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1.
Sumita NaskarSubhendu Naskar Heike Mayer-FiggeWilliam S. Sheldrick Shyamal Kumar Chattopadhyay 《Polyhedron》2011,30(3):529-534
Two mononuclear Cu(II) complexes, [Cu(L1H2)](ClO4)1.25Cl0.75·1.25H2O (1) and [Cu(L2H2)](ClO4)2 (2), of the pyridoxal Schiff base ligands N,N′-dipyridoxylethylenediimine (L1H2) and N,N′-dipyridoxyl-1,3-propanediimine (L2H2) are reported. X-ray crystal structures of both complexes are also reported. In both complexes the pyridoxal nitrogen atoms remain protonated. In the solid state, the tetradentate Schiff base ligand is virtually planar in 1, while in 2 the ligand conformation is like an inverted umbrella. In cyclic voltammetry experiments it is found that in these complexes the Cu(III) and Cu(I) states are more easily accessible than in their salen type analogs. The pyridoxal Schiff base complexes are also found to be resistant to oxidative electro-polymerization, unlike their corresponding salicyl aldehyde Schiff base complexes. 相似文献
2.
S. S. Abd El Rehim L. I. Ali N. H. Amin N. F. Mohamed 《Monatshefte für Chemie / Chemical Monthly》1997,128(3):245-254
Summary The electrochemical behaviour of lead in NaOH solution was studied by potentiodynamic and cyclic voltammetric techniques in combination with X-ray diffraction analysis. The active dissolution of lead involves a small shoulderA1 followed by a peakA1 prior to a passive region. The shoulderA1 is assigned to the electroformation of a Pb(OH)2 film, whereas peakA1 is due to the formation of PbO. Beyond the passive region, the current density increases again, forming a small shoulderA2 and a peakA2 prior to the oxygen evolution potential. The shoulderA2 and the peakA2 are correlated to the electrooxidation of PbO to Pb3O4 and PbO2, respectively. The intensity of the anodic peaks increases with increasing alkali concentration, temperature and scan rate. In cyclic voltammetry, the reverse scan shows two cathodic peaksC1 andC2 which are correlated to the electroreduction of PbO and PbO2 respectively, to Pb.
Potentiodynamisches und cyclovoltammetrisches Verhalten einer Bleielektrode in NaOH-Lösung
Zusammenfassung Das elektrochemische Verhalten von Blei in NaOH wurde mittels potentiodynamischer und cyclovoltammetrischer Techniken unter Zuhilfenahme der Röntgenbeugungsanalyse untersucht. Die aktive Auflösung von Blei verläuft über eine SchulterA1, die von einem einer passiven Region vorgelagerten PeakA1 gefolgt wird. Die SchulterA1 wird der elektrochemischen Bildung eines Pb(OH)2-Films, der PeakA1 der Bildung von PbO zugeschrieben. Jenseits der passiven Region steigt die Stromdichte wieder an, und vor Erreichen des Sauerstoffpotentials treten eine kleine SchulterA2 und ein PeakA2 auf, die mit der Elektrooxidation von PbO zu Pb3O4 und PbO2 korrelieren. Analog dazu beobachtet man in der cyclischen Voltammetrie zwei kathodische PeaksC1 undC2, die der Elektroreduktion von PbO und PbO2 zu Pb entsprechen. Die Intensität der anodischen Peaks steigt mit steigender Alkalikonzentration, Temperatur und Scangeschwindigkeit.相似文献
3.
