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1.
Well‐Defined Dinuclear Gold Complexes for Preorganization‐Induced Selective Dual Gold Catalysis
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Vincent Vreeken Dr. Daniël L. J. Broere Anne C. H. Jans Marianne Lankelma Prof. Dr. Joost N. H. Reek Dr. Maxime A. Siegler Dr. Jarl Ivar van der Vlugt 《Angewandte Chemie (International ed. in English)》2016,55(34):10042-10046
The synthesis, reactivity, and potential of well‐defined dinuclear gold complexes as precursors for dual gold catalysis are explored. Using the preorganizing abilities of the ditopic PNHPiPr ( LH ) ligand, dinuclear AuI–AuI complex 1 and mixed‐valent AuI–AuIII complex 2 provide access to structurally characterized chlorido‐bridged cationic species 3 and 4 upon halide abstraction. For 2 , this transformation involves unprecedented two‐electron oxidation of the redox‐active ligand, generating a highly rigidified environment for the Au2 core. Facile reaction with phenylacetylene affords the σ,π‐activated phenylacetylide complex 5 . When applied in the dual gold heterocycloaddition of a urea‐functionalized alkyne, well‐defined precatalyst 3 provides high regioselectivities for the anti‐Markovnikov product, even at low catalyst loadings, and outperforms common mononuclear AuI systems. This proof‐of‐concept demonstrates the benefit of preorganization of two gold centers to enforce selective non‐classical σ,π‐activation with bifunctional substrates. 相似文献
2.
Dr. Alessandro Venturini Dr. Andrea Barbieri Prof. Dr. Joost N. H. Reek Dr. Dennis G. H. Hetterscheid 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(18):5358-5368
Catalytic water oxidation at Ir (OH)+ ( Ir =IrCp*(Me2NHC), where Cp*=pentamethylcyclopentadienyl and Me2NHC=N,N′‐dimethylimidazolin‐2‐ylidene) can occur through various competing channels. A potential‐energy surface showing these various multichannel reaction pathways provides a picture of how their importance can be influenced by changes in the oxidant potential. In the most favourable calculated mechanism, water oxidation occurs via a pathway that includes four sequential oxidation steps, prior to formation of the O?O bond. The first three oxidation steps are exothermic upon treatment with cerium ammonium nitrate and lead to formation of Ir V(?O)(O . )+, which is calculated to be the most stabile species under these conditions, whereas the fourth oxidation step is the potential‐energy‐determining step. O?O bond formation takes place by coupling of the two oxo ligands along a direct pathway in the rate‐limiting step. Dissociation of dioxygen occurs in two sequential steps, regenerating the starting material Ir (OH)+. The calculated mechanism fits well with the experimentally observed rate law: v=kobs[ Ir ][oxidant]. The calculated effective barrier of 24.6 kcal mol?1 fits well with the observed turnover frequency of 0.88 s?1. Under strongly oxidative conditions, O?O bond formation after four sequential oxidation steps is the preferred pathway, whereas under milder conditions O?O bond formation after three sequential oxidation steps becomes competitive. 相似文献
3.
Pulse Radiolysis and Ultra‐High‐Performance Liquid Chromatography/High‐Resolution Mass Spectrometry Studies on the Reactions of the Carbonate Radical with Vitamin B12 Derivatives
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Rohan S. Dassanayake Dr. Jacob T. Shelley Dr. Diane E. Cabelli Dr. Nicola E. Brasch 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(17):6409-6419
The reactions of the carbonate radical anion (CO3 . ?) with vitamin B12 derivatives were studied by pulse radiolysis. The carbonate radical anion directly oxidizes the metal center of cob(II)alamin quantitively to give hydroxycobalamin, with a bimolecular rate constant of 2.0×109 M ?1 s?1. The reaction of CO3 . ? with hydroxycobalamin proceeds in two steps. The second‐order rate constant for the first reaction is 4.3×108 M ?1 s?1. The rate of the second reaction is independent of the hydroxycobalamin concentration and is approximately 3.0×103 s?1. Evidence for formation of corrinoid complexes differing from cobalamin by the abstraction of two or four hydrogen atoms from the corrin macrocycle and lactone ring formation has been obtained by ultra‐high‐performance liquid chromatography/high‐resolution mass spectrometry (UHPLC/HRMS). A mechanism is proposed in which abstraction of a hydrogen atom by CO3 . ? from a carbon atom not involved in the π conjugation system of the corrin occurs in the first step, resulting in formation of a CoIII C‐centered radical that undergoes rapid intramolecular electron transfer to form the corresponding CoII carbocation complex for about 50 % of these complexes. Subsequent competing pathways lead to formation of corrinoid complexes with two fewer hydrogen atoms and lactone derivatives of B12. Our results demonstrate the potential of UHPLC combined with HRMS in the separation and identification of tetrapyrrole macrocycles with minor modifications from their parent molecule. 相似文献
4.
