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991.
Refat Abdel-Hamid 《Monatshefte für Chemie / Chemical Monthly》1988,119(4):429-438
The electrochemical reduction of phenolphthalein in dimethylformamide solution containing 0.1 mol dm–3 tetraethylammonium perchlorate at the hanging dropping mercury electrode showed an irreversible two-electron voltammetric peak. It was found that the CV peak is diffusion-controlled at low concentrations (0.4 mmol dm–3). At higher concentration (0.5 mmol dm–3) a postpeak was developed besides the diffusion-controlled one which was assigned to the adsorbed depolarizer. Cyclic voltammetric studies indicate that phenolphthalein follows an ECEC mechanism. Convolution and deconvolution potential sweep voltammetry confirm that mechanism.
Mechanismus der voltametrischen Reduktion von Phenolphthalein an der Quecksilberelektrode inDMF
Zusammenfassung Die elektrochemische Reduktion von Phenolphthalein an der tropfenden Quecksilberelektrode in Dimethylformamidlösung mit einem Gehalt von 0.1 mol dm–3 an Tetraethylammoniumperchlorat zeigte ein irreversibles voltametrisches Maximum für zwei Elektronen. Es zeigte sich, daß der CV-Peak bei niederen Konzentrationen (0.4 mmol dm–3) diffusionskontrolliert ist. Bei höheren Konzentrationen (0.5 mmol dm–3) entwickelte sich ein nachkommendes Maximum neben dem diffusionskontrollierten, welches dem adsorbierten Depolarisator zugeordnet wurde. Untersuchungen mittels cyclischer Voltametrie zeigten, daß Phenolphthalein einem ECEC-Mechanismus folgt. Konvolutions-und Dekonvolutions-Potential-Sweep-Voltametrie bestätigten diesen Mechanismus.相似文献
992.
Copper-nickel bimetallic nanoparticles decorated on carboxylated multi-walled carbon nanotubes (Cu/Ni/CMWCNTs)were prepared by using a simple one-pot solvothermal method,which was then employed to construct a highly sensitive non-enzymatic glucose sensor. The modified electrode showed high sensitivity and stability in glucose detection,which was mainly attributed to the synergistic effect of the compact copper-nickel nanocomposite and carboxylated multi-walled carbon nanotubes that possessing high specific surface area to increase the number of active sites and to improve the electrocatalytic activity of the modified electrode. The phase structure and morphology of the material were characterized by X-ray diffraction and scanning electron microscope; the electrochemical performance of the sensor was studied by cyclic voltammetry and chronoamperometry. The sensor had a sensitivity of 1949.1 μµA·L/(mmol·cm2)for glucose detection in the linear range of 1.0-8000 μµmol/L at a potential of 0.55 V,and the detection limit was 0.2 μµmol/L. The sensor was also applied to measure the concentration of glucose in serum samples. The developed nanocomposites sensor has the potential prospect to monitor blood glucose. © 2023, Youke Publishing Co.,Ltd. All rights reserved. 相似文献
993.
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
994.
The reaction of benzaldehyde with aliphatic glycols was performed over Al-MCM-41 with various Si/Al ratios. The effects of various parameters like temperature, mole ratio, reaction time and catalyst amount on the formation of acetals were optimized. The mesoporous Al-MCM-41 (Si/Al ratio 36, 57, 81 and 108) were synthesized by hydrothermal method. The synthesized catalysts were characterized by X-ray diffraction (XRD), nitrogen adsorption–desorption isotherm (BET), thermo gravimetric-differential thermal analysis (TGA-DTA) and TEM techniques. The acidity of the catalysts was measured by pyridine adsorption followed by FT-IR analysis. TEM analysis showed that the honeycomb-like regular arrangement of hexagonal pores on the molecular sieves. The highly hydrophobic Al-MCM-41 (108) showed higher activity than the other Si/Al ratios. The activity of the catalysts showed the following order Al-MCM-41 (108) > Al-MCM-41 (81) > Al-MCM-41 (57) > Al-MCM-41 (36). The hydrophobicity and nucleophilicity of the glycols highly influences the conversion of benzaldehyde, it followed the order; hexylene glycol (HG) > propylene glycol (PG) > ethylene glycol (EG). The results showed that mole ratio of 1:3 (aldehyde:glycol) gave higher yield than the other mole ratios. 相似文献
995.
The electrooxidation of ring-substituted bromobenzylgermatranes in CH3CN and DMF solutions was studied. By cyclic voltammetry supported by DFT B3LYP/6-311G calculations, donor activity of the nitrogen atom was shown to be substantially reduced because of the dative N → Ge coordination compared to Et3N and (HOCH2CH2)3N. In the electrochemical context, the transmission of electronic effects between the ArCH2 moiety and the reaction center (the lone pair of N pointed inside the atrane cage) is well described by the generalized additive inductive model including mesomeric interactions. The oxidation process follows classical scheme for tertiary amines - reversible electron transfer with the ensuing deprotonation of α-carbon atom; at low scan rates the process is reversible/quasi-reversible and at higher rates it is under electron transfer control. Anodic cyanation of m-bromobenzylgermatrane was performed. 相似文献
996.