Using (+)-catechin electrodeposited on a carbon-paste electrode as a model system, we have demonstrated the usefulness of
the time-derivative cyclic voltabsorptometry for voltammetric characterization of the deposited films, in the case when not
only the deposited species but also the same ones in free solution participated in redox processes. A long-optical-path thin-layer
cell was used for the voltabsorptometric measurements. The potential-dependent absorption signals were monitored for catechin
at 252 and 279 nm in B-R buffer electrolytes with pH = 1.8. The combination of voltabsorptometry with voltammetry enabled
one measured cyclic voltammogram to become four, which were attributed to catechin and its oxidized state, in free solution
or in deposited state, respectively. The surface coverage of the electrode was evaluated from the cyclic voltammograms obtained
for the deposited catechin, which decreased with the increasing scan rate. Also, the deposited species was found to make a
major contribution to the total voltammetric current, especially at higher scan rates. 相似文献
4.
Summary Using 1,2-naphthoquinone-1-oxime (HL) as the principal ligand, four mixed-ligand ruthenium oximate complexes - namely [Ru(bipy)2(L)]ClO4, [Ru(pap)2(L)]-ClO4, [Ru(bipy)(L)2] and [Ru(PPh3)2(L)2], where bipy = 2,2′-bipyridine and pap = 2-(phenylazo)pyridine- have been synthesized and characterized. In all these complexes,
Ru exists in the +2 state. They are diamagnetic and, in solution, show several intense metal-to-ligand charge transfer (MLCT)
transitions in the vis. region. In MeCN solution, all four complexes show a reversible RuII-RuIII oxidation on the positive side of a standard calomel electrode (s.c.e.), the potential of which varies with the compositions
of the complexes. Reductions of the coordinated co-ligands (bipy or pap) are also observed. 相似文献
5.
Cyclic voltammetry has been employed to investigate the mixed micellar behavior of the binary mixtures of different zwitterionic surfactants such as 3-(N,N-dimethylhexadecylammonio)propane sulfonate (HPS), 3-(N,N-dimethyltetradecylammonio)propane sulfonate (TPS) and 3-(N,N-dimethyldodecylammonio)propane sulfonate (DPS) with three triblock polymers (L64, F127 and P65) by using 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) as an electroactive probe at 25 °C. Critical micellar concentration (cmc) has been determined from the plots of variation in peak current (ip) versus the total concentration of surfactant/triblock polymer. Diffusion coefficient of the electroactive species has also been reported. The regular solution theory approximation has been used to determine various micellar parameters of ideal systems. The variation in micellar mole fraction (X1) of the zwitterionic surfactant supports the formation of mixed micelles, which are rich in triblock polymer component in the surfactant rich region of the mixture and vice versa. The regular solution interaction parameter (β) suggests the formation of mixed micelles due to the synergistic interactions in case of HPS/TPS/DPS + F127/P65 systems and gets affected by EO/PO ratio of triblock polymers. 相似文献
6.
Claudia A. Caro Gerardo Cabello Esteban Landaeta Jerónimo Pérez Miguelina González José H. Zagal 《Journal of Coordination Chemistry》2014,67(23-24):4114-4124
The chitosan–(Fe(II), Co(II), and Cu(II)) complexes were prepared by mixing chitosan (Chi) powder with a salicylaldehyde (Sal, 5-hydrogen (–H)) and their 5-bromo (–Br), 5-chloro (–Cl), 5-methoxy (–OCH3), 5-fluoro (–F), 5-methyl (–CH3), and 5-nitro (–NO2) derivatives (groups R) and mixing these with FeCl2 and CuCl2 in ethanol and with Co(CH3COO)2 solutions in butanol at 80 °C over 8 h in heterogeneous phase, followed by extraction with ethanol and butanol, respectively. The complexes were characterized by FTIR and UV–vis spectroscopy, elemental analysis, and cyclic voltammetry. A linear correlation between the metal formal potential versus the Hammett parameters of the substituents was observed. The electron-withdrawing groups shift the redox potential to positive values, as a result of lowering the energy of the highest occupied molecular orbital. The formal potential was used as a measurement for the driving force of chitosan complexes for redox reactions. 相似文献
7.