The kinetics of the oxidation of some Fe(II)–Tris Schiff base complexes by peroxydisulfate was studied spectrophotometrically in the aqueous medium and in the organic–aqua binary mixture. The inspected complexes were derived from the condensation of 2‐acetylpyridine and substituted benzylamines. The oxidation reaction of the studied complexes was followed at 303 K under pseudo–first‐order conditions. It was found that the oxidation reaction by S2O82? consists of two steps. The first step is the formation of an ion pair from the reactants, and the second step is an electron transfer from the metal center to the peroxydisulfate oxidant, with an associated peroxo bond fissure. A mechanism, based on the experimental results, was proposed, and the rate law was derived. The effect of organic solvent on the reaction rate was studied in the presence of different ratios (v/v) of methanol–water and acetone–water mixtures. Moreover, the changes in the activation barrier from water to water–methanol and water–acetone mixtures were estimated from the kinetic data. The transfer chemical potentials of the initial and transition states from water into mixed solvents were determined from solubility measurements. Solvent effects on the reaction rate were discussed in terms of initial state versus transition state solvation. 相似文献
5.
A Redox‐Active Dinuclear Platinum Complex Exhibiting Multicolored Electrochromism and Luminescence
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Dr. Masaki Yoshida Naoki Yashiro Hotaka Shitama Dr. Atsushi Kobayashi Prof. Dr. Masako Kato 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(2):491-495
A redox series of cyclometalated platinum complexes based on a dinuclear motif linked by acetamidato (aam) bridging ligands, [Pt2(μ‐aam)2(ppy)2] (ppy?=2‐phenylpyridinate ion), has been synthesized. The complexes in this series are easily oxidized and reduced by both electrochemical and chemical methods, and this is accompanied by multistep changes in their optical properties, that is, multiple color changes and luminescence. Isolation of the complexes and the structural determination of three oxidation states, +2, +2.33, and +3, have been achieved. The mixed‐valent complex, with an average oxidation state of +2.33, forms a trimer based on the dinuclear motif. The mixed‐valent complex has a characteristic color owing to intervalence transitions in the platinum chain. In contrast, the divalent complex exhibits strong red phosphorescence originating from a triplet metal‐metal‐to‐ligand charge transfer (3MMLCT) state. This study demonstrates the unique chromic behavior of a redox‐active and luminescent platinum complex. 相似文献
6.
The formation of palladium(II) complexes with aliphatic amines and their oxidation by chloramine‐T in perchloric acid medium has been studied. The spectrophotometric studies showed the formation of 1:1 and 1:2 complexes between palladium(II) and amine in absence of HClO4. An increase in [HClO4] in reaction mixture suppresses the complex formation and in presence of [HClO4] ~10?3 mol dm?3 only a 1:1 complex between palladium(II) and amine has been observed. The effect of Cl? on the complex formation has also been studied. Palladium(II)‐catalyzed oxidation of these amines by chloramine‐T showed a first‐order dependence of rate with respect to each—oxidant, substrate, catalyst, and H+. The mechanism consistent with kinetic data for the oxidation process has been proposed in absence as well as in presence of initial [Cl?]. © 2002 Wiley Periodicals, Inc. Int J Chem Kinet 34: 603–612, 2002 相似文献
7.
Venkataramana Imandi Sooraj Kunnikuruvan Dr. Nisanth N. Nair 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(15):4724-4731
The complete reaction mechanism and kinetics of the Wacker oxidation of ethene in water under low [Cl?], [PdII], and [CuII] conditions are investigated in this work by using ab initio molecular dynamics. These extensive simulations shed light on the molecular details of the associated individual steps, along two different reaction routes, starting from a series of ligand‐exchange processes in the catalyst precursor PdCl42? to the final aldehyde‐formation step and the reduction of PdII. Herein, we report that hydroxylpalladation is not the rate‐determining step and is, in fact, in equilibrium. The newly proposed rate‐determining step involves isomerization and follows the hydroxypalladation step. The mechanism proposed herein is shown to be in excellent agreement with the experimentally observed rate law and rate. Moreover, this mechanism is in consensus with the observed kinetic isotope effects. This report further confirms the outer‐sphere (anti) hydroxypalladation mechanism. Our calculations also ratify that the final product formation proceeds through a reductive elimination, assisted by solvent molecules, rather than through β‐hydride elimination. 相似文献
8.
