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1.
The Belousov‐Zhabotinsky (BZ) reaction of bromate ion with 2‐ketoglutaric acid (KGA) in aqueous sulfuric acid catalyzed by Ce(III), Mn(II), or Fe(phen)32+ ion exhibits sustained barely damped oscillations under aerobic conditions. In general, the reaction oscillates without an induction period. Fe(phen)32+ ion behaves differently from Ce(III) and Mn(II) ions in catalyzing this oscillating system. The gem‐diol form of KGA exhibits different behavior from that of the keto form of KGA in the BZ reaction. The kinetics and mechanism of the reaction of KGA with Ce(IV), Mn(III), or Fe(phen)33+ ion was investigated. The order of relative reactivities of metal ions toward reaction with KGA is Mn(III) > Ce(IV) ≫ Fe(phen)33+. Experimental results are rationalized. © 2001 John Wiley & Sons, Inc. Int J Chem Kinet 33: 101–107, 2001  相似文献   

2.
The Ce(III)‐, Mn(II)‐, or ferroin (Fe(phen)32+)‐catalyzed reaction of bromate ion and pyruvic acid (PA) or its dimer exhibits oscillatory behavior. Both the open‐chain dimer (parapyruvic acid, γ‐methyl‐γ‐hydroxyl‐α‐keto‐glutaric acid, DPA1) and the cyclic‐form dimer (α‐keto‐γ‐valerolactone‐γ‐carboxylic acid, DPA2) show more sustained oscillations than PA monomer. Ferroin behaves differently from Ce(III) or Mn(II) ion in catalyzing these oscillating systems. The kinetics of reactions of PA, 3‐brompyruvic acid (BrPA), DPA1, or DPA2 with Ce(IV), Mn(III), Fe(phen)33+ ion were investigated. The order of relative reactivity of pyruvic acids toward reaction with Ce(IV), Mn(III), or Fe(phen)33+ ion is DPA2 > DPA1 > BrPA > PA and that of metal ions toward reaction with pyruvic acids is Mn(III) > Ce(IV) > Fe(phen)33+. The rates of bromination reactions of pyruvic acids are independent of the concentration of bromine and the order of reactivity toward bromination is (DPA1, DPA2) > BrPA > PA. Experimental results are rationalized. © 2000 John Wiley & Sons, Inc. Int J Chem Kinet 32: 408–418, 2000  相似文献   

3.
In a stirred batch experiment and under aerobic conditions, ferroin (Fe(phen)32+) behaves differently from Ce(III) or Mn(II) ion as a catalyst for the Belousov‐Zhabotinsky (BZ) reaction with allylmalonic acid (AMA). The effects of bromate ion, AMA, metal‐ion catalyst, and sulfuric acid on the oscillating pattern were investigated. The kinetics of the reaction of AMA with Ce(IV), Mn(III), or Fe(phen)33+ ion was studied under aerobic or anaerobic conditions. The order of reactivity of metal ions toward reaction with AMA is Fe(phen)33+ > Mn(III) > Ce(IV) under aerobic conditions whereas it is Mn(III) > Ce(IV) > Fe(phen)33+ under anaerobic conditions. Under aerobic or anaerobic conditions, the order of reactivity of RCH(CO2H)2 (R = H (MA), Me (MeMA), Et (EtMA), allyl (AMA), n‐Bu (BuMA), Ph (PhMA), and Br (BrMA)) is PhMA > MA > BrMA > AMA > MeMA > EtMA > BuMA toward reaction with Ce(IV) ion and it is MA > PhMA > BrMA > MeMA > AMA > EtMA > BuMA toward reaction with Mn(III) ion. Under aerobic conditions, the order of reactivity of RCH(CO2H)2 toward reaction with Fe(phen)33+ ion is PhMA > BrMA > (MeMA, AMA) > (BuMA, EtMA) > MA. The experiment results are rationalized.  相似文献   

4.
In a stirred batch experiment, ferroin (Fe(phen)32+) behaves differently from Ce(III) as a catalyst for the Belousov-Zhabotinsky reaction with ethyl- or n-butyl-malonic acid (EtMA or BuMA) The effects of bromate ion, organic substrate, metal-ion catalyst, and sulfuric acid on the oscillating pattern were investigated. The kinetics of the reactions of methylmalonic acid (MeMA), bromomethyl-malonic acid (BrMeMA), EtMA, bromoethylmalonic acid (BrEtMA), BuMA, bromo(n-butyl)malonic acid (BrBuMA) with Ce(IV) or Fe(phen)33+ ion were studied. Under aerobic or anaerobic conditions, the order of reactivity toward Ce(IV) oxidation is MeMA > EtMA > BuMA > BrMeMA >> (BrEtMA, BrBuMA). Under aerobic conditions, the order of reactivity toward reacting with Fe(phen)33+ ion is MeMA > (BuMA, EtMA) >> (BrMeMA, BrEtMA, BrBuMA). The experimental results are rationalized. © 1996 John Wiley & Sons, Inc.  相似文献   

