Polarographic redox potentials of diazotized polycyclic aromatic amines and the absolute electrode potentials

1984 ◽  
Vol 62 (9) ◽  
pp. 1772-1775 ◽  
Author(s):  
Richard M. Elofson ◽  
Fahmi F. Gadallah ◽  
Karlo F. Schulz ◽  
James K. Laidler
Keyword(s):  
Diazonium Salts ◽  
Redox Potentials ◽  
Midpoint Potential ◽  
Electrode Potentials ◽  
Half Wave ◽  
Solvation Energies ◽  
Polycyclic Aromatic ◽  
Occupied Orbital ◽  
C Nmr ◽  
Vacant Orbital

The half-wave potentials (E1/2) of polycyclic diazonium salts as well as those of the parent hydrocarbons, the corresponding aldehydes, and the nitro compounds, when plotted against the coefficient of the energy of either the lowest vacant orbital −mm−1 or the coefficient of the highest occupied orbital +mm of the parent hydrocarbon tend toward the midpoint potential, Em, equal to −0.31 V vs. sce as established by Parker. The polarographic results are correlated with 13C nmr results with comments on solvation energies.

1,1’-Biaceanthrylene and 2,2'-Biaceanthrylene: Models for Linking Larger Polycyclic Aromatic Hydrocarbons via Five-Membered Rings

2019 ◽  
Author(s):  
Yachu Du ◽  
Kyle Plunkett
Keyword(s):  
Polycyclic Aromatic Hydrocarbons ◽  
Polycyclic Aromatic Hydrocarbon ◽  
Aromatic Hydrocarbon ◽  
Electronic Properties ◽  
Aromatic Hydrocarbons ◽  
Model Systems ◽  
Redox Potentials ◽  
Dimer Model ◽  
Optical And Electronic Properties ◽  
Polycyclic Aromatic

We show that polycyclic aromatic hydrocarbon (PAH) chromophores that are linked between two five-membered rings can access planarized structures with reduced optical gaps and redox potentials. Two aceanthrylene chromophores were connected into dimer model systems with the chromophores either projected outward (2,2’-biaceanthrylene) or inward (1,1’-biaceanthrylene) and the optical and electronic properties were compared. Only the planar 2,2’-biaceanthrylene system showed significant reductions of the optical gaps (1 eV) and redox potentials in relation to the aceanthrylene monomer.<br>

1,1’-Biaceanthrylene and 2,2'-Biaceanthrylene: Models for Linking Larger Polycyclic Aromatic Hydrocarbons via Five-Membered Rings

2019 ◽  
Author(s):  
Yachu Du ◽  
Kyle Plunkett
Keyword(s):  
Polycyclic Aromatic Hydrocarbons ◽  
Polycyclic Aromatic Hydrocarbon ◽  
Aromatic Hydrocarbon ◽  
Electronic Properties ◽  
Aromatic Hydrocarbons ◽  
Model Systems ◽  
Redox Potentials ◽  
Dimer Model ◽  
Optical And Electronic Properties ◽  
Polycyclic Aromatic

We show that polycyclic aromatic hydrocarbon (PAH) chromophores that are linked between two five-membered rings can access planarized structures with reduced optical gaps and redox potentials. Two aceanthrylene chromophores were connected into dimer model systems with the chromophores either projected outward (2,2’-biaceanthrylene) or inward (1,1’-biaceanthrylene) and the optical and electronic properties were compared. Only the planar 2,2’-biaceanthrylene system showed significant reductions of the optical gaps (1 eV) and redox potentials in relation to the aceanthrylene monomer.<br>

Some thermodynamic and kinetic properties of H2SO4–H3PO4–H2O–Fe(III) system

2021 ◽  
pp. 1-9
Author(s):  
Ya.G. Avdeev ◽  
Keyword(s):  
Diffusion Coefficients ◽  
Arrhenius Equation ◽  
Platinum Electrode ◽  
Molar Fraction ◽  
Redox Couple ◽  
Kinetic Properties ◽  
Cyclic Voltammogram ◽  
Electrode Potentials ◽  
Half Wave ◽  
Sulfate Complexes