《Analytical letters》2012,45(17):1913-1925
Abstract The electrochemical behaviour of the R-nitroso salt in 0.5 M HAc/NaAc at pH 4.7 is studied by cyclic voltammetry. The compound shows a very sharp reduction peak at -0.37 V vs SCE giving the corresponding amine derivative. The height of the peak is shown to be inversely proportional to the iron (II) concentration of the solution. A linear calibration plot is obtained between 0 and 56 ppm of iron (II) using, initially, 4.0 mM solution of the salt. A simple and fast procedure was developed for the analysis of standard samples of ferrous iron. 相似文献
997.
《Journal of Coordination Chemistry》2012,65(19):3172-3179
The reaction of 2-nitro-1,4-benzenedicarboxylic acid (H2nbdc) and 2,2′-bipyridine (2,2′-bipy) with CuCl2 under hydrothermal conditions gives rise to a cyclic dimer [Cu(nbdc)(2,2′-bipy)(H2O)]2 · 2H2O (1). X-ray structural analysis revealed that 1 crystallizes in a monoclinic space group P21/c with a = 7.3801(13) Å, b = 15.305(3) Å, c = 16.333(3) Å, β = 92.951(4)°, V = 1842.5(6) Å3, and Z = 2. Compound 1 represents the first cyclic dimeric example with 1,4-benzenedicarboxylate or its derivatives, in which two carboxylates of the nbdc are nearly perpendicular due to the steric effect by the nitro group. Compound 1 also displays strong fluorescent emission in the solid state. 相似文献
998.
《Journal of Coordination Chemistry》2012,65(23):3846-3859
Salicylaldehyde or 5-bromosalicylaldehyde react with 2,3-diaminophenol to give two unsymmetrical Schiff-bases H2L1, H2L2, respectively. With Fe(III) and Co(II), these ligands lead to four complexes: Fe(III)ClL1, Fe(III)ClL2, Co(II)L1, Co(II)L2. The structures of these complexes were determined by mass spectroscopy, infrared and electronic spectra. Cyclic voltammetry in dimethylformamide (DMF) showed irreversible waves for both ligands. In the same experimental conditions, Fe(III)ClL1 exhibited a reversible redox couple Fe(III)/Fe(II) while the three other complexes showed quasi-reversible systems. The behavior of some of these complexes in the presence of dioxygen and the comparison with cytochrome P450 are described. 相似文献
999.
《Journal of Coordination Chemistry》2012,65(21):3446-3453
A five-coordinate copper(II) complex with the tripod ligand tris(N-methylbenzimidazol-2-ylmethyl)amine (Mentb) and salicylate, with the composition [Cu(Mentb) (salicylate)](ClO4) · 2DMF, was synthesized and characterized by elemental and thermal analyses, electrical conductivity, IR and UV-Vis spectral measurements. The crystal structure of the complex has been determined by single-crystal X-ray diffraction. The Cu(II) is five-coordinate with four N atoms from the Mentb ligand and an O atom of the monodentate salicylate ligand. The N4O donors are in a distorted trigonal-bipyramid geometry. Cyclic voltammograms indicate a quasireversible Cu2+/Cu+ couple. The X-band EPR spectrum of the complex confirms the trigonal-bipyramidal structure with g∥ < g ⊥ and a very small value of A∥ (41 × 10?4 cm?1). 相似文献
1000.
《Journal of Coordination Chemistry》2012,65(20):3517-3530
Electrochemical studies of the newly synthesized bis(triphenyl phosphine) ruthenium(II) complex, cis-[RuCl2(L)(PPh3)2] (1, with L = 2-(2′-pyridyl)quinoxaline, C13N3H9), were performed in acetonitrile (ACN). For this purpose, cyclic voltammograms (CVs) as well as electrochemical impedance spectra (EIS) were recorded on either glassy carbon (GC), platinum (Pt), gold (Au), or multi-walled carbon nanotube (MWCNT) electrodes. Qualitative examination of solutions of 1 in ACN was performed on the basis of conductivity measurements and electrospray ionization mass spectrometry (ESI–MS). The conductivity data suggest that 1 is a 1 : 1 type electrolyte in ACN. The ESI spectra further demonstrate that upon dissolution of 1 in ACN progressive replacement of chloro- and PPh3-ligands by ACN occurs, leading to formation of [RuCl(L)(PPh3)(CH3CN)2]+Cl?, [2 + Cl ? ]. The CVs recorded for [2 + Cl ? ] on various working electrodes demonstrate that the reversibility of the redox couple 22 +/+ enhances with the order: Au < Pt < MWCNT < GC. The EI spectra verify that GC and MWCNT electrodes provide insignificant barrier for interfacial electron transfer since they afford less charge-transfer resistance. 相似文献