共查询到20条相似文献,搜索用时 31 毫秒
1.
The stoichiometries, kinetics and mechanism of the reduction of tetraoxoiodate(VII) ion, IO4
− to the corresponding trioxoiodate(V) ion, IO3
− by n-(2-hydroxylethyl)ethylenediaminetriacetatocobaltate(II) ion, [CoHEDTAOH2]− have been studied in aqueous media at 28 °C, I = 0.50 mol dm−3 (NaClO4) and [H+] = 7.0 × 10−3 mol dm−3. The reaction is first order in [Oxidant] and [Reductant], and the rate is inversely dependent on H+ concentration in the range 5.00 × 10−3 ≤ H+≤ 20.00 × 10−3 mol dm−3 studied. A plot of acid rate constant versus [H+]−1 was linear with intercept. The rate law for the reaction is:
- \frac[ \textCoHEDTAOH2 - ]\textdt = ( a + b[ \textH + ] - 1 )[ \textCoHEDTAOH2 - ][ \textIO4 - ] - {\frac{{\left[ {{\text{CoHEDTAOH}}_{2}^{ - } } \right]}}{{{\text{d}}t}}} = \left( {a + b\left[ {{\text{H}}^{ + } } \right]^{ - 1} } \right)\left[ {{\text{CoHEDTAOH}}_{2}^{ - } } \right]\left[ {{\text{IO}}_{4}^{ - } } \right] 相似文献
2.
Dillip Kumar Baral Sudhanshu Sekhar Rout Jashoda Behera Sudam Chandra Si Prakash Mohanty 《Transition Metal Chemistry》2011,36(2):231-236
The kinetics and mechanism of the substitution reaction between [Cr(H2O)6]3+ and l-Dopa in aqueous medium has been studied over the range 1.8 ≤ pH ≤ 2.6, 1.68 × 10−2 mol dm−3 ≤ [Dopa] ≤ 5.04 × 10−2 mol dm−3, I = 0.1 mol dm−3 (KNO3) at 50 °C. The reaction takes place via an outer sphere association between Cr3+ and l-Dopa followed by chelation. The product was characterized by physicochemical and infrared spectroscopic methods. The antiparkinsonian
activity of the product was found to be higher than that of l-Dopa. 相似文献
3.
The octahedral complex, [CoIII(HL)]·9H2O (H4L = (1,8)-bis(2-hydroxybenzamido)-3,6-diazaoctane) incorporating bis carboxamido-N-, bis
sec-NH, phenolate, and phenol coordination has been synthesized and characterized by analytical, NMR (1H, 13C), e.s.i.-Mass, UV–vis, i.r., and Raman spectroscopy. The formation of the complex has also been confirmed by its single
crystal X-ray structure. The cyclic voltammetry of the sample in DMF ([TEAP] = 0.1 mol dm−3, TEAP = tetraethylammonium perchlorate) displayed irreversible redox processes, [CoIII(HL)] → [CoIV(HL)]+ and [CoIII(HL)] → [CoII(HL)]− at 0.41 and −1.09 V (versus SCE), respectively. A slow and H+ mediated isomerisation was observed for the protonated complex, [CoIII(H2L)]+ (pK = 3.5, 25 °C, I = 0.5 mol dm−3). H2Asc was an efficient reductant for the complex and the reaction involved outer sphere mechanism; the propensity of different
species for intra molecular reduction followed the sequence: [{[CoIII(HL)],(H2Asc)}–H]− <<< {[CoIII(H2L)],(H2Asc)}+ < {[CoIII(HL)],(H2Asc)}. A low value (ca. 3.7 × 10−10 dm3 mol−1 s−1, 25 °C, I = 0.5 mol dm−3) for the self exchange rate constant of the couple [CoIII(HL)]/[CoII(HL)]− indicated that the ligand HL3− with amido (N-) donor offers substantial stability to the CoIII state. HSO3− and [CoIII(HL)] formed an outer sphere complex {[CoIII(HL)],(HSO3−)}, which was slowly transformed to an inner sphere S-bonded sulfito complex, [CoIII(H2L)(HSO3)] and the latter was inert to reduction by external sulfite but underwent intramolecular SIV → CoIII electron transfer very slowly.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
4.
