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1.
Summary Oxidation of Mn
aq
2+
by HSO
5
–
in acetate buffer to manganese(IV) is autocatalytic, and obeys a rate expression of the general form -d[MnII]/dt = k0[MnII] + k1[MnII][MnOx]. The first-order (k0) and heterogenetic (k1) rate constants show first-order dependences on [HSO
5
–
] and on 1/[H+]. The reaction is catalyzed by the addition of the chelating ligand glycine; k1 shows a first-order dependence on [glycine] at a fixed pH. This catalysis is ascribed to complexation, whereby the redox potential for Mn(gly)
n
(2–n)+
is lower than that for Mn
aq
2+
, facilitating oxidation. The stoichiometry of the reaction is Mn2+: HSO
5
–
= 11, and the manganese(IV) oxide formed is of battery-active grade. Purity of the recovered product is not affected by the presence of high concentrations of natural sugars in the initial solution. 相似文献
2.
Summary The kinetics of reversible complexation of NiII and CoII with iminodiacetato(pentaammine)cobalt(III), [(NH3)5-Co(idaH2)]3+ and NiII with iminodiacetato(tetraammine)-cobalt(III), [(NH3)4Co(idaH)]2+, have been investigated by the stopped-flow technique at 25 °C, pH = 5.7–6.9 and I = 0.3 mol dm –3. The reaction paths (NH3)5Co(idaH)2++M2+(NH3)5Co(ida)M3++H+ (NH3)5Co(ida)++M2+(NH3)5Co(ida)M3+ (NH3)4Co(ida)++Ni2+(NH3)4Co(ida)Ni3+ have been identified (idaH = N+H2(CH2CO2)2H, ida = NH(CH2COO)2–]. The rate parameters for the formation and dissociation of the binuclear species are reported. The data are essentially consistent with an I
d mechanism. The dissociation rate constants of the binuclear species indicate that Ni2+ and Co2+ are chelated by the coordinated iminodiacetate moiety. 相似文献
3.
Summary The copper(III)-imine-oxime complexes [CuIII(Enio)]+ and [CuIII(Pre)]+ {EnioH2 =N,N-ethylene bis(isonitrosoacetylacetoneimine) and PreH2 = N,N-propylene bis (isonitrosoacetylacetoneimine)} react very rapidly with iodide. The rate law under fixed conditions for the reaction is given by the equation: –d[CuIII]/dt = (2k2[I–] + 2k3[I–]2)[CuIII] The [CuIII(Enio)]+ reaction was pH-independent whereas the [Cu (Pre)]+ reaction rate increased with increasing pH. Both the k2 and the k3 pathways are believed to involve one-electron transfer. An inner-sphere mechanism may operate in the pathway, first-order in [I–]. 相似文献
4.
Using flow microcalorimetry, the ion association reaction M2+(aq)+Fe(CN)
6
4–
(aq)=MFe(CN)
6
2–
(aq) (M=Ca, Mg) has been studied at 25°C over the ionic strength range 0.02 to 0.08 mol-dm–3. Analyses of the data to obtain Ho, the enthalpy change at infinite dilution, are described. The value obtained for Ho is sensitive to the kind of functions used to correct for non-ideal behavior. 相似文献
5.
The solubility of calcium isosaccharinate Ca(ISA)2(c) was determined at 23°C as a function of pH (1–14) and calcium ion molality (0.03–0.52). The similarity of solubility from the over- and undersaturation directions for different equilibration periods indicated that equilibrium in these solutions was reached rapidly (< 7 days) and that these data can be used to develop thermodynamic equilibrium constants. The solubility data were interpreted using the Pitzer ion–interaction model. The logarithms of the thermodynamic equilibrium constants determined from these data were 1.30 for the dominant reaction at pH < 4.5 [Ca(ISA)2(c) + 2H+ Ca2+ + 2HISA(aq)], and –2.22 for the dominant reaction at 4.5 [Ca(ISA)2(c)+ Ca(ISA)2(aq)]. In addition, the logarithm of the dissociation constant of HISA [HISA(aq) ISA- + H+] was calculated to be –4.46. 相似文献
6.
