Fluorescent Organo-Antimony Compounds as Precursors for Syntheses of Redox-Active Trimeric and Dimeric Alkali Metal Antimonides: An Insight into Electron Transfer Reduction Processes

2022 ◽  
Author(s):  
Sudipta Roy ◽  
Ekta Nag ◽  
Aditya Kulkarni ◽  
Sai Manoj N.V.T. Gorantla ◽  
Nico Graw ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Alkali Metal ◽  
Reduction Processes ◽  
Redox Active ◽  
Electron Reduction ◽  
Insight Into

(Tip)2SbCl (1, Tip = 2,4,6-triisopropylphenyl) has been utilized as a precursor for the synthesis of distibane (Tip)4Sb2 (4) by one-electron reduction using KC8. Two-electrons reduction of 1 and 4 afforded...

A Sensitive Catalytic Wave Formed by Electrochemical Reduction of Morin in the Presence of an Oxidant KIO3

2014 ◽  
Vol 67 (4) ◽  
pp. 620 ◽  
Author(s):  
Sikun Cheng ◽  
Yanhua Dong ◽  
Yayan Wu ◽  
Junfeng Song ◽  
Chuan Zhao
Keyword(s):  
Electron Transfer ◽  
Free Radical ◽  
Double Bond ◽  
Phosphate Buffer ◽  
Primary Alcohol ◽  
Radical Intermediate ◽  
Reduction Processes ◽  
Catalytic Wave ◽  
Free Radical Intermediate ◽  
Electron Reduction

The investigation of the electrogenerated free radical of morin reacting with an oxidant is helpful in understanding its antioxidant pharmacology. In phosphate buffer (pH 5.6 ± 0.1), the reduction of morin proceeds with a one-electron transfer of the C=O double bond into a free radical intermediate, which then delivers the final primary alcohol via a one-electron reduction. When an oxidant KIO3 is present, the free radical intermediate of morin is oxidized to regenerate the original ‘C=O’ bond. Further reduction processes are effectively inhibited, resulting in a sensitive catalytic peak, with the peak current enhanced 70 times.

scholarly journals Structures of the Iron-Sulfur Flavoproteins from Methanosarcina thermophila and Archaeoglobus fulgidus

2005 ◽  
Vol 187 (11) ◽  
pp. 3848-3854 ◽  
Author(s):  
Susana L. A. Andrade ◽  
Francisco Cruz ◽  
Catherine L. Drennan ◽  
Vijay Ramakrishnan ◽  
Douglas C. Rees ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Three Dimensional ◽  
Archaeoglobus Fulgidus ◽  
Flavin Mononucleotide ◽  
Methanosarcina Thermophila ◽  
Sulfate Reducing ◽  
Iron Sulfur ◽  
Redox Active ◽  
Sequence Homologies ◽  
Insight Into

ABSTRACT Iron-sulfur flavoproteins (ISF) constitute a widespread family of redox-active proteins in anaerobic prokaryotes. Based on sequence homologies, their overall structure is expected to be similar to that of flavodoxins, but in addition to a flavin mononucleotide cofactor they also contain a cubane-type [4Fe:4S] cluster. In order to gain further insight into the function and properties of ISF, the three-dimensional structures of two ISF homologs, one from the thermophilic methanogen Methanosarcina thermophila and one from the hyperthermophilic sulfate-reducing archaeon Archaeoglobus fulgidus, were determined. The structures indicate that ISF assembles to form a tetramer and that electron transfer between the two types of redox cofactors requires oligomerization to juxtapose the flavin mononucleotide and [4Fe:4S] cluster bound to different subunits. This is only possible between different monomers upon oligomerization. Fundamental differences in the surface properties of the two ISF homologs underscore the diversity encountered within this protein family.

scholarly journals Stabilization of a Triplet Diradical on a Binuclear palladium(II) Dipyrrindione

2021 ◽  
Author(s):  
Clayton J. Curtis ◽  
Andrei V. Astashkin ◽  
Jeanet Conradie ◽  
Abhik Ghosh ◽  
Elisa Tomat
Keyword(s):  
Metal Complexes ◽  
Functional Materials ◽  
Dinuclear Complex ◽  
Redox Active Ligands ◽  
Reduction Processes ◽  
Redox Active ◽  
X Band ◽  
The Rich ◽  
Electron Reduction ◽  
Computational Analyses

