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1.
Reena Singh Atanu Banerjee Yee Gordon Kajal Krishna Rajak 《Transition Metal Chemistry》2009,34(6):689-694
Abstract The title complexes and have been synthesized in excellent yields by reacting Co(OAc)2·4H2O with H2L1 and H2L2, respectively, in acetonitrile solution. Here, [L1]2− and [L2]2− are the deprotonated forms of N,N-bis(2-hydroxybenzyl)-N′,N′-dimethylethylenediamine and N,N-bis(2-hydroxybenzyl)-2-picolylamine, respectively. The crystal structures of and were determined by x-ray crystallography. In , each cobalt atom has distorted trigonal bipyramid geometry, while in , each cobalt atom has distorted octahedral geometry. Variable temperature magnetic moment measurements show weak antiferromagnetic
interaction in . The magnetic characterization for is in agreement with the presence of Co(II) and Co(III) centers.
Graphical Abstract The title complexes and have been synthesized in excellent yields by reacting Co(OAc)2·4H2O with dianionic N2O2 coordinating ligands. In complex 1, each cobalt atom has distorted trigonal bipyramid geometry, while in complex 2, each
cobalt atom has distorted octahedral geometry. Variable temperature magnetic moment measurements show weak antiferromagnetic
interaction in complex 1. The magnetic characterization for complex 2 is in agreement with the presence of Co(II) and Co(III)
centers.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
2.
Reinaldo F. Teófilo Helder J. Ceragioli Alfredo C. Peterlevitz Leonardo M. Da Silva Flavio S. Damos Márcia M. C. Ferreira Vitor Baranauskas Lauro T. Kubota 《Journal of Solid State Electrochemistry》2007,11(10):1449-1457
The electrochemical properties of boron-doped diamond (BDD) polycrystalline films grown on tungsten wire substrates using
ethanol as a precursor are described. The results obtained show that the use of ethanol improves the electrochemistry properties
of “as-grown” BDD, as it minimizes the graphitic phase upon the surface of BDD, during the growth process. The BDD electrodes
were characterized by Raman spectroscopy, scanning electronic microscopy, cyclic voltammetry (CV), and electrochemical impedance
spectroscopy (EIS). The boron-doping levels of the films were estimated to be ∼1020 B/cm3. The electrochemical behavior was evaluated using the and redox couples and dopamine. Apparent heterogeneous electro-transfer rate constants were determined for these redox systems using the CV and EIS techniques. values in the range of 0.01–0.1 cm s−1 were observed for the and redox couples, while in the special case of dopamine, a lower value of 10−5 cm s−1 was found. The obtained results showed that the use of CH3CH2OH (ethanol) as a carbon source constitutes a promising alternative for manufacturing BDD electrodes for electroanalytical
applications. 相似文献
3.
Oxidation of 3-(4-methoxyphenoxy)-1,2-propanediol (MPPD) by bis(hydrogenperiodato) argentate(III) complex anion, [Ag(HIO6)2]5− has been studied in aqueous alkaline medium by use of conventional spectrophotometry. The major oxidation product of MPPD
has been identified as 3-(4-methoxyphenoxy)-2-ketone-1-propanol by mass spectrometry. The reaction shows overall second-order
kinetics, being first-order in both [Ag(III)] and [MPPD]. The effects of [OH−] and periodate concentration on the observed second-order rate constants k′ have been analyzed, and accordingly an empirical expression has been deduced:
where [IO4
−]tot denotes the total concentration of periodate and k
a = (0.19 ± 0.04) M−1 s−1, k
b = (10.5 ± 0.3) M−2 s−1, and K
1 = (5.0 ± 0.8) × 10−4 M at 25.0 °C and ionic strength of 0.30 M. Activation parameters associated with k
a and k
b have been calculated. A mechanism is proposed, involving two pre-equilibria, leading to formation of a periodato–Ag(III)–MPPD
complex. In the subsequent rate-determining steps, this complex undergoes inner-sphere electron-transfer from the coordinated
MPPD molecule to the metal center by two paths: one path is independent of OH−, while the other is facilitated by a hydroxide ion. 相似文献
4.
