One-electron reduction of the γ*-isomer of [S2W18O62]4– leads to isolation of the α-isomer

2001 ◽  
Vol 79 (5-6) ◽  
pp. 613-620
Author(s):  
Peter JS Richardt ◽  
Jonathon M White ◽  
Peter A Tregloan ◽  
Alan M Bond ◽  
Anthony G Wedd
Keyword(s):  
Cyclic Voltammetry ◽  
Cyclic Voltammetric ◽  
Space Group ◽  
Redox States ◽  
Scan Rate ◽  
Electron Reduction

Bu4N+ salts of [S2W18O62]5– and [S2W18O62]6– can be isolated by electro reduction of γ*-(Bu4N)4[S2W18O62] in MeCN. α-(Bu4N)5[S2W18O62]·4MeCN crystallizes in space group C2/c with a = 26.226(2) Å, b = 15.570(2) Å, c = 38.407(2) Å, β = 115.59(2)°, V = 14 145(2) Å3, and Z = 8. The observations indicate that a γ* « α isomerization is associated with the [S2W18O62]4–– [S2W18O62]5– couple. However, the transformation could not be detected on the timescale of cyclic voltammetry up to a scan rate of 10 V s–1. The available data suggest that either: (i) the γ* « α equilibrium favors one of the isomers in solution for both redox states, or (ii) the isomerization is slow on the cyclic voltammetric timescale but the differences in E1/2 values for the α-[S2W18O62]4––[S2W18O62]5– and γ*-[S2W18O62]4––[S2W18O62]5– couples cannot be resolved by cyclic voltammetry.Key words: polyoxometalates, synthesis, electrochemistry, isomerization.

Selenium(IV) Electrochemistry on Silver: A Combined Electrochemical Quartz-Crystal Microbalance and Cyclic Voltammetric Investigation

2003 ◽  
Vol 68 (9) ◽  
pp. 1579-1595 ◽  
Author(s):  
Giovanni Pezzatini ◽  
Francesca Loglio ◽  
Massimo Innocenti ◽  
Maria Luisa Foresti
Keyword(s):  
Cyclic Voltammetry ◽  
Quartz Crystal Microbalance ◽  
Electrochemical Behavior ◽  
Quartz Crystal ◽  
Reduction Process ◽  
Electrochemical Quartz Crystal Microbalance ◽  
Potential Range ◽  
Cyclic Voltammetric ◽  
Scan Rate ◽  
Process Of Se

The electrochemical behavior of Se(IV) on silver was investigated by cyclic voltammetry and electrochemical quartz-crystal microbalance (EQCM) measurements. As already reported in the literature, Se(IV) electrochemistry is always complex, and on silver even more, due to the formation of a compound. Our results confirm that the reduction process of Se(IV) occurs through two reaction paths, Se(IV) → Se(0) and Se(IV) → Se(-II); the product Se(-II) then reacts with Se(IV) through a comproportionation reaction. The latter step leads to red Se that, according to the literature, is the only electroactive form of Se(0). The presence of the electroactive red Se is evident both in the negative range of potentials, through the reduction Se(0) → Se(-II), and in the less negative range of potentials, through the oxidation Se(0) → Se(IV). Moreover, our measurements pointed to the formation of a deposit that never redissolves. This deposit seems to be the electroinactive gray Se. The electrochemical behavior of Se(IV) was investigated in the whole potential range accessible on silver. Our results confirm the occurrence of competitive processes whose predominance depends on the scan rate, as well as on the potential limits of voltammetry. A detailed table with the processes occurring in different potential ranges was drawn up.