S. Biniak M. Pakula A. Światkowski 《Monatshefte für Chemie / Chemical Monthly》1994,125(12):1365-1370
Summary Cyclic voltammetry was used to compare the electrochemical behaviour ofPAN-based carbon fibre electrodes in aqueous (differentpH), acetonitrile and methanol solutions. The sets of fibres used were produced at three temperatures and were oxidized with conc. HNO3 or left nonmodified. The electrode reaction meachanisms probably occurring on the carbon fibre surfaces were analyzed.
Untersuchung thermisch behandelter und oxydierter Kohlefasern mittels zyklischer Voltammetrie in organische und wässrigen Lösungen
Zusammenfassung Es wurde das elektrochemische Verhalten von Kohlefaserelektroden in wassrigen (verschiedenerpH-werl), acetonitrilischen und methanolischen Lösungen verglichen. Die Kohlefasern aufPAN(Polyacrylnitril)-Basis, die sich voneinander in der Temperatur der termischen Behandlung unterscheiden und nicht oder mit konzentrierter Salpetersäure oxidiert wurden, wurden mittels zyklischer Voltammetrie untersucht. Der wahrscheinliche Verlauf der Elektrodeprozesse auf den Kohlefasernoberflächen wurde analysiert.相似文献
8.
9.
This work introduce an easy and fast continuous cyclic voltammetric technique for the propose monitoring of ultra trace amounts of salbutamol in a flow–injection system. The potential waveform, which consisted of the potential steps for cleaning, stripping and potential ramp, was continuously applied on an Au disk microelectrode (with a radius of 12.5 μm). The detection method we propose has some advantages, the greatest of which are: (1) removing oxygen from the analyte solution is no longer necessary, and (2) it is a very fast and appropriate technique for the determination of the drug compound in a wide variety of chromatographic analysis methods. The detection limit for salbutamol was 2.0 × 10−9 M. The relative standard deviation (R.S.D.) of the proposed technique at 10 ng/mL was 3.5% for 10 runs. The effects of pH of eluent, accumulation potential, sweep rate, and accumulation time on the sensitivity of the method for the determination of the salbutamol were investigated. The proposed method was applied to the determination of salbutamol in pharmaceutical preparation and biological samples. 相似文献
10.
François G. Chevallier Alex Goodwin Craig E. Banks Li Jiang Timothy G. J. Jones Richard G. Compton 《Journal of Solid State Electrochemistry》2006,10(10):857-864
An approximate mathematical model for electrochemical dissolution/growth processes of diffusionally independent and well-separated particles randomly dispersed on an inert conducting electrode surface is presented and solved using numerical simulation. The model, mimicking abrasively modified electrodes where particles of electroactive voltammograms solid are immobilised on an electrode surface, provides clear insights into the effects of different parameters on the voltammetric response of such systems and permits the exploration of the competition taking place between mass transport and surface processes. The mathematical model is then compared with experimental data obtained with basal plane pyrolytic graphite electrode abrasively modified with solid particles of perinaphthenone and studied in aqueous solution.Dedicated to Professor Dr. Alan M. Bond on the occasion of his 60th birthday. 相似文献
11.
12.
Using cyclic voltammetric techniques the electrochemical behaviour of gallium in alkali media has been investigated. Three
anodic peaks, one cathodic peak, and a secondary anodic peak—an observation hitherto unreported—are obtained. Detailed analyses
of these various stages of oxidation and reduction based on their peak potential and peak current characteristics have revealed
the nature of the underlying electrochemical reactions. 相似文献
13.
Markus Sailer 《Journal of organometallic chemistry》2006,691(3):299-308
Oligomeric ferrocene-phenothiazine systems, a novel class of organometallic-organic hybrid electrophores, are easily accessible by Suzuki coupling of iodo ferrocenes and phenothiazinyl and diphenothiazinyl pinacolyl boronates. The triad and the pentad with 1,1′-disubstitution on ferrocene adopt preferentially an eclipsed orientation as a consequence of partial intramolecular π-stacking. In cyclic voltammetry the central ferrocenyl unit acts as an electronic communicator between phenothiazinyl side chains. 相似文献
14.
