide Nα? Nβ bond, or to a photoreduced FeII species after Fe? Nazide bond homolysis. The mechanistic details of this intriguing reactivity have never been studied in detail. Here, the photochemistry of 1 in acetonitrile solution at room temperature has been investigated using step‐scan and rapid‐scan time‐resolved Fourier transform infrared (FTIR) spectroscopy following a 266 nm, 10 ns pulsed laser excitation. Using carbon monoxide as a quencher for the primary iron‐containing photochemical product, it is shown that 266 nm excitation of 1 results exclusively in the cleavage of the Fe? Nazide bond, as was suspected from earlier steady‐state irradiation studies. In argon‐purged solutions of [ 1 ]PF6, the solvent‐stabilized complex cation [FeII(CH3CN)(cyclam‐ac)]+ ( 2 red ) together with the azide radical (N3.) is formed with a relative yield of 80 %, as evidenced by the appearance of their characteristic vibrational resonances. Strikingly, step‐scan experiments with a higher time resolution reveal the formation of azide anions (N3?) during the first 500 ns after photolysis, with a yield of 20 %. These azide ions can subsequently react thermally with 2 red to form [FeIIN3(cyclam‐ac)] ( 1 red ) as a secondary product of the photochemical decomposition of 1 . Molecular oxygen was further used to quench 1 red and 2 red to form what seems to be the elusive complex [Fe(O2)(cyclam‐ac)]+ ( 6 ). 相似文献
13.
High Sensitive Microsensor Based on Organic‐Inorganic Composite for Two‐Dimensional Mapping of H2O2 by SECM
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Danielle Diniz Justino Isabel Lourenço Torres Rita de Cássia Silva Luz Flavio Santos Damos 《Electroanalysis》2015,27(5):1202-1209
The present work describes the development of a selective, sensitive and stable sensing microsensor for scanning electrochemical microscopy (SECM) to measure H2O2 during electrochemical reduction of oxygen. The microsensor is based on graphene and Poly(3,4‐ethylenedioxythiophene) composite as support to iron (III) hexacyanoferrate (II) (PEDOT/graphene/FeIII4[FeII(CN)6]3 microsensor). The electrochemical properties of the PEDOT/graphene/FeIII4[FeII(CN)6]3 microsensor were investigated by cyclic voltammetry (CV) and scanning electrochemical microscopy (SECM). The PEDOT/graphene/FeIII4[FeII(CN)6]3 microsensor showed an excellent electrocatalytic activity toward hydrogen peroxide (H2O2) reduction with a diminution of the overpotential of about 500 mV in comparison to the process at a bare gold microelectrode. The microsensor presented excellent performance for two dimensional mapping of H2O2 by SECM in 0.1 mol L?1 phosphate buffer solution (pH 7.0). Under optimized conditions, a linear response range from 1 up to 1000 µmol L?1 was obtained with a sensitivity of 0.08 nA L µmol?1 and limit of detection of 0.5 µmol L?1. 相似文献
14.
Decay of Iron(V) Nitride Complexes By a NN Bond‐Coupling Reaction in Solution: A Combined Spectroscopic and Theoretical Analysis
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Oliver Krahe Dr. Eckhard Bill Prof. Dr. Frank Neese 《Angewandte Chemie (International ed. in English)》2014,53(33):8727-8731
Cryogenically trapped FeV nitride complexes with cyclam‐based ligands were found to decay by bimolecular reactions, forming exclusively FeII compounds. Characterization of educts and products by Mössbauer spectroscopy, mass spectrometry, and spectroscopy‐oriented DFT calculations showed that the reaction mechanism is reductive nitride coupling and release of dinitrogen (2 FeV?N→FeII‐N?N‐FeII→2 FeII+N2). The reaction pathways, representing an “inverse” of the Haber–Bosch reaction, were computationally explored in detail, also to judge the feasibility of yielding catalytically competent FeV(N). Implications for the photolytic cleavage of FeIII azides used to generate high‐valent Fe nitrides are discussed. 相似文献
15.
Azaj Ansari Dr. Prabha Jayapal Prof. Gopalan Rajaraman 《Angewandte Chemie (International ed. in English)》2015,54(2):564-568
Metal–superoxo species are ubiquitous in metalloenzymes and bioinorganic chemistry and are known for their high reactivity and their ability to activate inert C? H bonds. The comparative oxidative abilities of M–O2.? species (M=CrIII, MnIII, FeIII, and CuII) towards C? H bond activation reaction are presented. These superoxo species generated by oxygen activation are found to be aggressive oxidants compared to their high‐valent metal–oxo counterparts generated by O???O bond cleavage. Our calculations illustrate the superior oxidative abilities of FeIII– and MnIII–superoxo species compared to the others and suggest that the reactivity may be correlated to the magnetic exchange parameter. 相似文献
16.
Azaj Ansari Prabha Jayapal Gopalan Rajaraman 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2015,127(2):574-578
Metal–superoxo species are ubiquitous in metalloenzymes and bioinorganic chemistry and are known for their high reactivity and their ability to activate inert C H bonds. The comparative oxidative abilities of M–O2.− species (M=CrIII, MnIII, FeIII, and CuII) towards C H bond activation reaction are presented. These superoxo species generated by oxygen activation are found to be aggressive oxidants compared to their high‐valent metal–oxo counterparts generated by O⋅⋅⋅O bond cleavage. Our calculations illustrate the superior oxidative abilities of FeIII– and MnIII–superoxo species compared to the others and suggest that the reactivity may be correlated to the magnetic exchange parameter. 相似文献
17.