The Reactions of Electrogenerated [Ni(sacsac)2]-: Biomimetic Chemistry Related to Nickel Enzymes

1995 ◽  
Vol 48 (4) ◽  
pp. 835 ◽  
Author(s):  
PA Lay ◽  
AF Masters ◽  
CD Wasiowych
Keyword(s):  
Cyclic Voltammetry ◽  
Lewis Base ◽  
Spectroscopic Methods ◽  
Initial Product ◽  
Light Water ◽  
Nickel Enzymes ◽  
Controlled Potential Electrolysis ◽  
Scan Rate ◽  
Controlled Potential ◽  
Electron Reduction

The electrochemical reduction of [Ni( sacsac )2] ( sacsac = C5H7S2- = pentane-2,4-dithionate) has been investigated by cyclic voltammetry and controlled-potential electrolysis in acetone/tetra- butylammonium tetrafluoroborate (0.1 M). The reactions of the reduction product(s) with CO, CO2, CH3I, C12H25SH, light and water have been surveyed. At a scan rate of 100 mV s-1, [Ni( sacsac )2] (0.5 mM ) undergoes a quasi-reversible one-electron reduction (∆ Ep = 88 mV) at -1.543 V (v. Fc+/0) and an irreversible four-electron oxidation at +0.635 V. The oxidation generates the 3,5-dimethyl-1,2-dithiolium cation, as evidenced by the observation of the (known) reduction of this cation at -0.840 V. The initial product of the reduction of [Ni( sacsac )2] is a Lewis base, and reacts with light, water, CO, CO2, CH3I and C12H25SH. These reactions have been followed by electrochemical and spectroscopic methods. They appear to be biomimetic for a number of reactions observed for nickel enzymes.

Towards supported catalyst models: the synthesis, characterization, redox chemistry, and structures of the complexes Ti(OAr′)4 (Ar′ = C6H4(2-t-Bu), C6H(2,3,5,6-Me)4)

1991 ◽  
Vol 69 (1) ◽  
pp. 172-178 ◽  
Author(s):  
Robert T. Toth ◽  
Douglas W. Stephan
Keyword(s):  
Chemical Reduction ◽  
Supported Catalyst ◽  
Redox Chemistry ◽  
Orthorhombic Space Group ◽  
Cyclic Voltammetric ◽  
Space Group ◽  
Electron Reduction ◽  
Catalyst Systems ◽  
Ligand Transfer ◽  
Early Late

Reaction of substituted phenoxides with TiCl4 affords the species Ti(OAr′)4 (Ar′ = C6H4(2-t-Bu), 1; Ar′ = C6H(2,3,5,6-Me)4, 2). The compound Ti(OC6H4(2-t-Bu))4, 1, crystallizes in the tetragonal space group [Formula: see text], with a = 15.203(4) Å, c = 8.026(3) Å, Z = 2, and V = 1855(2) Å3. The compound Ti(OC6H(2,3,5,6-Me)4)4, 2, crystallizes in the orthorhombic space group Pbcn, with a = 16.539(7) Å, b = 16.136(6) Å, c = 27.716(12) Å, Z = 8, and V = 7397(9) Å3. The geometry of the Ti coordination sphere in these complexes is best described as pseudo-tetrahedral. In the case of 1 strict crystallographic [Formula: see text] symmetry is imposed. The complex 2 exhibits reversible cyclic voltammetric behaviour consistent with a one electron reduction to the Ti(III) analogue. Chemical reduction of 2 employing sodium amalgam affords the quantitative formation of (C6H(2,3,5,6-Me)4O)2Ti(μ-OC6H(2,3,5,6-Me)4)2Na(THF)2, 3. The reaction of 3 with [(COD)Rh(μ-Cl)]2 does not afford the Ti(III)/Rh(I) early–late heterobimetallic (ELHB) complex (C6H(2,3,5,6-Me)4O)2Ti(μ-OC6H(2,3,5,6-Me)4)2Rh(COD). The nature of all products is not known; however, redox chemistry, in which electron transfer from Ti(III) to Rh(I) occurs is evidenced by the generation of 2 and Rh(0). In addition, ligand transfer reactions giving uncharacterized Rh-alkoxides are suggested by the spectral data. The implications and ramifications for the synthesis of alkoxide bridged ELHB models of bimetallic heterogeneous catalyst systems are discussed. Key words: titanium phenoxides, redox chemistry, structures.

