Stepwise reduction of samarium cryptates in propylene carbonate: anions and water concentration effects on the redox behavior of the Sm(III)/Sm(II) couple

1988 ◽  
Vol 66 (9) ◽  
pp. 2172-2176 ◽  
Author(s):  
Edouard Laurent Loufouilou ◽  
Jean Paul Gisselbrecht
Keyword(s):  
Redox Potential ◽  
Propylene Carbonate ◽  
Water Concentration ◽  
Oxidation States ◽  
Mixed Complex ◽  
Polarographic Reduction ◽  
Redox Behavior ◽  
Redox Potentials ◽  
Concentration Effects ◽  
Stepwise Reduction

The polarographic reduction of samarium(III) cryptates with cryptands 222, 221, and 22 was investigated in propylene carbonate. The samarium(III) cryptates are reduced in two consecutive steps, the first step was reversible and corresponded to the reduction of the Sm(III) to the Sm(II) cryptate. The Sm(III)/Sm(II) redox potential of the cryptates depended on the anion used in the complex and, in the case of the cryptate with chloride anions, a stable mixed complex was observed in propylene carbonate. The Sm(III)/Sm(II) redox potentials of the cryptates were more cathodic than the redox potential of the uncomplexed Sm(III)/Sm(II) couple, which is typical of a lower stability of the reduced cryptate. Propylene carbonate does not stabilize low oxidation states of lanthanides by cryptation. This is at variance with behavior observed previously in other media like water and methanol. Variations of redox potentials as a function of increasing amounts of water were accounted for by solvent shielding of samarium(III) upon encapsulation in cryptands.

scholarly journals Role of redox-inactive metals in controlling the redox potential of heterometallic manganese–oxido clusters

2021 ◽  
Author(s):  
Keisuke Saito ◽  
Minesato Nakagawa ◽  
Manoj Mandal ◽  
Hiroshi Ishikita
Keyword(s):  
Photosystem Ii ◽  
Redox Potential ◽  
Quantum Chemical Calculations ◽  
Catalytic Reaction ◽  
Quantum Chemical ◽  
Ionic Radius ◽  
Redox Potentials ◽  
Oxygen Evolving ◽  
Highest Occupied Molecular Orbitals

AbstractPhotosystem II (PSII) contains Ca2+, which is essential to the oxygen-evolving activity of the catalytic Mn4CaO5 complex. Replacement of Ca2+ with other redox-inactive metals results in a loss/decrease of oxygen-evolving activity. To investigate the role of Ca2+ in this catalytic reaction, we investigate artificial Mn3[M]O2 clusters redox-inactive metals  [M] ([M]  = Mg2+, Ca2+, Zn2+, Sr2+, and Y3+), which were synthesized by Tsui et al. (Nat Chem 5:293, 2013). The experimentally measured redox potentials (Em) of these clusters are best described by the energy of their highest occupied molecular orbitals. Quantum chemical calculations showed that the valence of metals predominantly affects Em(MnIII/IV), whereas the ionic radius of metals affects Em(MnIII/IV) only slightly.

scholarly journals Detecting Redox Potentials Using Porous Boron Nitride/ATP-DNA Aptamer/Methylene Blue Biosensor to Monitor Microbial Activities

Micromachines ◽  
2022 ◽  
Vol 13 (1) ◽  
pp. 83
Author(s):  
Kai Guo ◽  
Zirui Song ◽  
Gaoxing Wang ◽  
Chengchun Tang
Keyword(s):  
Methylene Blue ◽  
Microbial Community ◽  
Boron Nitride ◽  
Redox Potential ◽  
Microbial Activity ◽  
Potential Change ◽  
Dna Aptamer ◽  
Redox Potentials ◽  
Microplate Reader