The reductions of [Co(CN)5NO2]3−, [Co(NH3)5NO2]2+ and [Co(NH3)5ONO]2+, by TiIII in aqueous acidic solution have been studied spectrophotometrically. Kinetic studies were carried out using conventional
techniques at an ionic strength of 1.0 mol dm−3 (LiCl/HCl) at 25.0 ± 0.1 °C and acid concentrations between 0.015 and 0.100 mol dm−3. The second-order rate constant is inverse—acid dependent and is described by the limiting rate law:- k2 ≈ k0 + k[H+]−1,where k=k′Ka and Ka is the hydrolytic equilibrium constant for [Ti(H2O)6]3+. Values of k0 obtained for [Co(CN)5NO2]3−, [Co(NH3)5NO2]2+ and [Co(NH3)5ONO]2+ are (1.31 ± 0.05) × 10−2 dm3 mol−1 s−1, (4.53 ± 0.08) × 10−2 dm3 mol−1 s−1 and (1.7 ± 0.08) × 10−2 dm3 mol−1 s−1 respectively, while the corresponding k′ values from reductions by TiOH2+ are 10.27 ± 0.45 dm3 mol−1 s−1, 14.99 ± 0.70 dm3 mol−1 s−1 and 17.93 ± 0.78 dm3 mol−1 s−1 respectively. Values of K
a
obtained for the three complexes lie in the range (1–2) × 10−3 mol dm−3 which suggest an outer-sphere mechanism. 相似文献
5.
Jonathan F. Ojo Jide Ige Grace O. Ogunlusi Olanrewaju Owoyomi Esan S. Olaseni 《Transition Metal Chemistry》2006,31(6):782-785
The kinetics of the reactions between Fe(phen)
3
2+
[phen = tris–(1,10) phenanthroline] and
Co(CN)5X3− (X = Cl, Br or I) have been investigated in aqueous acidic solutions at I = 0.1 mol dm−3 (NaCl/HCl). The reactions were carried out at a fixed acid concentration ([H+] = 0.01 mol dm−3) and the second-order rate constants for the reactions at 25 °C were within the range of (0.151–1.117) dm3 mol−1 s−1. Ion-pair constants K
ip for these reactions, taking into consideration the protonation of the cobalt complexes, were 5.19 × 104, 3.00 × 102 and 4.02 × 104 mol−1 dm−3 for X = Cl, Br and I, respectively. Activation parameters measured for these systems were as follows: ΔH* (kJ K−1 mol−1) = 94.3 ± 0.6, 97.3 ± 1.0 and 109.1 ± 0.4; ΔS* (J K−1) = 69.1 ± 1.9, 74.9 ± 3.2 and 112.3 ± 1.3; ΔG* (kJ) = 73.7 ± 0.6, 75.0 ± 1.0 and 75.7 ± 0.4; E
a
(kJ) = 96.9 ± 0.3, 99.8 ± 0.4, and 122.9 ± 0.3; A (dm3 mol−1 s−1) = (7.079 ± 0.035) × 1016, (1.413 ± 0.011) × 1017, and (9.772 ± 0.027) × 1020 for X = Cl, Br, and I respectively. An outer – sphere mechanism is proposed for all the reactions. 相似文献
6.