The values of the electrode potentials of the redox couple Fe(III) / Fe(II) and the half-wave potentials of the reactions Fe3+ + e– = Fe2+ и Fe2+ — e– = Fe3+ on the cyclic voltammogram of a platinum electrode in acid solutions containing Fe(III) salts have been measured to characterize the oxidizing ability of the H2SO4—H3PO4—H2O—Fe(III) system. The values of these experimentally obtained parameters are close. A decrease in the oxidizing ability of H2SO4 and H3PO4 mixtures containing Fe(III) with an increase in the molar fraction of H3PO4 in them occurs due to the formation of Fe(III) complexes with phosphate anions which are inferior to their hydrate and sulfate complexes in the oxidizing ability. The temperature coefficients of the electrode potential (dE / dt) of the redox couple Fe(III) / Fe(II) in the H2SO4—H2O, H2SO4—H3PO4—H2O and H3PO4–H2O systems were determined experimentally. The diffusion coefficients of Fe(III) in the studied solutions were calculated based on the Randles—Shevchik equation. The temperature dependence of the diffusion coefficients of Fe(III) cations is satisfactorily described by the Arrhenius equation. The parameters of this equation are calculated.

scholarly journals Electrochemical, Spectroscopic, and Computational Investigations on Redox Reactions of Selenium Species on Galena Surfaces

Minerals ◽  
2019 ◽  
Vol 9 (7) ◽  
pp. 437 ◽  
Author(s):  
Peter Cook ◽  
YoungJae Kim ◽  
Ke Yuan ◽  
Maria C. Marcano ◽  
Udo Becker
Keyword(s):  
Photoelectron Spectroscopy ◽  
Redox Reactions ◽  
Redox Potentials ◽  
Free Energies ◽  
Cathodic Peak ◽  
Redox Transformation ◽  
Hydrogen Electrode ◽  
Midpoint Potential ◽  
Ph Conditions ◽  
Cv Measurements

Despite previous studies investigating selenium (Se) redox reactions in the presence of semiconducting minerals, Se redox reactions mediated by galena (PbS) are poorly understood. In this study, the redox chemistry of Se on galena is investigated over a range of environmentally relevant Eh and pH conditions (+0.3 to −0.6 V vs. standard hydrogen electrode, SHE; pH 4.6) using a combination of electrochemical, spectroscopic, and computational approaches. Cyclic voltammetry (CV) measurements reveal one anodic/cathodic peak pair at a midpoint potential of +30 mV (vs. SHE) that represents reduction and oxidation between HSeO3− and H2Se/HSe−. Two peak pairs with midpoint potentials of −400 and −520 mV represent the redox transformation from Se(0) to HSe− and H2Se species, respectively. The changes in Gibbs free energies of adsorption of Se species on galena surfaces as a function of Se oxidation state were modeled using quantum-mechanical calculations and the resulting electrochemical peak shifts are (−0.17 eV for HSeO3−/H2Se, −0.07 eV for HSeO3−/HSe−, 0.15 eV for Se(0)/HSe−, and −0.15 eV for Se(0)/H2Se). These shifts explain deviation between Nernstian equilibrium redox potentials and observed midpoint potentials. X-ray photoelectron spectroscopy (XPS) analysis reveals the formation of Se(0) potentials below −100 mV and Se(0) and Se(−II) species at potentials below −400 mV.

scholarly journals Natural Mediators in the Oxidation of Polycyclic Aromatic Hydrocarbons by Laccase Mediator Systems

2000 ◽  
Vol 66 (2) ◽  
pp. 524-528 ◽  
Author(s):  
Christian Johannes ◽  
Andrzej Majcherczyk
Keyword(s):  
Reduced Glutathione ◽  
White Rot Fungi ◽  
White Rot ◽  
Enzymatic Oxidation ◽  
Redox Potentials ◽  
Maximum Value ◽  
Mediator Systems ◽  
Polycyclic Aromatic ◽  
Oxidation Efficiency ◽  
Hydroxybenzyl Alcohol

ABSTRACT The oxidation of polycyclic aromatic compounds was studied in systems consisting of laccase from Trametes versicolor and so-called mediator compounds. The enzymatic oxidation of acenaphthene, acenaphthylene, anthracene, and fluorene was mediated by various laccase substrates (phenols and aromatic amines) or compounds produced and secreted by white rot fungi. The best natural mediators, such as phenol, aniline, 4-hydroxybenzoic acid, and 4-hydroxybenzyl alcohol were as efficient as the previously described synthetic compounds ABTS [2,2′-azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid)] and 1-hydroxybenzotriazole. The oxidation efficiency increased proportionally with the redox potentials of the phenolic mediators up to a maximum value of 0.9 V and decreased thereafter with redox potentials exceeding this value. Natural compounds such as methionine, cysteine, and reduced glutathione, containing sulfhydryl groups, were also active as mediator compounds.