Porphyrins and other macrocyclic oligopyrroles form a versatile class of redox-active ligands and electron reservoirs. The stabilization of unpaired electrons within oligopyrrolic π systems adds to the available reactivity pathways and spin states of metal complexes for applications in catalysis and functional materials. In this context, bidentate dipyrrindiones are emerging as compact platforms for one-electron redox chemistry in transition metal complexes. We report the synthesis of a bis(aqua) palladium(II) dipyrrindione complex and its deprotonation-driven dimerization to form a hydroxo-bridged dinuclear complex. Electrochemical, spectroelectrochemical, and computational analyses indicate the accessibility of two reduction processes on the dipyrrindione frameworks of the dinuclear complex. The product of a two-electron reduction by cobaltocene was isolated and characterized. In the solid state, this cobaltoceni- um salt features a folded dianionic complex maintaining the hydroxo bridges between the divalent palladium centers. X- band and Q-band EPR spectroscopic experiments and DFT computational analysis allow assignment of the dianionic species as a triplet diradical supported by the dipyrrindione ligands. These dipyrroles, which are also known as propentdyopents and were initially isolated as urinary pigments and heme metabolites, extend the rich chemistry of bidentate dipyrrin ligands to include the stabilization of ligand-centered radicals.

scholarly journals Stabilization of a Triplet Diradical on a Binuclear palladium(II) Dipyrrindione

2021 ◽  
Author(s):  
Clayton J. Curtis ◽  
Andrei V. Astashkin ◽  
Jeanet Conradie ◽  
Abhik Ghosh ◽  
Elisa Tomat
Keyword(s):  
Metal Complexes ◽  
Functional Materials ◽  
Dinuclear Complex ◽  
Redox Active Ligands ◽  
Reduction Processes ◽  
Redox Active ◽  
X Band ◽  
The Rich ◽  
Electron Reduction ◽  
Computational Analyses

Porphyrins and other macrocyclic oligopyrroles form a versatile class of redox-active ligands and electron reservoirs. The stabilization of unpaired electrons within oligopyrrolic π systems adds to the available reactivity pathways and spin states of metal complexes for applications in catalysis and functional materials. In this context, bidentate dipyrrindiones are emerging as compact platforms for one-electron redox chemistry in transition metal complexes. We report the synthesis of a bis(aqua) palladium(II) dipyrrindione complex and its deprotonation-driven dimerization to form a hydroxo-bridged dinuclear complex. Electrochemical, spectroelectrochemical, and computational analyses indicate the accessibility of two reduction processes on the dipyrrindione frameworks of the dinuclear complex. The product of a two-electron reduction by cobaltocene was isolated and characterized. In the solid state, this cobaltoceni- um salt features a folded dianionic complex maintaining the hydroxo bridges between the divalent palladium centers. X- band and Q-band EPR spectroscopic experiments and DFT computational analysis allow assignment of the dianionic species as a triplet diradical supported by the dipyrrindione ligands. These dipyrroles, which are also known as propentdyopents and were initially isolated as urinary pigments and heme metabolites, extend the rich chemistry of bidentate dipyrrin ligands to include the stabilization of ligand-centered radicals.

Room Temperature Alkali Metal Reduction of Carbon Dioxide

2020 ◽  
Author(s):  
Lucas A. Freeman ◽  
Akachukwu D. Obi ◽  
Haleigh R. Machost ◽  
Andrew Molino ◽  
Asa W. Nichols ◽  
...  
Keyword(s):  
Alkali Metal ◽  
Alkali Metals ◽  
Room Temperature ◽  
Chemical Reduction ◽  
Bond Cleavage ◽  
Open Shell ◽  
Metal Reduction ◽  
One Pot ◽  
Earth Abundant ◽  
Electron Reduction

The reduction of the relatively inert carbon–oxygen bonds of CO<sub>2</sub> to access useful CO<sub>2</sub>-derived organic products is one of the most important fundamental challenges in synthetic chemistry. Facilitating this bond-cleavage using earth-abundant, non-toxic main group elements (MGEs) is especially arduous because of the difficulty in achieving strong inner-sphere interactions between CO<sub>2</sub> and the MGE. Herein we report the first successful chemical reduction of CO<sub>2</sub> at room temperature by alkali metals, promoted by a cyclic(alkyl)(amino) carbene (CAAC). One-electron reduction of CAAC-CO<sub>2</sub> adduct (<b>1</b>) with lithium, sodium or potassium metal yields stable monoanionic radicals clusters [M(CAAC–CO<sub>2</sub>)]<sub>n</sub>(M = Li, Na, K, <b> 2</b>-<b>4</b>) and two-electron alkali metal reduction affords open-shell, dianionic clusters of the general formula [M<sub>2</sub>(CAAC–CO<sub>2</sub>)]<sub>n </sub>(<b>5</b>-<b>8</b>). It is notable that these crystalline clusters of reduced CO<sub>2</sub> may also be isolated via the “one-pot” reaction of free CO<sub>2</sub> with free CAAC followed by the addition of alkali metals – a reductive process which does not occur in the absence of carbene. Each of the products <b>2</b>-<b>8</b> were investigated using a combination of experimental and theoretical methods.<br>

scholarly journals Autocatalytic photoredox Chan-Lam coupling of free diaryl sulfoximines with arylboronic acids