Joanna Wiśniewska 《Transition Metal Chemistry》2007,32(6):811-815
The kinetics of the electron-transfer reactions between promazine (ptz) and [Co(en)2(H2O)2]3+ in CF3SO3H solution ([CoIII] = (2–6) × 10−3
m, [ptz] = 2.5 × 10−4
m, [H+] = 0.02 − 0.05 m, I = 0.1 m (H+, K+, CF3SO
3
−
), T = 288–308 K) and [Co(edta)]− in aqueous HCl ([CoIII] = (1 − 4) × 10−3
m, [ptz] = 1 × 10−4
m, [H+] = 0.1 − 0.5 m, I = 1.0 m (H+, Na+, Cl−), T = 313 − 333 K) were studied under the condition of excess CoIII using u.v.–vis. spectroscopy. The reactions produce a CoII species and a stable cationic radical. A linear dependence of the pseudo-first-order rate constant (k
obs) on [CoIII] with a non-zero intercept was established for both redox processes. The rate of reaction with the [Co(en)2(H2O)2]3+ ion was found to be independent of [H+]. In the case of the [Co(edta)]− ion, the k
obs dependence on [H+] was linear and the increasing [H+] accelerates the rate of the outer-sphere electron-transfer reaction. The activation parameters were calculated as follows:
ΔH
≠ = 105 ± 4 kJ mol−1, ΔS
≠ = 93 ± 11 J K−1mol−1 for [Co(en)2(H2O)2]3+; ΔH
≠ = 67 ± 9 kJ mol−1, ΔS
≠ = − 54 ± 28 J K−1mol−1 for [Co(edta)]−. 相似文献
7.
Hasan Marai Ewa Kita Joanna Wojciechowska Paula Wróbel 《Transition Metal Chemistry》2012,37(2):215-223
The following chromium(III) complexes with serine (Ser) and aspartic acid (Asp) were obtained and characterized in solution:
[Cr(ox)2(Aa)]2− (where Aa = Ser or Asp), [Cr(AspH−1)2]− and [Cr(ox)(Ser)2]−. In acidic solutions, [Cr(ox)2(Aa)]2− undergoes acid-catalysed aquation to cis-[Cr(ox)2(H2O)2]− and the appropriate amino acid. [Cr(ox)(Ser)2]− undergoes consecutive acid-catalysed Ser liberation to give [Cr(ox)(H2O)4]+, and the [Cr(Asp)2]− ion is converted into [Cr(Asp)(H2O)4]2+. Kinetics of these reactions were studied under isolation conditions. The determined rate expressions for all the reactions
are of the form: k
obs = a + b[H+]. Reaction mechanisms are proposed, and the meaning of the determined parameters has been established. Evidence for the formation
of an intermediate with O-monodentate amino acid is given. The effect of the R-substituent at the α-carbon atom of the amino
acid on the complex reactivity is discussed. 相似文献
8.
Jonathan F. Ojo Jide Ige Grace O. Ogunlusi Olanrewaju Owoyomi Esan S. Olaseni 《Transition Metal Chemistry》2006,31(3):337-339
The reactions between Fe(Phen)32+[phen = tris-(1,10) phenanthroline] and Co(CN)5X3− (X = Cl, Br or I) have been studied in aqueous acidic solutions at 25 °C and ionic strength in the range I = 0.001–0.02 mol dm−3 (NaCl/HCl). Plots of k2 versus √I, applying Debye–Huckel Theory, gave the values −1.79 ± 0.18, −1.65 ± 0.18 and 1.81 ± 0.10 as the product of charges (ZAZB) for the reactions of Fe(Phen)32+ with the chloro-, bromo- and iodo- complexes respectively. ZAZB of ≈ −2 suggests that the charge on these CoIII complexes cannot be −3 but is −1. This suggests the possibility of protonation of these CoIII complexes. Protonation was investigated over the range [H+] = 0.0001 −0.06 mol dm−3 and the protonation constants Ka obtained are 1.22 × 103, 7.31 × 103 and 9.90 × 102 dm6 mol−3 for X = Cl, Br and I, respectively. 相似文献
9.
The kinetics of the aquation of (H2O)5Cr(O2CCCl3)2+ have been examined at 35–55°C and 1.00M ionic strength with [H+] = 0.01?1.00M. The reaction follows the rate equation -d ln [Crtotal]/dt = (a[H+]?1 + b + c[H+])/(1 + d[H+]), where [Crtotal] is the stoichiometric concentration of the complex. At 45°C a = (1.41 ± 0.03) × 10?7M/s, b = (1.66 ± 0.02) × 10?5 s?1, c = (7.0 ± 0.8) × 10?5M?1·S?1 and d = 2.3 ± 0.3M?1. Two mechanisms consistent with this rate law are discussed, with evidence being presented in favor of an ester hydrolysis mechanism involving steady-state intermediates. Equilibrium and activation parameters were determined. 相似文献
10.