Copper(II) and Zinc(II) Complexes of Conformationally Constrained Polyazamacrocycles as Efficient Catalysts for RNA Model Substrate Cleavage in Aqueous Solution at Physiological pH
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Daniel Bím Dr. Eva Svobodová Václav Eigner Dr. Lubomír Rulíšek Prof. Jana Hodačová 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(30):10426-10437
As part of a quest for efficient artificial catalysts of RNA phosphodiester bond cleavage, conformationally constrained mono‐ and bis‐polyazamacrocycles in which tri‐ or tetraazaalkane chains link the ortho positions of a benzene ring were synthesized. The catalytic activities of mono‐ and dinuclear copper(II) and zinc(II) complexes of these polyazamacrocycles towards cleavage of the P?O bond in 2‐hydroxypropyl‐4‐nitrophenylphosphate (HPNP) in aqueous solution at pH 7 have been determined. Only the complexes of the ligands incorporating three nitrogen atoms in a macrocycle proved to be capable of efficiently catalyzing HPNP transesterification. The dinuclear complexes were found to be approximately twice as efficient as their mononuclear counterparts, and exhibited Michaelis–Menten saturation kinetics with calculated rate constants of kcat≈10?4 s?1. By means of quantum chemical calculations (DFT/COSMO‐RS), several plausible reaction coordinates were described. By correlating the calculated barriers with the experimental kinetic data, two possible reaction scenarios were revealed, with activation free energies of 20–25 kcal mol?1. 相似文献
9.
Robert Stepi Christian R. Wick Vinzent Strobel Daniel Berger Nataa Vu
emilovi‐Alagi Marco Haumann Peter Wasserscheid Ana‐Sun
ana Smith David M. Smith 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(3):751-755
Supported ionic liquid phase (SILP) catalysis enables a highly efficient, Ru‐based, homogeneously catalyzed water‐gas shift reaction (WGSR) between 100 °C and 150 °C. The active Ru‐complexes have been found to exist in imidazolium chloride melts under operating conditions in a dynamic equilibrium, which is dominated by the [Ru(CO)3Cl3]? complex. Herein we present state‐of‐the‐art theoretical calculations to elucidate the reaction mechanism in more detail. We show that the mechanism includes the intermediate formation and degradation of hydrogen chloride, which effectively reduces the high barrier for the formation of the requisite dihydrogen complex. The hypothesis that the rate‐limiting step involves water is supported by using D2O in continuous catalytic WGSR experiments. The resulting mechanism constitutes a highly competitive alternative to earlier reported generic routes involving nucleophilic addition of hydroxide in the gas phase and in solution. 相似文献
10.
The Reaction Pathway of Cellulose Pyrolysis to a Multifunctional Chiral Building Block: The Role of Water Unveiled by a DFT Computational Investigation
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Dr. Tainah Dorina Marforio Prof. Andrea Bottoni Dr. Matteo Calvaresi Prof. Daniele Fabbri Dr. Pietro Giacinto Prof. Francesco Zerbetto 《Chemphyschem》2016,17(23):3948-3953
LAC (hydroxylactone (1R,5S)‐1‐hydroxy‐3,6‐dioxabicyclo[3.2.1]octan‐2‐one) is one of the most interesting products of the pyrolysis of cellulose and represents a useful chiral building block in organic synthesis. A computational investigation at the DFT level on the mechanism of formation of LAC shows that this species can be obtained following two reaction paths, path A and path B , starting from a well‐known pyrolysis product (ascopyrone P). A series of internal rearrangements involving in all cases a proton transfer leads directly to LAC ( path B ). An alternative path ( path A ) can be also followed. From this path, via a “gate” connecting the two reaction channels, it is possible to reach path B and form LAC. In both cases, the rate‐determining step of the process is the initial keto‐enol isomerization. We found that water, which is present in the reaction mixture, “catalyzes” the reaction by assisting the proton transfers present in all the steps of the process. In particular, water lowers the barrier of the rate‐determining step that becomes 40.9 kcal mol?1 (79.4 kcal mol?1 in the absence of water). The corresponding computed rate constant is 4.3×10 s?1 at 500 °C, a value which is consistent with the presence of LAC in the absence of metal catalysts. The results of this study on the non‐catalyzed process underpin the important role played by water in the formation of pyrolysis products of cellulose where proton transfer is a key mechanistic step. 相似文献
11.