V. Scheibel C. R. Appoloni H. Schechter 《Journal of Radioanalytical and Nuclear Chemistry》2006,270(1):163-165
Summary Cereal flours are the major component of the Brazilian diet and are also important exportation products. Radioactivity concentrations
of 232 Th, 226Ra, 40K and 137Cs were determined in commercial samples of South-Brazilian cereal flours (soy, wheat, corn, manioc, rye and oat flour) to
verify the radiological security of these foodstuffs. The measurements were carried out by gamma-ray spectrometry using a
66% relative efficiency HPGe detector. The 40K flour activities, at 95% of confidence level were in: soy 474±3 Bq . kg-1; corn 30.0±0.3 Bq . kg-1; rye 94±1 Bq . kg-1; manioc 67±1 Bq . kg-1; oat 76±1 Bq . kg-1 and wheat 36.2±0.4 Bq . kg-1. The lower limit of detection for 40K ranged from 0.54 to 1.43 Bq . kg-1. The 137Cs activities in flour samples were: soy £0.07 Bq . kg-1, corn £0.01 Bq . kg-1, oat £0.03 Bq . kg-1 and in wheat, manioc and rye £0.02 Bq . kg-1. The highest concentrations levels of 232 Th and 226Ra were 0.69±0.04 Bq . kg-1 and 0.44±0.03 Bq . kg-1, respectively, in soy flour. 相似文献
7.
In aqueous acidic media containing an excess of Hbipy+–bipy buffer in the pH 3.5–4.5 range, the complex ion [(bipy)2MnIII(-O)2MnIV(bipy)2]3+
(1) coexists in rapid equilibrium with its diaqua derivative [MnIII,IV
2 (-O)2(bipy)3(H2O)2]3+
(1a) (bipy = 2,2-bipyridine). An excess of N2H5
+ quantitatively reduces the mixture to MnII, itself being oxidised to N2. The first order rate constant, k
o decreases with increasing C
bipy (C
bipy = [Hbipy+] + [bipy]) but increases with increasing [N2H5
+] and [H+]. The observed kinetic dependence can be explained in terms of a reaction between (1a) and N2H5
+. Replacement of solvent H2O with D2O decreases k
o substantially and the effect suggests simultaneous transfer of an electron and a proton in the rate-determining step. The relevance of this observation to the delayed oxidation of H2O in the hydrazine-treated photosystem II is discussed. 相似文献
8.
V. P. Zvolinskii P. I. Zakharov V. K. Shevtsov A. V. Varlamov V. G. Pleshakov G. A. Vasil'ev N. S. Prostakov 《Chemistry of Heterocyclic Compounds》1978,14(2):200-203
The dissociative ionization of 4-azafluorene and its methyl and phenyl derivatives was investigated. The relative intensity of the [M — CH3]+ ion peak depends on the position of the CH3 group in the 4-azafluorene ring. It was established that the loss of an RCN particle (R=H, CH3, and C6H5) for unsubstituted 4-azafluorene takes place from the M+ and [M — H]+ ion, exclusively from the [M — H]+ ion for the methyl-substituted compounds, and from the [M — H]+ and [H — 2H]+ fragments for the phenyl-substituted derivatives. Randomization of the deuterium ions in the 9,9-d2-4-azafluorene molecular ion was observed.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 246–250, February, 1978. 相似文献
9.
Choudhury Utpal Roy Banerjee Saumen Banerjee Rupendranath 《Transition Metal Chemistry》2002,27(1):42-46
In aqueous acid, hydrazine reduces [MnIV
3(-O)4(bipy)4(H2O)2]4+, (1), quantitatively to [MnIII,IV
2(-O)2(bipy)4]3+, (2), and Mn2+ if [N2H+
5] 2 × (stoichiometric amount). At higher [N2H+
5], reduction proceeds up to Mn2+. The reduction of (1) to (2) is strongly catalysed by Mn2+ and the absorbance (A
t
) versus time (t) graphs have sigmoidal shapes. The graphs become steeper with increasing amounts of added Mn2+ and N2H+
5, but remain unchanged when [H+] is changed. The A
t
– t graphs, under various experimental conditions, can all be simulated with a single set of second order rate constants, estimated for the individual steps in a proposed reaction scheme, in which the catalytic action of Mn2+ involves a one-electron and a two-electron reduced form of (1), but not (1) itself. The absence of any proton-dependence of the reaction rate refutes an electroprotic mechanism and an inner-sphere mechanism appears to be most likely for the reduction of (1) by N2H+
5 相似文献
10.