The differential pulse (dp) polarograms of thiamine in neutral aqueous solutions exhibited six peaks at low depolarizer concentration
(⋦10−4 mol dm−3) and only three peaks at concentrations ≥10−3 mol dm−3. Only one of these was found to correspond to the diffusion-controlled reduction of this compound at the dme and this was
shown to be an irreversible two-electron process. The kinetic parameters derived from the dp polarograms were found to be
in good agreement with those calculated from classical polarograms and were:E
1/2=−1·261 Vvs SCE,an
a=0·54 andD≈3·5×10−6 cm2 sec−1 for 10−3 mol dm−3 thiamine in 0·1 mol dm−3 acetate buffer (pH 6·5). The reduction product has been identified as dihydrothiamine. The effect of pH on the dpp of thiamine
was studied in the pH range 0–7. In the pH region 5·5 to 7·0 only one peak attributable to the B1
+ form of thiamine is present. In the pH region 3·5–5·5 another dpp peak attributable to the protonated form (B1H2+) of thiamine was also observed. At pHs less than 3 only one peak was observed which could be attributed to the doubly protonated
form (B1 H2
3+) of thiamine. Surfactants like triton-X-100 and CTABr were found to inhibit the electroreduction of thiamine due to the strong
adsorption of these compounds on the dme. Thiamine itself was found to have an inhibitory effect on its own electroreduction,
although to a smaller extent. 相似文献
11.
The polyoxyethylene chain of non-ionic surfactant Triton X-100 [4-(1,1,3,3-tetramethylbutyl) phenyl polyethylene glycol,TX-100] was degraded by permanganate in the presence of HClO4. The oxidative degradation rate and cloud point have been obtained as a function of [surfactant], [permanganate], [HClO4], and temperature. Dependence of the reaction rate on adding inorganic salts (Na4P2O7, NaF and MnCl2) was also examined. The oxidation rate increased with increase in [TX-100] and [H+]. The higher order kinetics with respect to [TX-100] at lower [H+] shifted to lower order at higher [H+]. The cloud point of TX-100 (67°C) shifted to lower temperature (23±0.5°C) after oxidative degradation of the polyoxyethylene chain. Evidence of complex formation between TX-100 and MnO
4
−
was obtained spectrophotometrically. Presence of the primary alcoholic (–OH) group in the TX-100 skeleton is responsible for the degradation of oxyethylene chain. Both monomeric and aggregated TX-100 molecules are oxidized by permanganate. A catalytic oxidation mechanism is proposed on the basis of the experimental findings. 相似文献
12.
I. A. Charushnikova A. M. Fedoseev N. A. Budantseva I. N. Polyakova Ph. Moisy 《Russian Journal of Coordination Chemistry》2007,33(1):61-67
Uranyl complexes with acetylenedicarboxylic acid, K(H5O2)[UO2L2H2O] · 2H2O (I) and Cs2[UO2L2H2O] · 2H2O (II), L2− = C4O
4
2−
were prepared for the first time. The composition and structure of the complexes were determined by X-ray diffraction. The
crystal data are as follows: a = 16.254(12) ?, b = 13.508(8) ?, c = 7.683(6) ?, β = 90.91(7)°, space group C2/c, V = 1687(2) ?3 (I); a = 7.0745(10), b = 18.4246(10), c = 13.1383(10) ?, space group Abm2, V = 1712.5(3) ?3 (II). The structures of I and II are based on [UO2L2H2O]
n
2−
anionic chains stretched along the [101] direction (I) or [010] direction (II). In I and II, the uranium coordination polyhedron is a pentagonal bipyramid in which the equatorial environment of the uranyl ions is
formed by the oxygen atoms of the four L2− anions and the water molecule. The L2− anions in I and II are bidentate bridging ligands connecting two uranium atoms that are next to each other in the anionic chain; their coordination
capacity is equal to 2. In I, the K+ and H5O
2
+
cations are outer-sphere species. The latter form hydrogen bonds combining the anionic chains shifted by translation b with respect to each other. The [UO2L2H2O]
n
2−
chains in I are surrounded by the potassium and oxonium cations; in II, these are combined by hydrogen bonds into anionic layers between which Cs+ cations are arranged. The IR spectrum of compound II was measured and interpreted.
