The effect of complex formation upon the redox potentials of metallic ions: Cyclic voltammetry experiments

1988 ◽  
Vol 65 (2) ◽  
pp. 173 ◽  
Author(s):  
Jorge G. Ibanez ◽  
Ignacio Gonzalez ◽  
Marco A. Cardenas
Keyword(s):  
Cyclic Voltammetry ◽  
Complex Formation ◽  
Redox Potentials ◽  
Metallic Ions

The influence of the host–guest interaction on the oxidation of natural flavonoid dyes

2011 ◽  
Vol 76 (12) ◽  
pp. 1651-1667 ◽  
Author(s):  
Šárka Ramešová ◽  
Romana Sokolová ◽  
Ilaria Degano ◽  
Magdaléna Hromadová ◽  
Miroslav Gál ◽  
...  
Keyword(s):  
Cyclic Voltammetry ◽  
Inclusion Complex ◽  
Fluorescence Intensity ◽  
Oxidation Product ◽  
Aqueous Media ◽  
Electrochemical Methods ◽  
Redox Potentials ◽  
Decomposition Products ◽  
Degradation Processes ◽  
Bioorganic Compounds

The influence of the molecular cavity protection on degradation processes of bioorganic compounds quercetin and luteolin used as the original dyes in old tapestries was studied. The degradation processes were studied by electrochemical methods in aqueous media. The products of the exhaustive electrolysis were separated and identified by GC-MS analysis. Cyclic voltammetry characteristics indicate that the inclusion complex is formed. The inclusion affects the redox potentials of both oxidation waves related to the different dissociation forms of the flavonoid molecule. It was shown that decomposition products formed by the oxidation of quercetin are stabilized in the cavity of β-cyclodextrin, including the main oxidation product 2(3′,4′-dihydroxybenzoyl)-2,4,6-trihydroxybenzofuran-3(2H)-one. The formation of the 1:1 inclusion complex of luteolin with β-cyclodextrin is supported by the enhancement of fluorescence intensity. In the case of quercetin, a decrease of fluorescence intensity occurs when 1:1 inclusion complex with β-cyclodextrin is formed.

scholarly journals Redox Properties of 8-Quinolinol and Implications for its Mode of Action

2011 ◽  
Vol 6 (5) ◽  
pp. 1934578X1100600 ◽  
Author(s):  
Vladimir Chobot ◽  
Sigrid Drage ◽  
Franz Hadacek
Keyword(s):  
Antioxidant Activity ◽  
Cyclic Voltammetry ◽  
Complex Formation ◽  
Mode Of Action ◽  
Reactive Oxygen Species Generation ◽  
Reducing Power ◽  
Free Form ◽  
Cytotoxic Activities ◽  
Major Mode ◽  
Deoxyribose Degradation

8-Quinolinol (oxine, 8-hydroxyquinoline) is a simple aromatic alkaloid with allelopathic, antibacterial, antifungal, and cytotoxic activities. Generally, it is assumed that 8-quinolinol toxicity depends on transition metal chelation that negatively affects their availability for metalloenzymes in the cell or reactive oxygen species generation (ROS), which are formed following reduction of molecular oxygen by autoxidation of the redox active metal central atom of the 8-quinolinol complex. On the contrary, beneficial effects of 8-quinolinol and its derivatives in the medication of certain degenerative diseases are known. In this context, the activity of 8-quinolinol derivatives is attributed to their antioxidant activity following iron complex formation. To address this controversial issue, we explore the possible anti- or pro-oxidant effects of 8-quinolinol and its iron complexes in the deoxyribose degradation assay, by cyclic voltammetry and in a biological assay. The antibacterial effects of 8-quinolinol and its complex with iron were evaluated on Curtobacterium flaccumfacies and Paenibacillus amylolyticus. 8-Quinolinol showed strong antioxidant activity in the deoxyribose degradation assay. This activity may not depend exclusively on iron chelation, but probably more on the notable reducing properties of 8-quinolinol; it proved to be a more efficient antioxidant than the flavonoids catechin and quercetin. By contrast, 8-quinolinol showed no pro-oxidative effects in the deoxyribose degradation assay, both in free form and in complex with iron, as it may occur with redox cyclers. Cyclic voltammetry confirmed this too. 8-Quinolinol significantly inhibited bacterial growth and respiration. Idiosyncratically, its 50:1 mixture with iron(III) ions was less active compared with free 8-quinolinol; it even caused a U-shaped nonlinear hormetic effect on growth and failed to inhibit respiration as totally as the pure mixture; the respiration was even accelerated compared with the control as a result of lower stress. Our results support the notion that complex formation with either iron or other transition metals affects the reducing power of 8-quinolinol, but, in contrast to general assumptions, this study finds no support that complex formation with iron represents the major mode of action.