5.
The oscillating reaction involving organic gallic acid (GA), potassium bromate, and a metal ion complex has been reinvestigated. In contrast to other previous reports, this oscillating reaction is catalyzed by the [Fe(phen)n]2+ ion (phen = 1,10-o-phenanthroline, n=1, 2, 3) rather than by the cerium ion. The characteristics of the oscillations depend on the temperature and on the concentrations of the potassium bromate, gallic acid, [Fe(phen)n]2+, and sulfuric acid. A cyclic voltammetric study indicates that the redox potential and the reversibility of the [Fe(phen)n]2+/3+ couple play a major role in catalyzing this oscillating system.  相似文献   

6.
In a stirred batch reactor, the Ce(III)- or Mn(II)-catalyzed Belousov–Zhabotinsky reaction with mixed organic acid/ketone substrates exhibits oscillatory behavior. The organic acids studied here are: dl-mandelic acid (MDA), dl-4-bromomandelic acid (BMDA), and dl-4-hydroxymandelic acid (HMDA), and the ketones are: acetone (Me2CO), methyl ethyl ketone (MeCOEt), diethyl ketone (Et2CO), acetophenone (MeCOPh), and cyclohexanone ((CH2)5CO). The effects of bromate ion, organic acid, ketone, metal-ion catalyst, and sulfuric acid concentrations on the oscillatory patterns are investigated. Both conventional and stopped-flow methods are applied to study the kinetics of the oxidation reactions of the above organic acids by Ce(IV) or Mn(III) ion. The order of relative reactivities of the oxidation reactions of organic acids in 1 M H2SO4 is Mn(III)(SINGLEBOND)HMDA reaction>Ce(IV)(SINGLEBOND)HMDA reaction>Mn(III)(SINGLEBOND)BMDA, reaction>Mn(III)(SINGLEBOND)MDA reaction>Ce(IV)(SINGLEBOND)BMDA reaction>Ce(IV)(SINGLEBOND)MDA reaction. Spectrophotometric study of the bromination reactions of the above ketones shows that these reactions are zero-order with respect to bromine and first-order with respect to ketone and that ketone enolization is the rate-determining step. The order of relative rates of bromination or enolization reactions of ketones in 1 M H2SO4 is (CH2)5CO≫(MeCOEt, Et2CO, Me2CO)>MeCOPh. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet:30: 595–604, 1998  相似文献   

7.
The kinetics of the base hydrolysis of Fe(phen)32+ and Fe(bipy)32+ (phen = 1,10‐phenanthroline and bipy = 2,2'‐bipyridine) in some aqueous alcohol mixtures at ambient and elevated pressures (up to 1kbar) have been monitored spectrophotometrically at 25.0°C. For a given pressure, the alcohol cosolvent increases the rate of reaction relative to the reaction in a wholly aqueous medium. In all cases, increasing pressure causes rate retardation and derived volumes of activation for the reactions in aqueous solvent mixtures vary between +15 and +25 cm3 mol−1, indicating that solvation changes of a different magnitude occur upon reaching the transition state from those occurring for the reactions in aqueous medium. Since the reaction has been established earlier to be nucleophilic attack of the incoming hydroxide ion, the volumes of activation signify marked increases in the loss of electrostricted solvent from the vicinities of the hydroxide ion and the iron(II) complex ions. © 2000 John Wiley & Sons, Inc. Int J Chem Kinet 32: 263–270, 2000  相似文献   