Balesh A. Deganatti Nagaraj P. Shetti Sharanappa T. Nandibewoor 《Transition Metal Chemistry》2009,34(2):143-152
The oxidation of l-valine (l-val) by diperiodatocuprate(III) (DPC) in aqueous alkaline medium at a constant ionic strength of 3.0 × 10−3 mol dm−3 was studied spectrophotometrically at 298 K and follows the rate law;
where K
4, K
5 and K
6 are the equilibrium constants for the different steps involved in the mechanism, k is the rate constant for the slow step of the reaction. The appearance of [l-val] term in both numerator and denominator explains the observed less than unit order in [l-val]. Similarly the appearances of [H3IO6
2−] and [OH−] in the denominator obey the experimental negative less than unit order in [H3IO6
2−] and [OH−], respectively. The oxidation reaction in alkaline medium proceeds via a DPC-l-valine complex, which decomposes slowly in a rate determining step followed by other fast steps to give the products. The
main products were identified by spot test and spectroscopic studies. 相似文献
5.
Summary The oxidation of H2O2 by [W(CN)8]3– has been studied in aqueous media between pH 7.87 and 12.10 using both conventional and stopped-flow spectrophotometry. The reaction proceeds without generation of free radicals. The experimental overall rate law,
, strongly suggests two types of mechanisms. The first pathway, characterized by the pH-dependent rate constant k
s, given by
, involves the formation of [W(CN)8· H2O2]3–, [W(CN)8· H2O2·W(CN)8]6– and [W(CN)8· HO]3– intermediates in rapid pre-equilibria steps, and is followed by a one-electron transfer step involving [W(CN)8·HO]3– (k
a) and its conjugate base [W(CN)8·O]4– (k
b). At 25 °C, I = 0.20 m (NaCl), the rate constant
with H
a
=40±6kJmol–1 and S
a
=–151±22JK–1mol–1; the rate constant
with H
b
=36±1kJmol–1 and S
b
=–136±2JK–1mol–1 at 25 °C, I = 0.20 m (NaCl); the acid dissociation constant of [W(CN)8·HO]3–, K
5
=(5.9±1.7)×10–10
m, with
and
is the first acid dissociation constant of H2O2. The second pathway, with rate constant, k
f, involves the formation of [W(CN)8· HO2]4– and is followed by a formal two-electron redox process with [W(CN)8]3–. The pH-dependent rate constant, k
f, is given by
. The rate constant k
7
=23±6m
–1
s
–1 with
and
at 25°C, I = 0.20 m (NaCl). 相似文献
6.
Li-Hua Bi Sib Sankar Mal Nadeen H. Nsouli Michael H. Dickman Ulrich Kortz Saritha Nellutla Naresh S. Dalal Manuel Prinz Georg Hofmann Manfred Neumann 《Journal of Cluster Science》2008,19(1):259-273
The mixed-valence 24-vanadophosphate
(1) has been synthesized and characterized in the solid state by IR, magnetism, EPR, XPS, and elemental analysis. Single-crystal
X-ray analysis was carried out on (Na-1), which crystallizes in the triclinic system, space group , with a = 17.168(3) ?, b = 18.1971(14) ?, c = 20.1422(13) ?, α = 114.753(3)°, β = 99.390(4)°, γ = 95.124(4)°, and Z = 2. Polyanion 1 has an unusual, open structure composed of 2 RuIIIO6 octahedra, 2 VIVO6 octahedra, 14 VVO5 square-pyramids, 8 VVO4 tetrahedra, and 2 PO4 tetrahedra which are all directly linked via edges and corners. The outer surface of 1 is decorated with six RuII(dmso)3 groups. XPS studies on Na-1 confirm the presence of 2 RuIII and 6 RuII as well as 22 VV and 2 VIV centers. Magnetic susceptibility data on Na-1 show that the VIV–RuIII pairs are coupled antiferromagnetically, with J
1 = −13 K and J
2 ∼ −3 K. We did not detect any peak in our EPR measurements on Na-1, thus supporting the conclusion that Na-1 is diamagnetic in its ground state.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.