Original Russian Text ? I.A. Charushnikova, A.M. Fedoseev, N.A. Budantseva, I.N. Polyakova, Ph. Moisy, 2007, published in
Koordinatsionnaya Khimiya, 2007, Vol. 33, No. 1, pp. 63–69. 相似文献
13.
The kinetics of the acid hydrolysis of chromatopenta-amminecobalt(III) ion has been studied using a stopped-flow method over
the acidity range 0.01≤[H+]<-1.0 mol dm−3 and 20.0°C<-ϕ<-30.0°C at ionic strengths 0.5 and 1.0 mol dm−3 (LiNO3). These studies reveal that the complex is first protonated and subsequently hydrolysed to the aquapentaammine cobalt(III)
ion. The rate constants for the hydrolysis of the mono and diprotonated species at 25°C are 0.83±0.01 s−1 and (1.60±0.02)×104 mol−1 dm−3 s−1, respectively.
TMC 2664 相似文献
14.
K. Popa R. J. M. Konings T. Wiss H. Leiste 《Journal of Radioanalytical and Nuclear Chemistry》2007,273(3):563-567
BaxMIV
xCe2−2x
(PO4)2 [MIV=Zr, Hf] monazite-like compounds were succesfully synthesized by solid state reaction for x≤0.2 (MIV=Zr) and x≤0.1 (MIV=Hf). The low miscibility of BaMIV(PO4)2 (MIV=Zr, Hf) compounds in CePO4 was explained on the basis of the monoclinic-to-trigonal phase transition that occurs at 733 K in BaZr(PO4)2 and at 798 K in BaHf(PO4)2. The hydrothermal alteration of these compounds was tested using a modified MCC-1 static leaching test in acid (1 mol·dm−3 HCl) and basic (1 mol dm−3 KOH) solutions at 373 K, 473 K and 573 K; both the experimental fluids and the reacted solid specimens were analyzed by different
analytical techniques and the reaction mechanisms were elucidated. All the tested compounds are stable in 1 mol·dm−3 HCl until 573 K. The stability of the monazites in 1 mol·dm−3 KOH is a function of the temperature. 相似文献
15.
S. M. Blagojević S. R. Anić Ž. D. Čupić N. D. Pejić Lj. Z. Kolar-Anić 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2009,83(9):1496-1501
The kinetic investigations of the malonic acid decomposition (8.00 × 10−3 mol dm−3 ≤ [CH2(COOH)2]0 ≤ 4.30 × 10−2 mol dm−3) in the Belousov-Zhabotinsky (BZ) system in the presence of bromate, bromide, sulfuric acid and cerium sulfate, were performed
in the isothermal closed well stirred reactor at different temperatures (25.0°C ≤ T ≤ 45.0°C). The formal kinetics of the overall BZ reaction, and particularly kinetics in characteristic periods of BZ reaction,
based on the analyses of the bromide oscillograms, was accomplished. The evolution as well as the rate constants and the apparent
activation energies of the reactions, which exist in the preoscillatory and oscillatory periods, are also successfully calculated
by numerical simulations. Simulations are based on the model including the Br2O species.
The article is published in the original. 相似文献
16.
Summary The aquation ofcis-[Co(en)2(NH2Et)O2CR]2+ [R=H or Me] is strongly acid-catalysed and the rate and activation parameters for this process are reported. No significant rate difference is observed in the spontaneous aquation path for the complexes. The acetato complex undergoes acid catalysed aquation at a rate comparable to the of the corresponding formato complex, in contrast with the relative basicities of the coordinated formate and acetate. This result is interpreted in terms of relative solvation effects of the initial and transition states of both complexes.The base hydrolysis of both complexes obeys overall second order kinetics in the 0.05[OH–]T 0.35 mol dm–3 range (I=0.5 mol dm–3). The formato complex reacts five times faster than its acetato analogue under comparable conditions, which is fully consistent with the dissociative mode of activation of the amido conjugate base involving Co–O bond heterolysis. A substantially large positive value for the activation entropy supports SN1CB mechanism for base hydrolysis. 相似文献
17.