8.
The outer-sphere electron-transfer reactions between [Co(III)(NH3)5L] (CIO4)3 [L = polyethyleneimine (PEI), L = NH3(Amm)] or cis-[Co(III)(en)2L′Cl]Cl2 [L′ = poly-N-vinyl-2-methylimidazole(PVI), poly-4-vinylpyridine (PVP), N-ethylimidazole (NEI), pyridine (Py)] and various Fe(II) were studied. In the reaction with Fe(II)-(phen)32+, the reactivity of Co(III)–PEI was smaller than that of Co(III)–Amm due to the larger electrostatic repulsion. On the other hand, the reactivity of Co(III)–PEI was larger by a factor of 80 in the reaction with Fe(II)(H2O)62+. From the results of rapid-scanning spectroscopy, the higher reactivity of Co(III)–PEI is caused by the coordination of free ethyleneimine residues in the Co(III)–PEI to Fe(II)–ion. Further more, the hydrophobic interaction between heteroaromatic polymer ligands and Fe(II)-(phen)32+ brought about the higher reactivities of Co(III)–PVI and Co(III)–PVP. Three interactions caused by the essential properties of polymers are discussed in relation to conformational changes.  相似文献   

9.
Chemically modified zeolite Y (NaY) particles and their resulting modified electrodes were prepared with acridinium (AcH+), iron(II) and 1,10‐phenanthroline (phen) for energetic studies. According to diffuse reflectance absorption spectroscopy and cyclic voltammetry, AcH+ and Fe(phen)32+ were successfully entrapped in the zeolite particles. Transient emission spectra measurements showed that the life time of AcH+* in the zeolite particles (to 35 ns; λex 365 nm; λem 500 nm) was greatly reduced upon incorporating Fe(phen)32+ and Fe2+. The fast de cay of AcH+*(NaY) suggested that a reductive quench was likely to take place in the zeolite particle. Probably due to a size‐exclusion effect, the bulky electron donor, N, N‐diethyl‐2‐methyl‐1,4‐phenylenediamine (DEPD), revealed a difficulty in reaching the photosensitizer, AcH+, in side the zeolite particle. As a consequence, the in significant photocurrent for the oxidation of DEPD was from the NaY|AcH+ electrode. However, if Fe2+ and Fe(phen)32+ were incorporated, the photocurrent would become more significant. Closer examinations, in addition, showed that the photooxidaton of DEPD occurred more rapidly on the NaY|AcH+|Fe(phen)32+ electrode, compared to the NaY|AcH+|Fe2+ electrode. This difference apparently results from a greater gap in energetics between DEPD and Fe(phen)33+(NaY) than that between DEPD and Fe3+(NaY). Due to this effect, a greater amount of indophenol blue, derived from the coupling reaction of the oxidized DEPD with 1‐naphthol, was formed and de posited on the NaY|AcH+|Fe(phen)32+modified electrode. Thanks to this photo‐induced charge‐transfer reaction, the NaY|AcH+|Fe(phen)32+ particle showed an application potential in image recording.  相似文献   

10.
Formation thermodynamics of binary and ternary lanthanide(III) (Ln = La, Ce, Nd, Eu, Gd, Dy, Tm, Lu) complexes with 1,10-phenanthroline (phen) and the chloride ion have been studied by titration calorimetry and spectrophotometry in N,N-dimethyl-formamide (DMF) containing 0.2 mol-dm–3 (C2H5)4NClO4 as a constant ionic medium at 25°C. In the binary system with 1,10-phenanthroline, the Ln(phen)3+ complex is formed for all the lanthanide(III) ions examined. The reaction enthalpy and entropy values for the formation of Ln(phen)3+ decrease in the order La > Ce > Nd, then increase in the order Nd < Eu < Gd < Dy, and again decrease in the order Dy > Tm > Lu. The variation is explained in terms of the coordination structure of Ln(phen)3+ that changes from eight to seven coordination with decreasing ionic radius of the metal ion. In the ternary Ln3+-Cl-phen system, the formation of LnCl(phen)2+, LnCl2(phen)+, and LnCl3(phen) was established for cerium(III), neodymium(III), and thulium(III), and their formation constants, enthalpies, and entropies were obtained. The enthalpy and entropy values are also discussed from the structural point of view.  相似文献   

11.
The formation kinetics of ferroin is studied under varied acid conditions at 25°C and fixed ionic strength (0.48 mol dm?3) under pseudo‐first‐order conditions with respect to Fe2+ by using the stopped‐flow technique. The reaction followed is first and third order with respect to Fe2+ and 1,10‐phenanthroline (phen)T, respectively. Increasing the acid concentration retarded the reaction, and the reaction rate showed a positive salt effect. The rate‐limiting step involved the complexation of the phen or protonated phen with [Fe(phen)2]2+ complex ion, leading to formation of [Fe(phen)3]2+ ion. The observed retardation of the reaction rate with increasing [H+]0 is due to the increased [phenH+]eq and low reactivity of phenH+ with [Fe(phen)2]2+ complex ion. Simulated curves for the acid variation experiments agreed well with the corresponding experimental curves and the estimated rate coefficients supporting the proposed mechanism. Relatively low energy of activation (26 kJ mol?1) and high negative entropy of activation (?159.8 J K?1 mol?1) agree with the proposed mechanism and the formation of compact octahedral complex ion. © 2008 Wiley Periodicals, Inc. 40: 515–523, 2008  相似文献   