On the theory of cyclic voltammetry for multiple nucleation and growth: Scan rate influence

2021 ◽  
Vol 883 ◽  
pp. 115056
Author(s):  
Alexander V. Kosov ◽  
Olga V. Grishenkova ◽  
Olga L. Semerikova ◽  
Vladimir A. Isaev ◽  
Yurii P. Zaikov
Keyword(s):  
Cyclic Voltammetry ◽  
Nucleation And Growth ◽  
Scan Rate

scholarly journals Surfactant-free synthesis of carbon-supported silver (Ag/C) nanobars as an efficient electrocatalyst for alcohol tolerance and oxidation of sodium borohydride in alkaline medium

2021 ◽  
Vol 3 (6) ◽  
Author(s):  
Santanu Dey ◽  
Pradipta Chakraborty ◽  
Dhiraj Kumar Rana ◽  
Subhamay Pramanik ◽  
Soumen Basu
Keyword(s):  
Cyclic Voltammetry ◽  
Ethylene Glycol ◽  
Alkaline Medium ◽  
Sodium Borohydride ◽  
Metallic Silver ◽  
Alcohol Tolerance ◽  
Current Ratio ◽  
X Ray ◽  
Scan Rate ◽  
Borohydride Oxidation

AbstractWe have synthesized carbon-supported silver (Ag/C) nanobars by a simple surfactant-free hydrothermal method using glucose as the reducing reagent as well as the source of carbon in Ag/C nanobars. Physicochemical characterization of the materials was performed by X-ray Diffraction (XRD), field emission scanning electron microscopy, and energy-dispersive X-ray spectroscopy. The XRD pattern confirmed the presence of a pure metallic silver phase. No carbon phase was detected, which indicates that the carbon exists mainly in the amorphous form. The electrocatalytic activity of Ag/C in different electrolyte solutions such as 0.5 M NaOH, 0.5 M NaOH + 1 M ethanol (EtOH), 0.5 M NaOH + 1 M ethylene glycol (EG), and 0.5 M NaOH + 0.01 M NaBH4 (sodium borohydride) was studied by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and chronoamperometry (CA) study. Alcohol tolerance of the catalysts was also established in the presence of ethanol and ethylene glycol. The forward-to-backward current ratio from cyclic voltammetry (CV) study of Ag/C-20 (20 h) in 0.5 M NaOH + 1 M ethanol solution at 100 mV s−1 scan rate is 4.13 times higher compared to that of Ag/C-5 (5 h). Hence, Ag/C-20 is a better candidate for the tolerance of ethanol. In the presence of ethylene glycol (1 M) in 0.5 M NaOH solution, it is obtained that the forward-to-backward current ratio at the same scan rate for Ag/C-20 is lower than that in the presence of ethanol. The durability of the catalyst was studied by chronoamperometry measurement. We studied the electrochemical kinetics of Ag/C catalysts for borohydride oxidation in an alkaline medium. The basic electrochemical results for borohydride oxidation show that Ag/C has very well strength and activity for direct borohydride oxidation in an alkaline medium. The reaction of borohydride oxidation with the contemporaneous BH4−. hydrolysis was noticed at the oxidized silver surface. Among all the synthesized Ag/C catalysts, Ag/C-20 exhibited the best electrocatalytic performance for borohydride oxidation in an alkaline medium. The activation energy and the number of exchange electrons at Ag/C-20 electrode surface for borohydride electro-oxidation were estimated as 57.2 kJ mol−1 and 2.27, respectively.

Tuning electrochemical and morphological properties of Prussian blue/carbon nanotubes films through scan rate in cyclic voltammetry

2019 ◽  
Vol 338 ◽  
pp. 5-11 ◽  
Author(s):  
Thiago A. Vieira ◽  
Jhonathan R. Souza ◽  
Denise T. Gimenes ◽  
Rodrigo A.A. Munoz ◽  
Edson Nossol
Keyword(s):  
Carbon Nanotubes ◽  
Cyclic Voltammetry ◽  
Prussian Blue ◽  
Blue Carbon ◽  
Morphological Properties ◽  
Scan Rate

scholarly journals NaFePO4 Cathode Prepared from The Caustic Fusion of A Mix Ilmenite-Hematite Followed by Cyclic Voltammetry for Na Insertion