In Memoriam Prof. F. A. Cotton 相似文献
7.
The osmium(VIII) catalysed IO4
− oxidation of DMF in aqueous alkaline medium follows the rate law:
相似文献
8.
The oxidation of H2NOH is first-order both in [NH3OH+] and [AuCl4
–]. The rate is increased by the increase in [Cl–] and decreased with increase in [H+]. The stoichiometry ratio, [NH3OH+]/[AuCl4
–], is 1. The mechanism consists of the following reactions.
9.
Yuan Yuan Liu Bin Zhai Hua Cai Bin Ding Xiao-Jun Zhao 《Transition Metal Chemistry》2009,34(6):629-635
Using the tripodal ligand N-(carbamoylmethyl)-iminodiacetatic acid (H2ADA), a two dimensional AgI coordination polymer [Ag(HADA)]
n
(1) and a mononuclear complex [CrIII(ADA)2](H2O)(H3O) (2) have been isolated. Using 2 as a precursor, a novel 3D heterometallic compound (3) was obtained. In 1 the singly deprotonated HADA− ligand adopts a novel asymmetrical η1,η1,η2,μ4-tetradentate coordination mode while in 3 four different coordination modes of ADA2− are observed. The solid-state fluorescence spectrum of 1 shows a maximum at 615 nm whereas no fluorescence emission band was observed for free H2ADA.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
10.
A novel thiocyanate (SCN−)-selective PVC membrane electrode based on a zinc-phthalocyanine (ZnPc) complex as neutral carrier is described. The membrane electrode containing ZnPc with 5.1% (w/w) ionophore, 29.2% (w/w) PVC, and 65.7% (w/w) 2-nitrophenyl octyl ether (o-NPOE) as plasticizer displayed an anti-Hofmeister selectivity sequence , and exhibited near-Nernstian potential response to thiocyanate ranging from about 1.0×10−1 to 1.0×10−6 mol L−1 with a detection limit of 7.5×10−7 mol L−1 and a slope of 58.1±0.5 mV per decade in pH 3.0 phosphate buffer solution at 25 °C. This preferential response is believed to be associated with the unique coordination between the central metal of the carrier and thiocyanate.
相似文献
11.
This work reports on the removal of organic matter and nitrogen in a radial-flow aerobic-anoxic immobilized biomass (RAIB)
reactor fed with domestic sewage pretreated in a horizontal-flow anaerobic immobilized biomass (HAIB) reactor. Polyurethane
foam was used as support material for biomass attachment in both reactors. In batch experiments, a first-order kinetic model
with residual concentration represented the organic matter removal rate, whereas nitrogen conversion followed a pseudo-first-order
reaction in series model, with kinetic constants k
1 (ammonium to nitrite) and k
2 (nitrite to nitrate) of 0.25 and 6.62 h−1, respectively. The RAIB reactor was operated in continuous-flow mode and changes in the airflow rate and hydraulic retention
time were found to interfere in the apparent kinetic constants to the nitritation (k
1) and nitratation (k
2). Nitrification and denitrification were achieved in the partially aerated RAIB reactor operating with hydraulic retention
times of 3.3 h and 2.7 h in the aerobic and anoxic zones, respectively. Ethanol was added in the anoxic zone of the reactor
to promote denitrification. The effluent flow of the RAIB reactor presented a COD of 52 mg l−1, and concentrations of 2 mg , 1.24 mg and 3.46 mg . 相似文献
12.
K. S. Gupta R. K. Mehta A. K. Sharma P. K. Mudgal S. P. Bansal 《Transition Metal Chemistry》2008,33(7):809-817
For getting an insight into the mechanism of atmospheric autoxidation of sulfur(IV), the kinetics of this autoxidation reaction
catalyzed by CoO, Co2O3 and Ni2O3 in buffered alkaline medium has been studied, and found to be defined by Eqs. I and II for catalysis by cobalt oxides and
Ni2O3, respectively.