12.
The kinetics of the bromate oxidation of tris(1,10-phenanthroline)iron(II) (Fe(phen)32+) and aquoiron(II) (Fe2+ (aq)) have been studied in aqueous sulfuric acid solutions at μ = 1.0M and with Fe(II) complexes in great excess. The rate laws for both reactions generally can be described as -d [Fe(II)]/6dt = d[Br?]/dt = k[Fe(II)] [BrO?3] for [H+]0 = 0.428–1.00M. For [BrO?3]0 = 1.00 × 10?4M. [Fe2+]0 = (0.724–1.45)x 10?2 M, and [H+]0 = 1.00M, k = 3.34 ± 0.37 M?1s?1 at 25°. For [BrO?3]0 = (1.00–1.50) × 10?4M, [Fe2+]0 = 7.24 × 10?3M ([phen]0 = 0.0353M), and [H+]0 = 1.00M, k = (4.40 ± 0.16) × 10?2 M?1s?1 at 25°. Kinetic results suggest that the BrO?3-Fe2+ reaction proceeds by an inner-sphere mechanism while the BrO?3-Fe(phen)32+ reaction by a dissociative mechanism. The implication of these results for the bromate-gallic acid and other bromate oscillators is also presented.  相似文献   

13.
The oxidation of D ‐mannitol by cerium(IV) has been studied spectrophotometrically in aqueous sulfuric acid medium at 25°C at constant ionic strength of 1.60 mol dm?3. A microamount of ruthenium(III) (10?6 mol dm?3) is sufficient to enhance the slow reaction between D ‐mannitol and cerium(IV). The oxidation products were identified by spot test, IR and GC‐MS spectra. The stoichiometry is 1:4, i.e., [D ‐mannitol]: [Ce(IV)] = 1:4. The reaction is first order in both cerium(IV) and ruthenium(III) concentrations. The order with respect to D ‐mannitol concentration varies from first order to zero order as the D ‐mannitol concentration increases. Increase in the sulfuric acid concentration decreases the reaction rate. The added sulfate and bisulfate decreases the rate of reaction. The active species of oxidant and catalyst are Ce(SO4)2 and [Ru(H2O)6]3+, respectively. A possible mechanism is proposed. The activation parameters are determined with respect to a slow step and reaction constants involved have been determined. © 2010 Wiley Periodicals, Inc. Int J Chem Kinet 42: 440–452, 2010  相似文献   

14.
The title compound, [Mn(C12H8N2)2(H2O)2](C4H4O4S)·[Mn(C4H4O4S)(C12H8N2)2]·13H2O, contains one dianion of thio­diglycolic acid (tdga2−) and two independent man­ganese(II) moieties, viz. [Mn(phen)2(H2O)2]2+ and [Mn(tdga)(phen)2], where phen is 1,10‐phenanthroline. The MnII atoms are octahedrally coordinated by four N atoms of two bidentate phen ligands [Mn—N = 2.240 (2)–2.3222 (19) Å] and either two water O atoms or two tdga carboxyl O atoms [Mn—O = 2.1214 (17)–2.1512 (17) Å]. The tdga ligand chelates as an O,O′‐bidentate ligand, forming an eight‐membered ring with one Mn atom. The free tdga2− dianion is hydrogen bonded to an [Mn(phen)2(H2O)2]2+ ion, with O⋯O distances of 2.606 (2) and 2.649 (2) Å. The crystal structure is further stabilized by an extensive network of hydrogen bonds involving 13 water mol­ecules.  相似文献   

15.
The electronic structures of the systems [Mn(phen)2]2+ (I), Mn(HCO3 )2(H2O)3 (II), [Mn(phen)2(H2O)O2]2+ (III) and [Mn(phen)2O2]2+ (IV) have been calculated by the IEHM method. The change in the energy barrier for the activation of O2 (−4.59 eV (III), −4.69 eV (IV) for the elementary step has been calculated using the vibronic activation theory. The formation of an adduct of molecular oxygen with II is shown to be unlikely. Deceased. Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 33, No. 3, pp. 192–195, May–June, 1997.  相似文献   