Anodic Hydrazine Oxidation Assists Energy‐Efficient Hydrogen Evolution over a Bifunctional Cobalt Perselenide Nanosheet Electrode
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Jun‐Ye Zhang Prof. Dr. Hongming Wang Yifan Tian Prof. Dr. Ya Yan Qi Xue Ting He Prof. Dr. Hongfang Liu Dr. Chundong Wang Prof. Dr. Yu Chen Prof. Dr. Bao Yu Xia 《Angewandte Chemie (International ed. in English)》2018,57(26):7649-7653
Water electrolysis is a promising source of hydrogen; however, technological challenges remain. Intensive efforts have focused on developing highly efficient and earth‐abundant electrocatalysts for water splitting. An effective strategy is proposed, using a bifunctional tubular cobalt perselenide nanosheet electrode, in which the sluggish oxygen evolution reaction is substituted with anodic hydrazine oxidation so as to assist energy‐efficient hydrogen production. Specifically, this electrode produces a current density of 10 mA cm?2 at ?84 mV for hydrogen evolution and ?17 mV for hydrazine oxidation in 1.0 m KOH and 0.5 m hydrazine electrolyte. An ultralow cell voltage of only 164 mV is required to generate a current density of 10 mA cm?2 for 14 hours of stable water electrolysis. 相似文献
12.
13.
Ferran Acuña‐Parés Zoel Codolà Dr. Miquel Costas Dr. Josep M. Luis Dr. Julio Lloret‐Fillol 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(19):5696-5707
Density functional theory (DFT) is employed to: 1) propose a viable catalytic cycle consistent with our experimental results for the mechanism of chemically driven (CeIV) O2 generation from water, mediated by nonheme iron complexes; and 2) to unravel the role of the ligand on the nonheme iron catalyst in the water oxidation reaction activity. To this end, the key features of the water oxidation catalytic cycle for the highly active complexes [Fe(OTf)2(Pytacn)] (Pytacn: 1‐(2′‐pyridylmethyl)‐4,7‐dimethyl‐1,4,7‐triazacyclononane; OTf: CF3SO3?) ( 1 ) and [Fe(OTf)2(mep)] (mep: N,N′‐bis(2‐pyridylmethyl)‐N,N′‐dimethyl ethane‐1,2‐diamine) ( 2 ) as well as for the catalytically inactive [Fe(OTf)2(tmc)] (tmc: N,N′,N′′,N′′′‐tetramethylcyclam) ( 3 ) and [Fe(NCCH3)(MePy2CH‐tacn)](OTf)2 (MePy2CH‐tacn: N‐(dipyridin‐2‐yl)methyl)‐N′,N′′‐dimethyl‐1,4,7‐triazacyclononane) ( 4 ) were analyzed. The DFT computed catalytic cycle establishes that the resting state under catalytic conditions is a [FeIV(O)(OH2)(LN4)]2+ species (in which LN4=Pytacn or mep) and the rate‐determining step is the O?O bond‐formation event. This is nicely supported by the remarkable agreement between the experimental (ΔG≠=17.6±1.6 kcal mol?1) and theoretical (ΔG≠=18.9 kcal mol?1) activation parameters obtained for complex 1 . The O?O bond formation is performed by an iron(V) intermediate [FeV(O)(OH)(LN4)]2+ containing a cis‐FeV(O)(OH) unit. Under catalytic conditions (CeIV, pH 0.8) the high oxidation state FeV is only thermodynamically accessible through a proton‐coupled electron‐transfer (PCET) process from the cis‐[FeIV(O)(OH2)(LN4)]2+ resting state. Formation of the [FeV(O)(LN4)]3+ species is thermodynamically inaccessible for complexes 3 and 4 . Our results also show that the cis‐labile coordinative sites in iron complexes have a beneficial key role in the O?O bond‐formation process. This is due to the cis‐OH ligand in the cis‐FeV(O)(OH) intermediate that can act as internal base, accepting a proton concomitant to the O?O bond‐formation reaction. Interplay between redox potentials to achieve the high oxidation state (FeV?O) and the activation energy barrier for the following O?O bond formation appears to be feasible through manipulation of the coordination environment of the iron site. This control may have a crucial role in the future development of water oxidation catalysts based on iron. 相似文献
14.