The silver(I) oxide mediated reactions of the gold(III) dichloride complex [{C6H3(CH2
uCl2] 2a with thiosalicylic or salicylic acid gives the respective complexes [{C6H3(CH2
)-2}] 3a (X=S) or 6b (X=O), containing chelating thiosalicylate or salicylate dianion ligands. X-ray studies show that for the thiosalicylate system, the thiosalicylate sulfur atom is trans to the N,N-dimethylamino group, whereas in the structure of the salicylate complex, it is the carboxylate group that is trans to NMe2. Both complexes show puckered metallacycles in the solid state. Electrospray mass spectrometry (ESMS) shows strong [M+H]+ and [2M+H]+ ions for both the gold-thiosalicylate and -salicylate complexes, and these ions possess a high stability towards cone voltage-induced fragmentation. ESMS was also used to identify a minor impurity, the bis(cyclo-aurated) cationic complex [A
Me2)-2-(OMe)-5}2]+ in the starting dihalide complex 2a and in the product 3a. This complex can be formed by reaction of Me4N[AuCl4] with 2 equivalents of the organomercury precursor [Hg{C6H3(CH2NMe2)-2-(OMe)-5}Cl]. The biological (antitumour, antimicrobial and antiviral) activities are also reported, and these reveal the complexes have moderate to high anti-tumour, antibacterial and antifungal activity. 相似文献
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11.
Summary The kinetics of OsO4-catalysed oxidation of cyclopentanol, cyclohexanol and cyclooctanol by alkaline hexacyanoferrate(III) have been studied at low [OH–] so that the equilibrium between alcohol and alkoxide ion is not unduly shifted towards the latter. The reaction shows a first-order dependence in [OH–]. The order of the reaction with respect to cycloalcohol is fractional, indicating the formation of an intermediate complex with OsVIII since the order with respect to hexacyanoferrate(III) ion is zero. The order with respect to OsVIII may be expressed by the equation kobs=a+b[OsVIII]. The analysis of the rate data indicates a significant degree of complex formation between [OsO3(OH)3]– and ROH. It was found that the bimolecular rate constant k for the redox reaction between complex and OH–k1, the forward rate constant for the formation of alkoxide ion. The activation parameters of these rate constants are reported. 相似文献
12.
The trinuclear complex ion [MnIV
3(-O)4(phen)4(H2O)2]4+
(1) is quantitatively reduced by an excess of S2O3
2– to MnII, but the binuclear complex [MnIIIMnIV(-O)2(phen)4]3+, (2) is the only manganese product when [S2O3
2–] = 1.5 [(1)]. With an excess of S2O3
2– biphasic kinetics, (1) k
1
0
(2) k
2
0 MnII is observed, while the reaction with S2O3
2– = 1.5 [(1)], follows one-step second order kinetics with the second order rate constant k = k
0
1/[S2O3
2–]. The rate constant k
0
1 is independent of c
phen ( = [phen] + [Hphen+]) but directly proportional to [H+] and [S2O2–
3]. Rapid formation of an adduct between (1) and S2O2–
3, followed by rate-determining one-electron, one-proton reduction of the adduct, appears logical. A comproportionation reaction in one of the subsequent rapid steps leads to (2) without any MnII co-product. Kinetic dependences for the second step are same to those for an authentic complex of (2), and further support the assigned reaction sequence. 相似文献
13.