16.
The title compound, [Ru(C12H8N2)3]2[Fe(NCS)4](ClO4)2, crystallizes in a tetragonal chiral space group (P41212) and the assigned absolute configuration of the optically active molecules was unequivocally confirmed. The Δ‐[RuII(phen)3]2+ complex cations (phen is 1,10‐phenanthroline) interact along the 41 screw axis parallel to the c axis, with an Ru...Ru distance of 10.4170 (6) Å, and in the ab plane, with Ru...Ru distances of 10.0920 (6) and 10.0938 (6) Å, defining a primitive cubic lattice. The Fe atom is situated on the twofold axis diagonal in the ab plane. The supramolecular architecture is supported by C—H...O interactions between the [RuII(phen)3]2+ cation and the disordered perchlorate anion. This study adds to the relatively scarce knowledge about intermolecular interactions between [Ru(phen)3]2+ ions in the solid state, knowledge that eventually may also lead to a better understanding of the solution state interactions of this species; these are of immense interest because of the photochemical properties of these ions and their interactions with DNA.  相似文献   

17.
A chiral coordination compound {(Δ)[Fe(II)(phen)3][(Δ)Fe(III)(C2O4)3](NH4)(H2O)3(DMF)}n (phen = 1,10‐phenanthroline), (DMF = N,N'‐Dimethylformamide), has been synthesized, and the structure has been revealed by infrared spectroscopy and X‐ray single‐crystal diffraction. The framework consists of two chiral subunits. One subunit (Δ)[(Fe(III)(C2O4)3]3? which as host anion forms a chiral porous three‐dimensional supermolecular network with lattice water, lattice DMF and lattice ammonium cation through hydrogen bonds. And then the other is Δ[Fe(II)(phen)3]2+ which as guest cation fills in the chiral cavity located in the previously mentioned host porous network.  相似文献   

18.
The oxidation of cis‐diaquabis(1,10‐phenanthroline)chromium(III) [cis‐CrIII(phen)2(H2O)2]3+ by ‐bromosuccinimide (NBS) to yield cis‐dioxobis(1,10‐phenanthroline)chromium(V) has been studied spectrophotometrically in the pH 1.57–3.56 and 5.68–6.68 ranges at 25.0°C. The reaction displayed biphasic kinetics at pH < 4.0 and a simple first order at the pH > 5.0. In the low pH range, the reaction proceeds by two successive steps; the first faster step corresponds to the oxidation of Cr(III) to Cr(IV), and the second slower one corresponds to the oxidation of Cr(IV) to Cr(V), the final product of the reaction. The formation of both Cr(IV) and Cr(V) has been detected by electron spin resonance (ESR). The ESR clearly showed the formation and decay of Cr(IV) as well as the formation of Cr(V). Each oxidation process exhibited a first‐order dependence on the initial [Cr(III)]. The pseudo–first‐order rate constants k34 and k45, for the faster and slower steps, respectively, were obtained by a computer program using Origin7.0. Both rate constants showed first‐order dependence on [NBS] and increased with increasing pH.  相似文献   

19.
The study of manganese complexes as water‐oxidation catalysts (WOCs) is of great interest because they can serve as models for the oxygen‐evolving complex of photosystem II. In most of the reported Mn‐based WOCs, manganese exists in the oxidation states III or IV, and the catalysts generally give low turnovers, especially with one‐electron oxidants such as CeIV. Now, a different class of Mn‐based catalysts, namely manganese(V)–nitrido complexes, were explored. The complex [MnV(N)(CN)4]2− turned out to be an active homogeneous WOC using (NH4)2[Ce(NO3)6] as the terminal oxidant, with a turnover number of higher than 180 and a maximum turnover frequency of 6 min−1. The study suggests that active WOCs may be constructed based on the MnV(N) platform.  相似文献   

20.
The title compound, [Cu(C2N3)2(C12H8N2)]n, has a sheet‐like structure, built by [Cu(phen)(dca)2]n (phen is 1,10‐phenanthroline and dca is dicyan­amide) chains which are interconnected by secondary long Cu—N bonds between the chains. The Cu2+ ion is in a distorted tetragonal bipyramidal (5 + 1) coordination environment. The sheets stack into the three‐dimensional crystal structure through aromatic interactions between the coordinated phen ligands of adjacent sheets.  相似文献   

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