Theoretical Studies on the Asymmetric Baeyer–Villiger Oxidation Reaction of 4‐Phenylcyclohexanone with m‐Chloroperoxobenzoic Acid Catalyzed by Chiral Scandium(III)–N,N′‐Dioxide Complexes
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Dr. Na Yang Dr. Zhishan Su Prof. Dr. Xiaoming Feng Prof. Dr. Changwei Hu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(19):7264-7277
The mechanism and enantioselectivity of the asymmetric Baeyer–Villiger oxidation reaction between 4‐phenylcyclohexanone and m‐chloroperoxobenzoic acid ( m ‐CPBA ) catalyzed by ScIII–N,N′‐dioxide complexes were investigated theoretically. The calculations indicated that the first step, corresponding to the addition of m ‐CPBA to the carbonyl group of 4‐phenylcyclohexanone, is the rate‐determining step (RDS) for all the pathways studied. The activation barrier of the RDS for the uncatalyzed reaction was predicted to be 189.8 kJ mol?1. The combination of an ScIII–N,N′‐dioxide complex and the m ‐CBA molecule can construct a bifunctional catalyst in which the Lewis acidic ScIII center activates the carbonyl group of 4‐phenylcyclohexanone while m ‐CBA transfers a proton, which lowers the activation barrier of the addition step (RDS) to 86.7 kJ mol?1. The repulsion between the m‐chlorophenyl group of m ‐CPBA and the 2,4,6‐iPr3C6H2 group of the N,N′‐dioxide ligand, as well as the steric hindrance between the phenyl group of 4‐phenylcyclohexanone and the amino acid skeleton of the N,N′‐dioxide ligand, play important roles in the control of the enantioselectivity. 相似文献
15.
Electrocatalytic Water Oxidation by a Dinuclear Copper Complex in a Neutral Aqueous Solution
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Xiao‐Jun Su Meng Gao Prof. Dr. Lei Jiao Prof. Dr. Rong‐Zhen Liao Prof. Per E. M. Siegbahn Prof. Dr. Jin‐Pei Cheng Prof. Dr. Ming‐Tian Zhang 《Angewandte Chemie (International ed. in English)》2015,54(16):4909-4914
Electrocatalytic water oxidation using the oxidatively robust 2,7‐[bis(2‐pyridylmethyl)aminomethyl]‐1,8‐naphthyridine ligand (BPMAN)‐based dinuclear copper(II) complex, [Cu2(BPMAN)(μ‐OH)]3+, has been investigated. This catalyst exhibits high reactivity and stability towards water oxidation in neutral aqueous solutions. DFT calculations suggest that the O? O bond formation takes place by an intramolecular direct coupling mechanism rather than by a nucleophilic attack of water on the high‐oxidation‐state CuIV?O moiety. 相似文献
16.
Bimetallic Cyclometalated Iridium(III) Diastereomers with Non‐Innocent Bridging Ligands for High‐Efficiency Phosphorescent OLEDs
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Dr. Yonghao Zheng Dr. Andrei S. Batsanov Dr. Mark A. Fox Dr. Hameed A. Al‐Attar Khalid Abdullah Dr. Vygintas Jankus Prof. Martin R. Bryce Prof. Andrew P. Monkman 《Angewandte Chemie (International ed. in English)》2014,53(43):11616-11619
Two phosphorescent dinuclear iridium(III) diastereomers (ΛΔ/ΔΛ) and (ΛΛ/ΔΔ) are readily separated by making use of their different solubilities in hot hexane. The bridging diarylhydrazide ligand plays an important role in the electrochemistry and photophysics of the complexes. Organic light‐emitting devices (OLEDs) that use these complexes as the green‐emissive dopants in solution‐processable single‐active‐layer architectures feature electroluminescence efficiencies that are remarkably high for dinuclear metal complexes, achieving maximum values of 37 cd A?1, 14 lm W?1, and 11 % external quantum efficiency. 相似文献
17.