2020 ◽  
Vol 9 (2) ◽  
pp. 142-152
Author(s):  
Fitria Rahmawati ◽  
◽  
Dwi Aman Nur Romadhona ◽  
Syulfi Faiz ◽  
◽  
...  
Keyword(s):  
Electrical Conductivity ◽  
Cyclic Voltammetry ◽  
Secondary Phase ◽  
Impedance Analysis ◽  
Fusion Method ◽  
Peak Point ◽  
Fe Content ◽  
Scan Rate ◽  
Hematite Fe2o3 ◽  
Resistance Value

Research to prepare NaFePO4 cathode material from iron sand was conducted. The iron sand consists of ilmenite FeTiO3 and hematite Fe2O3. A caustic fusion method used to precipitate iron as Fe(OH)3 and it increased Fe content up to 94.71 %. Phosphate precipitation successfully produced trigonal FePO4 and monoclinic FePO4 comply with ICSD#412736 and ICSD#281079. The prepared-FePO4 was then used as a precursor for Na insertion by applying cyclic voltammetry mode within 2.0 – 4.0 V with 0.05 mVs-1 of the scan rate. It produced orthorhombic olivine NaFePO4 and a secondary phase of orthorhombic Na0.7FePO4. Impedance analysis at 20 Hz – 5 MHz found that the material provided a semicircle at 100 Hz peak point, indicating electrode-bulk interface with a resistance value of 1735W, comparable to the electrical conductivity of 5.36 x 10-6 Scm-1. Even though the conductivity value is quite lower than NaFePO4 prepared from a commercial FePO4 that has been conducted in our previous research, however the electrical conductivity still reliable for cathode.

scholarly journals Cobalt(II) complexes with aromatic carboxylates and N-functionalized cyclam bearing 2-pyridylmethyl pendant arms

2005 ◽  
Vol 70 (8-9) ◽  
pp. 1121-1129 ◽  
Author(s):  
Gordana Vuckovic ◽  
V. Stanic ◽  
Sofija Sovilj ◽  
M. Antonijevic-Nikolic ◽  
J. Mrozynski
Keyword(s):  
Cyclic Voltammetry ◽  
Ir Spectroscopy ◽  
Chair Conformation ◽  
Trans Position ◽  
Cyclic Voltammetric ◽  
Aromatic Carboxylates ◽  
Elemental Analyses ◽  
Electrical Conductivities ◽  
Pendant Arms ◽  
Voltammetric Measurements

Novel binuclear Co(II) complexeswithN-functionalized cyclam N,N?,N",N???-tetrakis( 2-pyridylmethyl)tetraazacyclotetradecane (tpmc) and one of the aromatic monoor dicarboxylato ligands (benzoate, phthalate or isophthalate ions) were prepared. They were analyzed and studied by elemental analyses (C, H, N), electrical conductivities, VIS and IR spectroscopy andmagnetic as well as cyclic voltammetric measurements. In [Co2(C6H5COO)2tpmc]ClO4)2.3H2O, the benzoate ligands are most probably coordinated as chelates in the trans-position to each Co(II) and the macrocycle adopts a chair conformation. In the complexes [Co2(Y)tpmc]ClO4)2.zH2O, (Y = phthalate or i-phthalate dianizon, z = 2; 4) it is proposed that the isomeric dicarboxylates are bonded combined as bridges and chelates. The composition and the assumed geometries of the complexes are compared with the, earlier reported, corresponding Cu(II) complexes. Cyclic voltammetry measurements showed that the compounds are electrochemically stable.

Elektrochemische Untersuchungen von BEDT-TTF / Electrochemical Investigations of BEDT-TTF

1989 ◽  
Vol 44 (10) ◽  
pp. 1199-1202 ◽  
Author(s):  
Harald Müller ◽  
Heinz P. Fritz ◽  
Anton Lerf ◽  
Jürgen O. Besenhard
Keyword(s):  
Cyclic Voltammetry ◽  
Significant Influence ◽  
Redox Reactions ◽  
Radical Cations ◽  
Scan Rate ◽  
Influence Of Solvent

The electrochemistry of BEDT-TTF+ was investigated by means of cyclic voltammetry in solvents most frequently used for the electrocrystallization of radical cations of this donor. It can be shown that the reversibility of redox reactions is decreasing with the scan rate, with a significant influence of solvent. The results presented allow conclusions about the mechanism of electrocrystallization.

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