An ion-exchange method was used to determine complexation constants for the Ni-oxalate and Ni-carbonate systems in a NaClO4 background electrolyte. The Ni-oxalate data were interpreted in terms of a single Niox(aq) complex having log K
1 values for Ni2+ + ox2– Niox(aq) of 3.9 ± 0.1 (I.S. = 0.5 mol-L–1 p[H] = 7.1) and 4.4 ± 0.1 (I.S. = 0.1 mol-L–1 p[H] = 8.6) at 22 ± 1C. Specific ion-interaction theory (SIT) was used to obtain log K
1
= 5.17 ± 0.05 (95% confidence level and = –0.23 ± 0.15) at I.S. = 0. The Ni-carbonate studies were carried out at p[H] values of 7.5, 8.5, and 9.6 in 0.5 mol-L–1 NaClO4/NaHCO3 solutions. The NiCO3(aq) species was the dominant complex in the [CO3
2–] concentration ranges studied at all three p[H] values. A log K
1 value for Ni2+ + CO3
2– NiCO3(aq) of 2.9 ± 0.3 was deduced at I.S. = 0.5 mol-L–1. Extrapolating this value to zero ionic strength using the SIT approach yielded log K
1
= 4.2 ± 0.3 (95% confidence level and = –0.26 ± 0.04). The data allowed upper bound values for the complexation constants for NiHCO3
+ and Ni(CO3)2
2– to be estimated, i.e., log K
< 1.4 for Ni2+ + HCO3
– NiHCO3
+, and log K
2
< 2 for NiCO3(aq) + CO3
2– Ni(CO3)2
2–, respectively. 相似文献
14.
Ramesh C. Kapoor Raj N. Mehrotra Shared K. Vajpai Purnima Chaudhary 《Transition Metal Chemistry》1991,16(1):65-70
Summary The kinetics of the OsVIII-catalysed oxidation of glycols by alkaline hexacyanoferrate(III) ion exhibits zerothorder dependence in [Fe(CN)
6
3–
] and first-order dependence in [OsO4]. The order with respect to glycols is less than unity, whereas the rate dependence on [OH–] is a combination of two rate constants; one independent of and the other first-order in [OH–]. These observations are commensurate with a mechanism in which two complexes, [OsO4(H2O)G]– and [OsO4(OH)G]2–, are formed either from [OsO4(H2O)(OH)]– or [OsO4(OH)2]2– and the glycol GH, or by [OsO4(H2O)2] and [OsO4(H2O)(OH)]– and the glycolate ion, G–, which is in equilibrium with the glycol GH through the reaction between GH and OH–. Hence there is an ambiguity about the true path for the formation of the two OsVIII-glycol complexes. A reversal in the reactivity order of glycols in the two rate-determining steps, despite the common attack of OH– ion on the two species of OsVIII-complexes, indicates that the two complexes are structurally different because S changes from the negative (corresponding to k11) to positive (related to k2). 相似文献
15.
M. Daňková E. Makrlík P. Vaňura 《Journal of Radioanalytical and Nuclear Chemistry》1997,221(1-2):251-253
From the extraction experiments and -activity measurements, the extraction constant corresponding to the Rb+(aq)+CsL+(nb)RbL+(nb)+Cs+(aq) equilibrium in the two-phase water-nitrobenzene system (L=valinomycin; aq=aqueous phase, nb=nitrobenzene phase) was evaluated in the form logK
ex (Rb+, CsL+)=0.9. Further, the stability constant of the valinomycin-rubidium complex in nitrobenzene saturated with water was calculated as log nb(RbL+)=11.7. 相似文献
16.
From extraction experiments with 133Ba as a tracer, the extraction constant corresponding to the equilibrium Ba2+(aq) + 2A-(aq) + 2L(nb) BaL2
2+(nb) + 2A-(nb) in the two-phase water-nitrobenzene system (A- = picrate, L = benzo-15-crown-5; aq = aqueous phase, nb = nitrobenzene phase) was evaluated as log K
ex (BaL2
2+, 2A-) = 5.7. Furthermore, the stability constant of the benzo-15-crown-5 - barium complex in nitrobenzene saturated with water was calculated: log bnb (BaL2
2+) = 14.6. 相似文献
17.
A. Mutalib T. Sekine T. Omori K. Yoshihara 《Journal of Radioanalytical and Nuclear Chemistry》1994,178(2):311-318
A new convenient method has been proposed to synthesize mixed-ligand -diketonato Tc(III) complexes, using the ligand exchange reaction [Tc(acac)2(CH3CN)2]++L–[Tc(acac)2L]+ +2CH3CN where L is bza, dpm or dbm. The yield was about 30–40%. UV-visible and IR spectra of these complexes were measured. Characteristic features of the compounds were compared with those of the corresponding complexes of ruthenium. 相似文献
18.