The kinetics of L-lysine anation of aquachromium(III) ions have been investigated in the acidity range 5.6 ≤ 105[H+] ≤ 31.6 mol dm−. The reaction takes place with outer-sphere association between Cr3+/CrOH2+ and H2L+ (L =+HGCH (+NH3)(CO
2
t-
), G being the side chain) followed by transformation of the outer-into an inner-sphere complex by slow interchange. The results
are discussed in relation to the data of analogous systems and it is concluded that anation of [Cr(H2O)6]3 + follows anI
a
path whereas that of [Cr(H2O)5OH]2 + follows anI
d
path. 相似文献
18.
Summary Two novel charge-transfer (CT) heteropoly complexes, (C8H12N2)5H7PMo12O40
(1) and (C8H12N2)3H3-PMo12O40·5H2O (2), prepared by reacting p-Me2NC6H4NH2 with the four-electron heteropoly blue H7PMo12O40·12H2O and heteropoly acid H3PMo12O40· xH2O, respectively, were characterized by elemental analysis, and u.v., i.r., XPS and e.s.r. spectroscopies. A sizable electron-transfer
interaction occurs within the product molecules and the heteropoly anions retain their Keggin structure. Their third-order
optical non-linearity coefficients were measured using the Z-scan technique at a concentration of 4.68 × 10−6 mol dm−3 for (1) and 2.79 × 10−6 mol dm−3 for (2), with I
0 = 2.38 × 1013 w m−2 and λ = 532nm. The |χ(3)| for (1) is 2.61 × 10−10 esu and |χ(3)| for (2) is 1.05 × 10−10 esu. 相似文献
19.
The interaction of (1,8)bis(2-hydroxybenzamido)3,6-diazaoctane (LH2) with iron(III) in acidic medium resulted in the formation of a mononuclear complex, Fe(LH3)4+ which further yielded, [Fe(LH2)]3+, [Fe(LH)]2+, and [FeL]+ due to protolytic equilibria. The formation of [Fe(LH3)]4+ was investigated under varying [H+]T (0.01–0.10 mol dm−3) and [Fe3+]T (1.00 × 10−3–1.70 × 10−2, [L]T = 1.0 × 10−4 mol dm−3) (I = 0.3 mol dm−3, 10% MeOH + H2O, 25.0 °C). The reaction was reversible and displayed monophasic kinetics; the dominant path involved Fe(OH)(OH2)
5
2+
and LH
4
2+
. The mechanism is essentially a dissociative interchange (I
d) and the dissociation of the aqua ligand from the encounter complex, [Fe(OH2)5OH2+, H4L2+] is rate limiting. The ligand binds iron(III) in a bidentate ([Fe(H3L)]4+), tetradentate ([Fe(H2L)]3+), pentadentate ([Fe(HL)]2+) and hexadentate fashion ([FeL]+) under varying pH conditions. Iron(III) promoted deprotonation of the amide and phenol moieties and chelation driven deprotonation
of the sec-NH
2
+
of the trien spacer unit are in tune with the above proposition. The mixed ligand complexes, [FeIII(LH)(X)] (X = N
3
−
, NCS−, ACO−) are also reversibly formed in solution thus indicating that there is a replaceable aqua ligand in the complex conforming
to its octahedral coordination, [Fe(LH)(OH2)]2+, the bound ligand is protonated at the sec-NH site. Despite the multidentate nature of the ligand the FeIII complexes are prone to reduction by sulfur(IV) and ascorbic acid. The redox reactions of different iron(III) species, FeIII(LHi) which involved ternary complex formation with the reductants have been investigated kinetically as a function of pH, [SIV]T and [ascorbic acid]T. The substantial pK perturbation of the bound ascorbate in [Fe(LH)(HAsc/Asc)]+/0 (ΔpK
{[Fe(LH)(HAsc)] − HAsc − } > 6) is considered to be compelling evidence for chelation of HAsc−/Asc2− leading to hepta coordination of iron(III) in the ascorbate complexes. A novel binuclear complex with composition, [FeIII