《Journal of Coordination Chemistry》2012,65(6):525-534
Acetamidomalondihydroxamate (K2AcAMDH) and its manganese(II), iron(II), cobalt(II), nickel(II), copper(II) and zinc(II) complexes were synthesized and characterized by elemental analysis, UV–VIS, IR and magnetic susceptibility. The pK a1 and pK a2 values of the dihydroxamic acid in aqueous solution were found to be 8.0?±?0.1 and 9.7?±?0.1. The dihydroxamate anion AcAMDH behaves as a tetradentate bridging ligand through both hydroxamate groups, forming complexes with a metal to ligand ratio of 1?:?1 in the solid state. The FTIR spectra and thermal decompositions of the ligand and its metal complexes were recorded. The redox behavior of the complexes was investigated in aqueous solution by square wave voltammetry and cyclic voltammetry at neutral pH. In contrast to the solid state, in solution the copper(II) and zinc(II) ions form stable complex species with a metal to ligand ratio of 1?:?2. The iron(II) and nickel(II) complexes show a two-electron irreversible reduction behavior, while the copper(II) and zinc(II) complexes undergo reversible electrode reactions. The stability constants of the complexes were determined by square wave voltammetry. 相似文献
15.
Khalid R. Temsamani Taoufik Fahmi Dounia Bouchta Angel E. Kaifer 《Journal of Solid State Electrochemistry》1997,1(2):143-147
Self-assembled monolayers of alkanethiols on gold have been reported to be highly stable for voltammetry experiments in aqueous
electrolyte. In this work a gold electrode has been modified by first depositing one layer of an alkylthiol (S-C18) and then coating by phospholipid multilayers. Voltammetric oxidation of the antipsychotic chlorpromazine at this two-step
modified electrode was followed by means of cyclic voltammetry measurements. The results give important information concerning
the behaviour of the pharmacological agent at the lipid-water interface. Measurements made using the pre-concentration method
allow good sensitivity improvement after 5 min accumulation time. The ability of chlorpromazine to penetrate inside the phospholipid
multilayers has also been investigated under different conditions such as the nature of the phospholipid and the pH of the
medium. The accumulation process seems to be closely related to the charge carried by the phospholipid and by the molecule,
while the incorporation process seems to be independent of the charge carried by the phospholipid and dependent of the degree
of fluidity of their hydrocarbon chains. We found through this work that the acid-base equilibrium of chlorpromazine together
with its amphiphilic properties (as compared with the results of similar studies on phenothiazine) could be responsible for
governing the principal aspects of the drug's behaviour toward biological membranes.
Received: 6 January 1997 / Accepted: 27 February 1997 相似文献
16.
17.
Dalibor Hodko Maria Gamboa-Aldeco Oliver J. Murphy 《Journal of Solid State Electrochemistry》2009,13(7):1063-1075
A photopolymerization process that simultaneously deposits electronically conducting polymer films and incorporates nanophase
silver grains within the films, the silver grains having been formed in situ on irradiating cast, photopolymerizable formulations
containing silver salts, was developed. Polymer films produced from formulations containing large organic anions were very
flexible and strongly adherent to substrates. Polypyrrole films containing silver grains were characterized electronically
on measuring their electronic conductivities and electrochemically on recording their cyclic voltammetric profiles. Conductivities
were affected by the chemical identity and concentration of components added to photopolymerizable formulations. The best
photopolymerized films had a conductivity of the order of 1 S cm−1. Electronically conducting films derived from formulations consisting of a monomer, an electron acceptor/“dopant,” and a
photoinitiator were electrochemically active. They possessed long-term stability under extended electrode potential cycling
conditions, acceptable charge storage capacity, and the ability to oxidize or reduce redox couples in solution.
Paper submitted for inclusion in the special issue of the Journal of Solid State Electrochemistry honouring the 85th birthday
of Professor John O’M. Bockris. 相似文献
18.