13.
K. Juodkazis J. Juodkazytė R. Vilkauskaitė V. Jasulaitienė 《Journal of Solid State Electrochemistry》2008,12(11):1469-1479
The processes of nickel surface anodic oxidation taking place within the range of potentials preceding oxygen evolution reaction
(OER) in the solutions of 1 M KOH, 0.5 M K2SO4, and 0.5 M H2SO4 have been analyzed in the present paper. Metallic nickel, thermally oxidized nickel, and black nickel coating were used as
Ni electrodes. The methods of cyclic voltammetry and X-ray photoelectron spectroscopy were employed. The study was undertaken
with a view to find the evidence of peroxide-type nickel surface compounds formation in the course of OER on the Ni electrode
surface. On the basis of experimental results and literature data, it has been suggested that in alkaline solution at E ≈ 1.5 V (RHE) reversible electrochemical formation of Ni(IV) peroxide takes place according to the reaction as follows: This reaction accounts for both the underpotential (with respect to ) formation of O2 from NiOO2 peroxide and also small experimental values of dE/dlgi slope (<60 mV) at low anodic current densities, which are characteristic for the two-electron transfer process. It has been
inferred that the composition of the γ-NiOOH phase, indicated in the Bode and revised Pourbaix diagrams, should be ∼5/6 NiOOH + ∼1/6
NiOO2. The schemes demonstrating potential-dependent transitions between Ni surface oxygen compounds are presented, and the electrocatalytic
mechanisms of OER in alkaline, acid, and neutral medium have been proposed. 相似文献
14.
K. Juodkazis J. Juodkazytė V. Šukienė A. Grigucevičienė A. Selskis 《Journal of Solid State Electrochemistry》2008,12(11):1399-1404
Comparative study of capacitative properties of RuO2/0.5 M H2SO4 and Ru/0.5 M H2SO4 interfaces has been performed with a view to find out the nature of electrochemical processes involved in the charge storage
mechanism of ruthenium (IV) oxide. The methods of cyclic voltammetry and scanning electron microscopy (SEM) were employed
for the investigation of electrochemical behavior and surface morphology of RuO2 electrodes. It has been suggested that supercapacitor behavior of RuO2 phase in the potential E range between 0.4 and 1.4 V vs reference hydrogen electrode (RHE) should be attributed to double-layer-type capacitance,
related to non-faradaic highly reversible process of ionic pair formation and annihilation at RuO2/electrolyte interface as described by following summary equation:
15.
Dubey Sapna Sharma Neetu Khandelwal Chandra L. Sharma Prem D. 《Transition Metal Chemistry》2003,28(2):176-181
The kinetics of osmium(VIII)-catalyzed oxidation of hypophosphite with hexacyanoferrate(III) in alkaline medium has been studied. The rate is independent of the concentration of the oxidant. The order with respect to hydroxide ion is variable. Rate law (1) conforms with the experimental observations.
16.
Toshiyuki Abe Keiji Nagai Takeshi Matsukawa Akio Tajiri Takayoshi Norimatsu 《Journal of Solid State Electrochemistry》2007,11(2):303-309
We have recently reported that the organic bilayer of 3,4,9,10-perylenetetracarboxyl-bisbenzimidazole (PTCBI, n-type semiconductor) and 29H,31H-phthalocyanine (H2Pc, p-type semiconductor), which is a part of a photovoltaic cell, acts as a photoanode in the water phase (Abe et al., ChemPhysChem 5:716, [2004]); in that case, the generation of the photocurrent involving an irreversible thiol oxidation at the H2Pc/water interface took place to be coupled with hole conduction through the H2Pc layer, based on the photophysical character of the bilayer. In the present work, the photoelectrode characteristics of the bilayer were investigated in the water phase containing a redox molecule , where the photo-induced oxidation and reduction for the couple were found to take place at the bilayer. The photoanodic current involving the oxidation efficiently occurred at the interface of H2Pc/water, similar to the previous example. In the view of the voltammograms obtained, it was noted that there are pin-holes in the H2Pc layer of the bilayer, leading to a cathodic reaction with at the PTCBI surface especially in the dark; that is, the band bending at the PTCBI/water interface can essentially be reduced by applying a negative potential [e.g., < ∼ 0 V (vs Ag/AgCl)] to the PTCBI, when the cathodic reaction may take place through the conduction band of the PTCBI. Moreover, under that applied potential condition of irradiation, the photogenerated electron carrier part can move to the PTCBI surface, thus enhancing the reduction of . 相似文献
17.