Microbial activity has gained attention because of its impact on the environment and the quality of people’s lives. Most of today’s methods, which include genome sequencing and electrochemistry, are costly and difficult to manage. Our group proposed a method using the redox potential change to detect microbial activity, which is rooted in the concept that metabolic activity can change the redox potential of a microbial community. The redox potential change was captured by a biosensor consisting of porous boron nitride, ATP-DNA aptamer, and methylene blue as the fluorophore. This assembly can switch on or off when there is a redox potential change, and this change leads to a fluorescence change that can be examined using a multipurpose microplate reader. The results show that this biosensor can detect microbial community changes when its composition is changed or toxic metals are ingested.

scholarly journals Temperature-induced diurnal redox potential in soil

2021 ◽  
Author(s):  
Kristof Dorau ◽  
Bianca Bohn ◽  
Lutz Weihermüller ◽  
Tim Mansfeldt
Keyword(s):  
Redox Potential ◽  
Temporal Resolution ◽  
High Temporal Resolution ◽  
Redox Potentials ◽  
Soils And Sediments

With the capabilities to measure redox potentials (EH) at a high temporal resolution, scientists have observed diurnal EH that occur in a distinct periodicity in soils and sediments. These patterns...

Synthesis and hydrolysis of gas-phase lanthanide and actinide oxide nitrate complexes: a correspondence to trivalent metal ion redox potentials and ionization energies

2015 ◽  
Vol 17 (15) ◽  
pp. 9942-9950 ◽  
Author(s):  
Ana F. Lucena ◽  
Célia Lourenço ◽  
Maria C. Michelini ◽  
Philip X. Rutkowski ◽  
José M. Carretas ◽  
...  
Keyword(s):  
Gas Phase ◽  
Metal Ion ◽  
Oxidation States ◽  
Redox Potentials ◽  
Trivalent Metal ◽  
Ionization Energies ◽  
Reduction Potentials ◽  
Hydrolysis Of ◽  
Nitrate Complexes

Gas-phase hydrolysis of lanthanide/actinide MO3(NO3)3−ions relates to the stabilities of the MIVoxidation states, which correlate with IV/III solution reduction potentials and 4th ionization energies.

scholarly journals Site-directed mutations in fungal laccase: effect on redox potential, activity and pH profile

1998 ◽  
Vol 334 (1) ◽  
pp. 63-70 ◽  
Author(s):  
Feng XU ◽  
Randy M. BERKA ◽  
Jill A. WAHLEITHNER ◽  
Beth A. NELSON ◽  
Jeffrey R. SHUSTER ◽  
...  
Keyword(s):  
Redox Potential ◽  
Phenol Oxidase ◽  
Ascorbate Oxidase ◽  
Single Mutation ◽  
Redox Potentials ◽  
Wild Type ◽  
Ph Optimum ◽  
Ph Profile ◽  
Potential Activity

A Myceliophthora thermophila laccase and a Rhizoctonia solani laccase were mutated on a pentapeptide segment believed to be near the type-1 Cu site. The mutation L513F in Myceliophthora laccase and the mutation L470F in Rhizoctonia laccase took place at a position corresponding to the type-1 Cu axial methionine (M517) ligand in Zucchini ascorbate oxidase. The triple mutations V509L,S510E,G511A in Myceliophthora laccase and L466V,E467S,A468G in Rhizoctonia laccase involved a sequence segment whose homologue in ascorbate oxidase is flanked by the M517 and a type-1 Cu-ligating histidine (H512). The single mutation did not yield significant changes in the enzymic properties (including any significant increase in the redox potential of the type-1 Cu). In contrast, the triple mutation resulted in several significant changes. In comparison with the wild type, the Rhizoctonia and Myceliophthora laccase triple mutants had a phenol-oxidase activity whose pH optimum shifted 1 unit lower and higher, respectively. Although the redox potentials were not significantly altered, the Km, kcat and fluoride inhibition of the laccases were greatly changed by the mutations. The observed effects are interpreted as possible mutation-induced structural perturbations on the molecular recognition between the reducing substrate and laccase and on the electron transfer from the substrate to the type-1 Cu centre.

scholarly journals Contributions of Microbial “Contact Leaching” to Pyrite Oxidation under Different Controlled Redox Potentials