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Cong Wang ◽  
Hui Zhang ◽  
Lucille A. Wells ◽  
Tian Liu ◽  
Tingting Meng ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Hydrogen Atom Abstraction ◽  
Coupling Reactions ◽  
Ambient Light ◽  
Environmental Friendliness ◽  
Copper Species ◽  
Arylboronic Acids ◽  
Ligand Free ◽  
Byproduct Formation ◽  
Electron Reduction

AbstractN-Arylation of NH-sulfoximines represents an appealing approach to access N-aryl sulfoximines, but has not been successfully applied to NH-diaryl sulfoximines. Herein, a copper-catalyzed photoredox dehydrogenative Chan-Lam coupling of free diaryl sulfoximines and arylboronic acids is described. This neutral and ligand-free coupling is initiated by ambient light-induced copper-catalyzed single-electron reduction of NH-sulfoximines. This electron transfer route circumvents the sacrificial oxidant employed in traditional Chan-Lam coupling reactions, increasing the environmental friendliness of this process. Instead, dihydrogen gas forms as a byproduct of this reaction. Mechanistic investigations also reveal a unique autocatalysis process. The C–N coupling products, N-arylated sulfoximines, serve as ligands along with NH-sulfoximine to bind to the copper species, generating the photocatalyst. DFT calculations reveal that both the NH-sulfoximine substrate and the N-aryl product can ligate the copper accounting for the observed autocatalysis. Two energetically viable stepwise pathways were located wherein the copper facilitates hydrogen atom abstraction from the NH-sulfoximine and the ethanol solvent to produce dihydrogen. The protocol described herein represents an appealing alternative strategy to the classic oxidative Chan-Lam reaction, allowing greater substrate generality as well as the elimination of byproduct formation from oxidants.

scholarly journals Insight to Microbial Fe(III) Reduction Mediated by Redox-Active Humic Acids with Varied Redox Potentials

2021 ◽  
Vol 18 (13) ◽  
pp. 6807
Author(s):  
Jingtao Duan ◽  
Zhiyuan Xu ◽  
Zhen Yang ◽  
Jie Jiang
Keyword(s):  
Molecular Weight ◽  
Electron Transfer ◽  
Humic Acids ◽  
Weight Fraction ◽  
Electrochemical Analysis ◽  
Microbial Reduction ◽  
Redox Potentials ◽  
Groundwater Environment ◽  
Redox Active ◽  
Different Molecular Weight

Redox-active humic acids (HA) are ubiquitous in terrestrial and aquatic systems and are involved in numerous electron transfer reactions affecting biogeochemical processes and fates of pollutants in soil environments. Redox-active contaminants are trapped in soil micropores (<2 nm) that have limited access to microbes and HA. Therefore, the contaminants whose molecular structure and properties are not damaged accumulate in the soil micropores and become potential pollution sources. Electron transfer capacities (ETC) of HA reflecting redox activities of low molecular weight fraction (LMWF, <2.5) HA can be detected by an electrochemical method, which is related to redox potentials (Eh) in soil and aquatic environments. Nevertheless, electron accepting capacities (EAC) and electron donating capacities (EDC) of these LMWF HA at different Eh are still unknown. EDC and EAC of different molecular weight HA at different Eh were analyzed using electrochemical methods. EAC of LMWF at −0.59 V was 12 times higher than that at −0.49 V, while EAC increased to 2.6 times when the Eh decreased from −0.59 V to −0.69 V. Afterward, LMWF can act as a shuttle to stimulate microbial Fe(III) reduction processes in microbial reduction experiments. Additionally, EAC by electrochemical analysis at a range of −0.49–−0.59 V was comparable to total calculated ETC of different molecular weight fractions of HA by microbial reduction. Therefore, it is indicated that redox-active functional groups that can be reduced at Eh range of −0.49–−0.59 are available to microbial reduction. This finding contributes to a novel perspective in the protection and remediation of the groundwater environment in the biogeochemistry process.

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