Synthesis, Optical and Electrical Properties of Oligo(phenylenevinylene)s Substituted with Electron-Accepting Sulfonyl Groups

2010 ◽  
Vol 75 ◽  
pp. 103-107 ◽  
Author(s):  
Volker Schmitt ◽  
Stefan Glang ◽  
Heiner Detert
Keyword(s):  
Cyclic Voltammetry ◽  
Optical Properties ◽  
Electrical Properties ◽  
Side Chains ◽  
Optical And Electrical Properties ◽  
Redox Potentials ◽  
Solid Films ◽  
Good Solubility ◽  
Orange Region

Oligo(phenylenevinylene)s (OPV) composed of five rings and electron donating or withdrawing sulfonyl substituents on the central and lateral rings have been investigated. Two strategies were used for the syntheses of the C2-symmetrical OPVs both include PO-activated olefinations as central steps. Six flexible side chains guarantee good solubility in toluene or dichloromethane. In solution and in films stabilised by polystyrene (60%), the chromophores are strongly fluorescent, with emissions in the violet-blue domain from solutions and in the green to orange region from solid films. The redox potentials, determined by cyclic voltammetry, and the optical properties are strongly depending on the position of the acceptor groups.

scholarly journals Complex formation of 5-hydroxyflavone and 5-hydroxyisoflavone with metallic ions and their solvent extraction

1973 ◽  
Vol 22 (2) ◽  
pp. 179-186 ◽  
Author(s):  
Akira MURATA ◽  
Masanori TOMINAGA ◽  
Hisamitsu INOUE ◽  
Tetsuo SUZUKI
Keyword(s):  
Solvent Extraction ◽  
Complex Formation ◽  
Metallic Ions

scholarly journals Spectrophotometric determination of Uranium through complex formation with roxarsone

2020 ◽  
Vol 10 (6) ◽  
pp. 634
Author(s):  
Nashat Mohamed Alanwar Abd alaty
Keyword(s):  
Complex Formation ◽  
Inductively Coupled Plasma ◽  
Rapid Determination ◽  
Molar Absorptivity ◽  
Pure Form ◽  
Metallic Ions ◽  
Font Size ◽  
Uranium Ore ◽  
Inductively Coupled