E. Makrlík P. Vaňura M. Daňková 《Journal of Radioanalytical and Nuclear Chemistry》1999,242(1):185-187
From extraction experiments and γ-activity measurements, the extraction constant corresponding to the equilibrium 2Li+(aq)+SrL2
2+(nb) 2LiL+(nb)+Sr2+(aq) taking place in the two-phase water-nitrobenzene system (L=15-crown-5; aq=aqueous phase, nb=nitrobenzene phase) was evaluated
as logK
ex
(2Li+;SrL2
2+)=−3.7. Further, the stability constant of the 15-crown-5—lithium complex in nitrobenzene saturated with water was calculated:
log βnh(LiL+)=7.0. 相似文献
19.
Dr. Matthias Tombers Jun. Prof. Dr. Jennifer Meyer Dr. Jonathan Meyer Dr. Arkadiusz Lawicki Dr. Vicente Zamudio-Bayer Dr. Konstantin Hirsch Prof. Dr. J. Tobias Lau Prof. Dr. Bernd von Issendorff Prof. Dr. Akira Terasaki Prof. Dr. Thomas A. Schlathölter Prof. Dr. Ronnie A. Hoekstra Dr. Sebastian Schmidt Prof. Dr. Annie K. Powell Dr. Eva Kessler Dr. Marc H. Prosenc Prof. Dr. Christoph van Wüllen Prof. Dr. Dr. Gereon Niedner-Schatteburg 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(2):e202102592
The phenomenon of single molecule magnet (SMM) behavior of mixed valent Mn12 coordination clusters of general formula [MnIII8MnIV4O12(RCOO)16(H2O)4] had been exemplified by bulk samples of the archetypal [MnIII8MnIV4O12(CH3COO)16(H2O)4] (4) molecule, and the molecular origin of the observed magnetic behavior has found support from extensive studies on the Mn12 system within crystalline material or on molecules attached to a variety of surfaces. Here we report the magnetic signature of the isolated cationic species [Mn12O12(CH3COO)15(CH3CN)]+ (1) by gas phase X-ray Magnetic Circular Dichroism (XMCD) spectroscopy, and we find it closely resembling that of the corresponding bulk samples. Furthermore, we report broken symmetry DFT calculations of spin densities and single ion tensors of the isolated, optimized complexes [Mn12O12(CH3COO)15(CH3CN)]+ (1) , [Mn12O12(CH3COO)16] (2) , [Mn12O12(CH3COO)16(H2O)4] (3) , and the complex in bulk geometry [MnIII8MnIV4O12(CH3COO)16(H2O)4] (5) . The found magnetic fingerprints – experiment and theory alike – are of a remarkable robustness: The MnIV4 core bears almost no magnetic anisotropy while the surrounding MnIII8 ring is highly anisotropic. These signatures are truly intrinsic properties of the Mn12 core scaffold within all of these complexes and largely void of the environment. This likely holds irrespective of bulk packing effects. 相似文献
20.
Tenu R. Gentil S. Baudu S. Counioux J. J. 《Journal of Thermal Analysis and Calorimetry》1999,58(1):89-101
The binary system H2O—UO2(NO3)2 was studied by solubility measurements and constant heat flow thermal analysis. Temperature and composition of the eutectic transformation between ice and uranyl nitrate hexahydrate were accurately defined. A new hydrate with 24 molecules of water decomposes at –21°C according to the peritectoid reaction<UO2(NO3)2·24H2O> <UO2(NO3)2·6H2O> + 18<H2O>The quasi-ideal model was applied to the solid—liquid equilibria, using the following reaction hypothesis:((UO
2
2+
)) + 2((NO
3
–
))+ h((H2O)) ((UO2OH+aq)) + ((H3O+aq + 2((NO
3
–
aq))A complete calculation of the binary system was carried out with a global ionic hydration number h equal to 9 in the aqueous solutions. It allowed to the melting enthalpies of uranyl nitrate hydrates.
This revised version was published online in November 2005 with corrections to the Cover Date. 相似文献