2-Pivaloylamino-6-acetonyl-isoxanthopterin (1,
) has been reacted with
under suitable conditions for synthesizing the new compound
] (2). It has been characterized by elemental analysis, electrospray ionization mass spectrometry, magnetic susceptibility measurement,
different spectroscopic techniques, and cyclic voltammetry. Molecular mechanics (MM2) method provided with its optimized geometry
(having lowest steric energy), consistent with the above data; the optimized bond lengths and bond angles data tally with
the literature X-ray structural data. Reactivity of (2) towards phenylalanine in the presence of
in methanol has been followed both kinetically and stoichiometrically; a reasonable amount of tyrosine could be recovered
from the reaction medium. The negative
value (−274.0 J mol−1
indicates an associative pathway for this process. (2) is also able to react with bromobenzene as indicated by time-dependent absorption spectra as well as product identification.
Efficacy of the pterin ligand residue
of (2) in rendering the latter reactive towards the above-mentioned organic compounds, has been discussed on the basis of experimental
evidence. 相似文献
18.
The mechanism of the Co(II) catalytic electroreduction of water insoluble CoR2 salt in the presence of cysteine was developed. CoR2 = cobalt(II) cyclohexylbutyrate is the component of a carbon paste electrode. Electrode surface consecutive reactions are:
(a) fast (equilibrium) reaction of the complex formation, (b) rate-determining reversible reaction of the promoting process of CoR(Ac+) complex formation, (c) rate-determining irreversible reaction of the electroactive complex formation with ligand-induced adsorption, and (d) fast irreversible reaction of the electroreduction. Reactions (a,b) connected with CoR2 dissolution and reactions (c,d) connected with CoR2 electroreduction are catalyzed by . Regeneration of (reactions “b,d”) and accumulation of atomic Co(0) (reaction “d”) take place. Experimental data [Sugawara et al., Bioelectrochem
Bioenergetics 26:469, 1991]: i
a vs E (i
a is anodic peak, E is cathodic accumulation potential), i
a vs , and i
a vs pH have been quantitatively explained. 相似文献
19.
The aluminium alloy Al-12Si has been polarized by potentiodynamic method at 25 °C under magnetic stirring and in an aerated
solution. Its electrochemical behaviour was tested first by varying the concentration of NaI or NaCl (10−4, 10−3, 10−2) added respectively to NaCl or NaI (10−3 M), and the pH of NaCl 10−3 M (pH = 2.3, 7.3, 10) when adding HCl or NaOH (i.e. the composition of the solution), then by incorporating different ions
familiar to an industrial atmosphere (Cu2+, Zn2+, , , ) at 10−6 M to NaCl 10−3 M (i.e. the electrolyte nature). The use of the electrokinetic curves obtained allowed the access to the passivation (i
pass
, E
rup
and E
rep
) and to the electrokinetic parameters (i
corr
, R
p
and P). They prove the behaviour dependence of the above alloy on the composition and nature of the electrolyte. 相似文献
20.
The kinetics fo dissociation of thebis complexes [Cu(LH)2]2+ formed by CuII with biguanide andN
1-substituted methyl, phenyl, dimethyl and diethyl biguanides into the mono biguanide complexes in aqueous NaOAc-HOAc buffer media have been studied by stopped-flow spectrophotometry. The results, under pseudo-first-order conditions, indicate kobs=ko+kH[H+]. For the different complexes ko values are comparable, but kH values differ appreciably; log kH
versus log K
d
H
is linear withca. unit slope K
d
H
being the equilibrium constant for the process:
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