<p align="left"><span style="font-size: 10pt; font-family: 'Times New Roman', serif;" lang="EN-US">A new sensitive, accurate, and non-extractive spectrophotometric method was developed for the rapid determination of Uranium in pure form and Uranium ore using </span><span style="font-size: 10pt; font-family: 'Times New Roman', serif;" lang="EN-US">roxarsone</span><span style="font-size: 10pt; font-family: 'Times New Roman', serif;" lang="EN-US">. The procedure was based on the complex formation between Uranium (VI) and </span><span style="font-size: 10pt; font-family: 'Times New Roman', serif;" lang="EN-US">roxarsone. This</span><span style="font-size: 10pt; font-family: 'Times New Roman', serif;" lang="EN-US"> showed maximum absorption at </span><span style="font-size: 10pt; font-family: 'Times New Roman', serif;" lang="EN-US">λmax 395 nm</span><span style="font-size: 10pt; font-family: 'Times New Roman', serif;" lang="EN-US"> with a linear relationship in the concentration range from (20-100 µg mLˉ¹) with a molar absorptivity 9.57×10<sup>3</sup>(1mol<sup>-1</sup> cm<sup>-1</sup>). Inductively Coupled Plasma mass spectroscopy (ICP-MS) was used in the study of the interferences caused by some metallic ions, which were effectively masked by tartaric acid and diethylenetriaminepenta-acetic acid (DTPA). </span><span style="font-size: 10pt; font-family: 'Times New Roman', serif;" lang="EN-US">The method holds its accuracy and precision well when applied to the determination of the studied Uranium in its </span><span style="font-size: 10pt; font-family: 'Times New Roman', serif;" lang="EN-US">pure form and Uranium ore</span><span style="font-size: 10pt; font-family: 'Times New Roman', serif;" lang="EN-US">.</span> </p><p class="MsoNormal" style="text-align: center; direction: ltr; unicode-bidi: embed;" align="center"> </p>

Thermodynamic characteristics of NADH/NAD+ analogues in acetonitrile: 2-methyl, 4-methyl and 2,4-dimethyl 1-benzyl-dihydronicotinamides and the corresponding pyridinium species

1995 ◽  
Vol 73 (4) ◽  
pp. 531-538 ◽  
Author(s):  
Agnès Anne ◽  
Jacques Moiroux
Keyword(s):  
Cyclic Voltammetry ◽  
Hydride Transfer ◽  
Thermodynamic Characteristics ◽  
Redox Potentials ◽  
Methyl Substitution ◽  
Cation Radicals ◽  
Reduction Potentials ◽  
Electron Reduction ◽  
Transfer Thermodynamics ◽  
Electron Transfers

Procedures were elaborated for the syntheses of the title compounds. The thermodynamic changes brought about by each methyl substitution were then determined quantitatively. In acetonitrile, the respective one-electron oxidation and one-electron reduction potentials of the NADH and NAD+ analogues were obtained by means of direct and indirect (using ferrocene mediators) cyclic voltammetry. The redox potentials of formal hydride transfers were deduced from the studies of equilibrated reactions occurring between the analogues. The pKa's of the cation radicals ensued. Keywords: NADH/NAD+ methylated analogues, one-electron transfers, hydride transfer, thermodynamics.

Redox Reactions of Bio Molecule for Nano-bio Battery

2006 ◽  
Vol 915 ◽  
Author(s):  
Kwang Min Shin ◽  
Sang Jun Park ◽  
Seong Gil Yoon ◽  
Chang Kee Lee ◽  
Su Ryon Shin ◽  
...  
Keyword(s):  
Cyclic Voltammetry ◽  
Energy Storage ◽  
Metal Oxide ◽  
Redox Reactions ◽  
Methyl Viologen ◽  
Metal Oxide Nanoparticles ◽  
Oxide Nanoparticles ◽  
Redox Potentials ◽  
Inorganic Elements ◽  
Reduction And Oxidation

AbstractMetal oxide nanoparticles within the protein ferritin can act as an energy storage source in nano-bio batteries containing ferrous ferritin and a reconstituted ferritin cage containing different inorganic elements, such as Co, Mn, Ni, and Pt. These components were introduced as two ferritin half-cells with different redox potentials existing between the ferrous ferritin and the reconstituted ferritin. The reduction of ferritin was analyzed in a solution containing 3-[N-morpholino] propanesulfonic acid buffer and oxidized methyl viologen using cyclic voltammetry. The reduction and oxidation peaks of the methyl viologen occurred at potentials of −300 and −100 mV, respectively, and the reduction and the oxidation peaks of the released Fe occurred at potentials of −300 and −100 mV, respectively. The reduction of ferritin was influenced by the pH of the ferritin solution.

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