Tao Sun Yue li Pan Jie ying Wu Hong ping Zhou Zu zhi Zhao Yu peng Tian 《Transition Metal Chemistry》2007,32(4):449-455
New nonpolymeric diruthenium (II, III) carboxylates of the type [Ru2(μ-O2CR)4Cl] [R = 9-methyl-9H-carbazole, 9-phenyl-9H-carbazole, 9-(4-vinylphenyl)-9H-carbazole] were obtained by reaction of HO2CR with [Ru2(μ-O2CCH3)4Cl] in MeOH–H2O. All complexes were characterized by TG, electron spectroscopy, cyclic voltammetry, and ESR spectra. The solvent influence
on fluorescence was also discussed. Simultaneously, the electrochemical properties of these complexes were discussed in terms
of the most probable electronic configuration of the complexes in solution. The frozen-solution e.s.r. spectra at 110 K give
g = 1.94, 1.99, 1.95 for Ru2(L0)4Cl, Ru2(L1)4Cl and Ru2(L2)4Cl, respectively. The complexes in DMF solution exhibited strong two-photon absorption (t.p.a.) at 532 nm nanosecond laser
pulse. Their t.p.a. coefficient β, t.p.a. cross-section δ have been determined by the Z-scan technique. 相似文献
19.
Mozo JD Carbajo J Sturm JC Núñez-Vergara LJ Moscoso R Squella JA 《Analytica chimica acta》2011,(1):33-43
Cyclic voltammetry (CV) is a very useful electrochemical tool used to study reaction systems that include chemical steps that are coupled to electron transfers. This type of system generally involves the chemical reaction of an electrochemically generated free radical. Published methods exist that are used to determine the kinetics of electrochemically initiated chemical reactions from the measurements of the peak current ratio (ipa/ipc) of a cyclic voltammogram. The published method requires working curves to relate a kinetic parameter to the peak current ratio.In the presented work, a digital simulation package was used to obtain improved working curves for specific working conditions. The curves were compared with the published results for the first- and second-order chemical reactions following the charge transfer step mechanisms.According to the presented results, the previously published working curve is reliable for a mechanism with a first-order chemical reaction; however, a change in the switching potential requires a recalculation of the curve. In the case of mechanisms with a second-order step (dimerisation and disproportionation), several different views exist on how the second-order chemical term should be expressed so that different values of the constant are obtained. Parameters such as electrode type, electrode area, electroactive species concentration, switching potential, scan rate and method for peak current ratio calculation modify the working curves and must always be specified.We propose a standardised method to obtain the most reliable kinetic constant values.The results of this work will permit researchers who handle simulation software to construct their own working curves. Additionally, those who do not have the simulation software could use the working curves described here.The revelations of the presented experiments may be useful to a broad chemistry audience because this study presents a simple and low-cost procedure for the study of free radicals that otherwise should be studied with more sophisticated and expensive techniques, such as ESR or pulse radiolysis. 相似文献
20.
Bing Wei Cai-Xia Lin Li-Li Xie Yao-Feng Yuan 《Journal of organometallic chemistry》2011,696(8):1574-1578
The reaction of α,β-unsaturated ketones of 2,2-diferrocenylpropane with hydrazine led to the formation of 2,2-diferrocenylpropane-substituted dihydropyrazole. The further reaction of dihydropyrazole with p-pyridinecarboxylic acid chloride or benzoyl chloride resulted in the isolation of two novel 2,2-diferrocenylpropane-substituted acyl dihydropyrazole derivatives. All of these compounds were analyzed by MS, IR and 1H NMR spectra. The crystal structure of representative compound, 1-p-pyridine acyl-3-ferrocenyl-5-(2,2-diferrocenylpropane)-4,5-dihydropyrazole (5a) has been elucidated by X-ray diffraction. The electrochemical behaviours of all the compounds have been examined. 相似文献