Characterization of an alkylammonium-montmorillonite-phenanthrene intercalation complex by carbon-13 nuclear magnetic resonance spectroscopy

Clay Minerals ◽  
1998 ◽  
Vol 33 (2) ◽  
pp. 221-229 ◽  
Author(s):  
B. K. G. Theng ◽  
R. H. Newman ◽  
J. S. Whitton
Keyword(s):  
Interlayer Space ◽  
Solid Phase ◽  
Basal Spacing ◽  
Resonance Spectroscopy ◽  
Pure Compounds ◽  
Polycyclic Aromatic ◽  
Relaxation Time Constants ◽  
Silicate Layers ◽  
C Nmr

AbstractLow molecular weight polycyclic aromatic hydrocarbons can intercalate from the solid phase into montmorillonite (Mt) saturated with quaternary alkylammonium ions. However, the interaction and relationship between guest and host organic molecules in the interlayer space of the clay are not well understood. We have intercalated phenanthrene into tetradecyltrimethylammonium (TDTMA)-montmorillonite by a solid-solid reaction. The basal spacing of the original TDTMA-Mt complex is close to 1.8 nm, indicating the presence in the interlayer space of a double layer of TDTMA ions with the alkyl (polymethylene) chains lying parallel to the silicate layers, and the carbon zig-zags adopting an all-trans conformation. After intercalation of phenanthrene the basal spacing increases to about 3.4 nm, indicating a change in orientation of the alkyl chains with respect to the silicate layers. 13C-NMR spectroscopy shows that adding phenanthrene to TDTMA-Mt leads to a displacement by -3 ppm of the -(CH2)n- signal for TDTMA. This signal and that for interlayer phenantbrene are also broadened relative to the respective pure compounds. These observations, together with measurements of nuclear spin relaxation time constants, strongly suggest that in the complex with phenanthrene the polymethylene chains of TDTMA extend away from the silicate layers, and no longer assume a rigid all-trans carbon zig-zag conformation. Rather, the TDTMA chains become relatively disordered and intimately mixed with phenanthrene.

scholarly journals Simple and accurate correlation of experimental redox potentials and DFT-calculated HOMO/LUMO energies of polycyclic aromatic hydrocarbons

2012 ◽  
Vol 19 (7) ◽  
pp. 2845-2848 ◽  
Author(s):  
Dalvin D. Méndez-Hernández ◽  
Pilarisetty Tarakeshwar ◽  
Devens Gust ◽  
Thomas A. Moore ◽  
Ana L. Moore ◽  
...  
Keyword(s):  
Polycyclic Aromatic Hydrocarbons ◽  
Aromatic Hydrocarbons ◽  
Redox Potentials ◽  
Polycyclic Aromatic ◽  
Homo Lumo

Über die relative Lage von Energietermen bei einigen photochemisch aktiven organischen Farbstoffen

1968 ◽  
Vol 23 (2) ◽  
pp. 147-152 ◽  
Author(s):  
A. Stanienda
Keyword(s):  
Excited State ◽  
Metal Ions ◽  
Chlorophyll A ◽  
Photochemical Reaction ◽  
Energy Difference ◽  
Redox Potentials ◽  
Pheophytin A ◽  
Reduction Potentials ◽  
Half Wave ◽  
First Excited State

Anodic and cathodic half wave potentials of porphin, tetraazaporphin, Mg (II)-tetraazaporphin, uroporphyrin I and phtalocyanin were measured respectively calculated, and also the reduction potentials of pheophytin a and thioazacarbocyanines. These and the redox potentials of further porphins were compared with some of their photochemical reaction. It was found that the energy difference between the first excited state and ionization in photochemical active porphins are smaller than in less active dyes. An electron from the first excited state of chlorophyll a e. g. is 0,95 eV more easy removed than from phtalocyanin.The influence of metal ions in systems with Η-bonding, e. g. porphins, 8-oxychinolin and proteins will be discussed.

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