2C20N4H35O11 (NO3)] has been synthesized and characterized by i.r., u.v.–vis, e.s.r., e.s.i.-Mass, 57Fe Mossbauer spectroscopy and magnetic moment measurements. The complex was isolated as a mixture of two forms C
1 and C
2 with 75.3 and 24.7%, respectively as computed from Mossbauer data. The isomer shift (δ) (quadrupole splitting, ΔE
Q) are 0.32 mm s−1 (0.75 mm s−1) and 0.19 mm s−1 (0.68 mm s−1) for C
1 and C
2, respectively. The variable temperature magnetic moment measurements (10–300 K) of the sample showed that C
1 is an oxo dimer exhibiting antiferromagnetic interaction between the iron(III) atoms (S
1 = S
2 = 5/2, J = − 120 cm−1) while the dimer C
2 is a high spin species (S
1 = S
2 = 5/2) and exhibits normal paramagnetism obeying the Curie law. The cyclic voltametry response of the sample (DMF, [TEAP]
= 0.1 mol dm−3) displayed quasi-reversible responses at − 0.577 V and − 1.451 V (versus SCE). This is in tune with the fact that the C
2 species reverts rapidly in solution to the relatively more stable oxo-bridged dimer (C
1) which is reduced in two sequential steps: C1 + e− → [FeL]+ + FeII; [FeL]+ + e− → FeIIL, the high labilility of the FeII complex is attributed to the irreversibility. The X-band e.s.r. spectrum of the polycrystalline sample at room temperature
displayed a weak (unresolved) band at g = 4.2 and a strong band at g = 2.0 with hyperfine splitting due to the coordinated nitrogen (I = 1). At 77 K the band at g = 4.2 is intensified while that at g = 2 is broadened to the extent of near disappearance in agreement with the presence of the exchange coupled iron(III) centres.
Electronic supplementary material Electronic supplementary material is available for this article at
and accessible for authorised users.
An erratum to this article is available at . 相似文献
20.
Dhanpat Rai Dean A. Moore Nancy J. Hess Kevin M. Rosso Linfeng Rao Steve M. Heald 《Journal of solution chemistry》2007,36(10):1261-1285
Chromium(III)-carbonate reactions are expected to be important in managing high-level radioactive wastes. Extensive studies
on the solubility of amorphous Cr(III) hydroxide solid in a wide range of pH (3–13) at two different fixed partial pressures
of CO2(g) (0.003 or 0.03 atm.), and as functions of K2CO3 concentrations (0.01 to 5.8 mol⋅kg−1) in the presence of 0.01 mol⋅dm−3 KOH and KHCO3 concentrations (0.001 to 0.826 mol⋅kg−1) at room temperature (22±2 °C) were carried out to obtain reliable thermodynamic data for important Cr(III)-carbonate reactions.
A combination of techniques (XRD, XANES, EXAFS, UV-Vis-NIR spectroscopy, thermodynamic analyses of solubility data, and quantum
mechanical calculations) was used to characterize the solid and aqueous species. The Pitzer ion-interaction approach was used
to interpret the solubility data. Only two aqueous species [Cr(OH)(CO3)22− and Cr(OH)4CO33−] are required to explain Cr(III)-carbonate reactions in a wide range of pH, CO2(g) partial pressures, and bicarbonate and carbonate concentrations. Calculations based on density functional theory support
the existence of these species. The log 10
K° values of reactions involving these species [{Cr(OH)3(am) + 2CO2(g)⇌Cr(OH)(CO3)22−+2H+} and {Cr(OH)3(am) + OH−+CO32−
⇌Cr(OH)4CO33−}] were found to be −(19.07±0.41) and −(4.19±0.19), respectively. No other data on any Cr(III)-carbonato complexes are available
for comparisons. 相似文献
|