Minerals ◽  
2020 ◽  
Vol 10 (10) ◽  
pp. 856
Author(s):  
Bingxu Dong ◽  
Yan Jia ◽  
Qiaoyi Tan ◽  
Heyun Sun ◽  
Renman Ruan
Keyword(s):  
Redox Potential ◽  
Dissolution Rate ◽  
Elemental Sulfur ◽  
Microbial Consortium ◽  
Pyrite Oxidation ◽  
Microbial Consortia ◽  
Redox Potentials ◽  
Sulfur Passivation ◽  
Sulfur Oxidizing ◽  
Contact Oxidation

The function of microbial contact leaching to pyrite oxidation was investigated by analyzing the differences of residue morphologies, leaching rates, surface products, and microbial consortia under different conditions in this study. This was achieved by novel equipment that can control the redox potential of the solution and isolate pyrite from microbial contact oxidation. The morphology of residues showed that the corrosions were a little bit severer in the presence of attached microbes under 750 mV and 850 mV (vs. SHE). At 650 mV, the oxidation of pyrite was undetectable even in the presence of attached microbes. The pyrite dissolution rate was higher with attached microbes than that without attached microbes at 750 mV and 850 mV. The elemental sulfur on the surface of pyrite residues with sessile microorganisms was much less than that without attached microbes at 750 mV and 850 mV, showing that sessile acidophiles may accelerate pyrite leaching by reducing the elemental sulfur inhibition. Many more sulfur-oxidizers were found in the sessile microbial consortium which also supported the idea. The results suggest that the microbial “contact leaching” to pyrite oxidation is limited and relies on the elimination of elemental sulfur passivation by attached sulfur-oxidizing microbes rather than the contact oxidation by EPS-Fe.

scholarly journals The redox potentials of the two-iron plant algal ferredoxins. An electrostatic model

1973 ◽  
Vol 133 (2) ◽  
pp. 283-287 ◽  
Author(s):  
R. J. Kassner ◽  
W. Yang
Keyword(s):  
Electron Transfer ◽  
Free Energy ◽  
Redox Potential ◽  
Negative Charge ◽  
Electrostatic Model ◽  
Redox Potentials ◽  
Electron Transfer Proteins ◽  
Electrostatic Free Energy ◽  
The One ◽  
Charged Ions

The two-iron–sulphur co-ordination centre in plant and algal ferredoxins is considered as a collection of charged ions whose net negative charge is twice that of the one-iron–sulphur protein rubredoxin. Calculation of the electrostatic free-energy changes for reduction of the two types of proteins indicates that the redox potential of the two-iron–sulphur proteins should be more negative than that of the one-iron–sulphur protein and that in biological systems the ferredoxins should function as one-electron transfer proteins.

Physical characteristics and polarographic reduction mechanism of some oxazolones

1991 ◽  
Vol 69 (12) ◽  
pp. 1886-1892 ◽  
Author(s):  
M. I. Ismail
Keyword(s):  
Redox Potential ◽  
Coulomb Repulsion ◽  
Electrode Reaction ◽  
Alkaline Media ◽  
Third Wave ◽  
Polarographic Reduction ◽  
Buffer Solutions ◽  
Rate Of Hydrolysis ◽  
Hydrolysis Of ◽  
Electronic Transition Energy

The redox potential (ΔE1/2), electron affinity (EA), ionization potential (IP), coulomb repulsion integral (J12), and electronic transition energy (ECT) of several oxazolone derivatives in DMF were computed. A linear correlation was shown to exist between ΔE1/2 and ECT• The polarographic reduction was investigated in ethanolic-Theil buffer solutions. At pH ≤ 7.2, two waves were obtained representing the uptake of 2- and 4-electron steps respectively. In alkaline media, a third wave appeared seemingly a result of the hydrolysis of oxazolones. The rate of hydrolysis was determined and the electrode mechanism was elucidated and confirmed via spectrophotometric and coulometric analysis. Key words: oxazolones, polarography, electrochemistry, electrode reaction, spectrophotometry, redox potential.

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