Juan‐Ramn Jimnez Jana Glatz Amina Benchohra Geoffrey Gontard Lise‐Marie Chamoreau Jean‐Franois Meunier Azzedine Bousseksou Rodrigue Lescouëzec 《Angewandte Chemie (International ed. in English)》2020,59(21):8089-8093
A mixed‐valence {MnII3MnIIIFeII2FeIII2} cyanide‐bridged molecular cube hosting a caesium cation, Cs?{Mn4Fe4}, was synthesized and structurally characterized by X‐ray diffraction. Cyclic‐voltammetry measurements show that its electronic state can be switched between five different redox states, which results in a remarkable electrochromic effect. Magnetic measurements on fresh samples point to the occurrence of a spin‐state change near room temperature, which could be ascribed to a metal‐to‐metal electron transfer converting the {FeII?CN?MnIII} pair into a {FeIII?CN?MnII} pair. This feature was only previously observed in the polymeric MnFe Prussian‐blue analogues (PBAs). Moreover, this novel switchable molecule proved to be soluble and stable in organic solvents, paving the way for its integration into advanced materials. 相似文献
18.
A Strategy to Promote the Electrocatalytic Activity of Spinels for Oxygen Reduction by Structure Reversal
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Dr. Guangping Wu Dr. Jun Wang Dr. Wei Ding Dr. Yao Nie Prof. Li Li Dr. Xueqiang Qi Dr. Siguo Chen Prof. Zidong Wei 《Angewandte Chemie (International ed. in English)》2016,55(4):1340-1344
The electrocatalytic performance of a spinel for the oxygen reduction reaction (ORR) can be significantly promoted by reversing its crystalline structure from the normal to the inverse. As the spinel structure reversed, the activation and cleavage of O?O bonds are accelerated owing to a dissimilarity effect of the distinct metal atoms co‐occupying octahedral sites. The CoIIFeIIICoIIIO4 spinel with the Fe and Co co‐occupying inverse structure exhibits an excellent ORR activity, which even exceeds that of the state‐of‐the‐art commercial Pt/C by 42 mV in alkaline medium. 相似文献
19.
Qian Zhang Xue Lv Yun Qiao Ling Zhang Da‐Liang Liu Wei Zhang Guang‐Xi Han Xi‐Ming Song 《Electroanalysis》2010,22(9):1000-1004
A polymer film based on polymeric ionic liquid, which was poly(1‐vinyl‐3‐butylimidazolium chloride) (poly(ViBuIm+Cl?)for short), was firstly used as matrix to immobilize hemoglobin (Hb). FTIR and UV‐vis spectra demonstrated that the native structure of Hb was well preserved after entrapped into the polymer film. The Hb immobilized in the poly(ViBuIm+Cl?) film showed a fast direct electron transfer for the Hb‐FeIII/FeII redox couple. Based on the direct electron transfer of the immobilized Hb, polyvinyl alcohol (PVA)/Hb/poly(ViBuIm+Cl?)/GC electrode displayed good sensitivity and wide linear range for the detection of H2O2. The linear range of the PVA/Hb/poly(ViBuIm+Cl?)/GC electrode to H2O2 is from 3.5 to 224 μM with a limit of detection of 1.17 μM. Such an avenue, which integrated polymeric ionic liquid and redox protein via a simple method, may provide a novel and efficient platform for the fabrication of biosensors, biofuel cells and other bioelectrochemical devices. 相似文献
20.
Jean-Noël Rebilly Christian Herrero Katell Snchal-David Rgis Guillot Tanya Inceoglu Hlne Maisonneuve Frdric Banse 《Chemical science》2021,12(47):15691
Redox metalloenzymes achieve very selective oxidation reactions under mild conditions using O2 or H2O2 as oxidants and release harmless side-products like water. Their oxidation selectivity is intrinsically linked to the control of the oxidizing species generated during the catalytic cycle. To do so, a second coordination sphere is used in order to create a pull effect during the activation of O2 or H2O2, thus ensuring a heterolytic O–O bond cleavage. Herein, we report the synthesis and study of a new non-heme FeII complex bearing a pentaazadentate first coordination sphere and a pendant phenol group. Its reaction with H2O2 generates the classical FeIIIOOH species at high H2O2 loading. But at low H2O2 concentrations, an FeIVO species is generated instead. The formation of the latter is directly related to the presence of the 2nd sphere phenol group. Kinetic, variable temperature and labelling studies support the involvement of the attached phenol as a second coordination sphere moiety (weak acid) during H2O2 activation. Our results suggest a direct FeII → FeIVO conversion directed by the 2nd sphere phenol via the protonation of the distal O atom of the FeII/H2O2 adduct leading to a heterolytic O–O bond cleavage.A new FeII complex with a phenol group attached as a second coordination sphere moiety activates H2O2 to yield FeIVO following a mechanism reminiscent of peroxidase enzymes. 相似文献