Water Oxidation by Ruthenium Complexes Incorporating Multifunctional Bipyridyl Diphosphonate Ligands
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Yan Xie Dr. David W. Shaffer Dr. Anna Lewandowska‐Andralojc Dr. David J. Szalda Dr. Javier J. Concepcion 《Angewandte Chemie (International ed. in English)》2016,55(28):8067-8071
We describe herein the synthesis and characterization of ruthenium complexes with multifunctional bipyridyl diphosphonate ligands as well as initial water oxidation studies. In these complexes, the phosphonate groups provide redox‐potential leveling through charge compensation and σ donation to allow facile access to high oxidation states. These complexes display unique pH‐dependent electrochemistry associated with deprotonation of the phosphonic acid groups. The position of these groups allows them to shuttle protons in and out of the catalytic site and reduce activation barriers. A mechanism for water oxidation by these catalysts is proposed on the basis of experimental results and DFT calculations. The unprecedented attack of water at a neutral six‐coordinate [RuIV] center to yield an anionic seven‐coordinate [RuIV?OH]? intermediate is one of the key steps of a single‐site mechanism in which all species are anionic or neutral. These complexes are among the fastest single‐site catalysts reported to date. 相似文献
18.
Dr. Martín Regueiro‐Figueroa Dr. Gabriele A. Rolla Dr. David Esteban‐Gómez Dr. Andrés de Blas Dr. Teresa Rodríguez‐Blas Prof. Mauro Botta Dr. Carlos Platas‐Iglesias 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(52):17300-17305
Stable Mn2+ mono‐ and binuclear complexes containing pentadentate 6,6′‐((methylazanediyl)bis(methylene))dipicolinic acid coordinating units give remarkably high relaxivities due to the presence of two inner‐sphere water molecules. The mononuclear derivative binds human serum albumin (HSA) with an association constant of 3372 M ?1, which results in the replacement of the coordinated water molecules by donor atoms of protein residues. The dinuclear analogue also binds HSA while leaving one of the Mn2+ centres exposed to the solvent with two coordinated water molecules. Thus, this complex shows remarkably high relaxivities upon protein binding (39.0 mM ?1 s?1 per Mn, at 20 MHz and 37 °C). 相似文献
19.
Chencheng Dai Yuanmiao Sun Gao Chen Adrian C. Fisher Zhichuan J. Xu 《Angewandte Chemie (International ed. in English)》2020,59(24):9418-9422
Nitrates are widely used as fertilizer and oxidizing agents. Commercial nitrate production from nitrogen involves high‐temperature‐high‐pressure multi‐step processes. Therefore, an alternative nitrate production method under ambient environment is of importance. Herein, an electrochemical nitrogen oxidation reaction (NOR) approach is developed to produce nitrate catalyzed by ZnFexCo2?xO4 spinel oxides. Theoretical and experimental results show Fe aids the formation of the first N?O bond on the *N site, while high oxidation state Co assists in stabilizing the absorbed OH? for the generation of the second and third N?O bonds. Owing to the concerted catalysis, the ZnFe0.4Co1.6O4 oxide demonstrates the highest nitrate production rate of 130±12 μmol h?1 gMO?1 at an applied potential of 1.6 V versus the reversible hydrogen electrode (RHE). 相似文献
20.
The reaction between Au(I), generated by reaction of thallium(I) with Au(III), and peroxydisulphate was studied in 5 mol dm?3 hydrochloric acid. The reaction proceeds with the formation of an ion‐pair between peroxydisulphate and chloride ion as the Michealis–Menten plot was linear with intercept. The ion‐pair thus formed oxidizes AuCl2? in a slow two‐electron transfer step without any formation of free radicals. The ion‐pair formation constant and the rate constant for the slow step were determined as 113 ± 20 dm?3 mol?1 and 5.0 ± 1.0 × 10?2 dm3 mol?1 s?1, respectively. The reaction was retarded by hydrogen ion, and formation of unreactive protonated form of the reductant, HAuCl2, causes the rate inhibition. From the hydrogen ion dependence of the reaction rate, the protonation constant was calculated to be as 0.6 ± 0.1 dm3 mol?1. The activation parameters were determined and the values support the proposed mechanism. © 2002 Wiley Periodicals, Inc. Int J Chem Kinet 34: 589–594, 2002 相似文献