scholarly journals Ligand-Centered Electrochemical Processes Enable CO2 Reduction with a Nickel Bis(triazapentadienyl) Complex

2018 ◽  
Author(s):  
Zachary Dubrawski ◽  
Joshua E. Heidebrecht ◽  
Braulio M. Puerta Lombardi ◽  
Alexander Hyla ◽  
Janina Willkomm ◽  
...  
Keyword(s):  
Transition Metal Complexes ◽  
Radical Anion ◽  
Co2 Reduction ◽  
Redox Activity ◽  
Decomposition Products ◽  
Electrochemical Processes ◽  
Reducing Conditions ◽  
Controlled Potential Electrolysis ◽  
Computational Data ◽  
Controlled Potential

We report the synthesis of Ni(TAPPy)<sub>2</sub> (TAPPy = 1,3,5-triazapentadienyl-2,4-bis(2-pyridyl)) and its reactivity with CO<sub>2</sub> under reducing conditions. Electrochemical reduction of Ni(TAPPy)<sub>2 </sub>under inert gas reveals that the complex accommodates up to two additional electrons, with DFT calculations indicating that electron density is delocalized almost exclusively onto the TAPPy ligand framework. The singly reduced product [K(crypt)][Ni(TAPPy)<sub>2</sub>] (crypt = 2.2.2-cryptand) has been synthesized, and its EPR data is consistent with having ligand-based radical anion character. Controlled potential electrolysis experiments reveal that reduced Ni(TAPPy)<sub>2</sub> converts CO<sub>2</sub> to form CO; however, spectroscopic and computational data indicate that deactivation readily occurs to form Ni(L)(CO)<i><sub>n</sub></i> compounds, CO<sub>3</sub><sup>2-</sup>, and carboxylated (RCOO<sup>-</sup>) ligand decomposition products. This study highlights that redox activity at the ligand can play an important role during the reduction of CO<sub>2</sub> using transition metal complexes.

scholarly journals Ligand-Centered Electrochemical Processes Enable CO2 Reduction with a Nickel Bis(triazapentadienyl) Complex

2018 ◽  
Author(s):  
Zachary Dubrawski ◽  
Joshua E. Heidebrecht ◽  
Braulio M. Puerta Lombardi ◽  
Alexander Hyla ◽  
Janina Willkomm ◽  
...  
Keyword(s):  
Transition Metal Complexes ◽  
Radical Anion ◽  
Co2 Reduction ◽  
Redox Activity ◽  
Decomposition Products ◽  
Electrochemical Processes ◽  
Reducing Conditions ◽  
Controlled Potential Electrolysis ◽  
Computational Data ◽  
Controlled Potential

We report the synthesis of Ni(TAPPy)<sub>2</sub> (TAPPy = 1,3,5-triazapentadienyl-2,4-bis(2-pyridyl)) and its reactivity with CO<sub>2</sub> under reducing conditions. Electrochemical reduction of Ni(TAPPy)<sub>2 </sub>under inert gas reveals that the complex accommodates up to two additional electrons, with DFT calculations indicating that electron density is delocalized almost exclusively onto the TAPPy ligand framework. The singly reduced product [K(crypt)][Ni(TAPPy)<sub>2</sub>] (crypt = 2.2.2-cryptand) has been synthesized, and its EPR data is consistent with having ligand-based radical anion character. Controlled potential electrolysis experiments reveal that reduced Ni(TAPPy)<sub>2</sub> converts CO<sub>2</sub> to form CO; however, spectroscopic and computational data indicate that deactivation readily occurs to form Ni(L)(CO)<i><sub>n</sub></i> compounds, CO<sub>3</sub><sup>2-</sup>, and carboxylated (RCOO<sup>-</sup>) ligand decomposition products. This study highlights that redox activity at the ligand can play an important role during the reduction of CO<sub>2</sub> using transition metal complexes.

Ligand-centered electrochemical processes enable CO2 reduction with a nickel bis(triazapentadienyl) complex

2019 ◽  
Vol 3 (5) ◽  
pp. 1172-1181 ◽  
Author(s):  
Zachary Dubrawski ◽  
Joshua Heidebrecht ◽  
Braulio M. Puerta Lombardi ◽  
Alexander S. Hyla ◽  
Janina Willkomm ◽  
...  
Keyword(s):  
Co2 Reduction ◽  
Electrochemical Processes ◽  
Reducing Conditions

We report the synthesis of a nickel bis(triazapentadienyl) complex and its reactivity with CO2 under reducing conditions.

Reduction of Gd6UO12 for the Synthesis of Gd6UO11

2013 ◽  
Vol 1514 ◽  
pp. 151-156
Author(s):  
Darío Pieck ◽  
Lionel Desgranges ◽  
Yves Pontillon ◽  
Pierre Matheron
Keyword(s):  
Heat Treatment ◽  
Xrd Analysis ◽  
Decomposition Products ◽  
Air Atmosphere ◽  
Reducing Conditions ◽  
Reducing Environment

ABSTRACTIn the present work, we focus on δ-Gd6UO12 phase and its stability under reducing conditions. This later point is interesting regarding reducing environment that could exist in some nuclear storage sites and that could possibly degrade δ–compounds. A polycrystalline δ-Gd6UO12 sample was prepared by sintering cubic-Gd2O3 and UO2 mixed powders under an air atmosphere. The resulting pellets were then characterized and reduced by heat treatment under an Ar with H2 5% atmosphere. XRD analysis of the sample after reduction did not confirm the reduction into Gd6UO11 but a decomposition of the δ-compound. Preliminary characterizations of these decomposition products are presented.

Polarographic Behaviour of Some Arylazotheophyllines

1993 ◽  
Vol 58 (9) ◽  
pp. 1978-1988
Author(s):  
Mohamed I. Ismail ◽  
Madlene L. Iskander
Keyword(s):  
Diffusion Coefficient ◽  
Model Compound ◽  
Aqueous Media ◽  
Chemical Characteristics ◽  
Polarographic Behaviour ◽  
Physico Chemical ◽  
Controlled Potential Electrolysis ◽  
Azo Group ◽  
Controlled Potential ◽  
Electrolysis Products

The polarographic behaviour of a series of arylazotheophyllines was studied in aqueous alcoholic buffer media and in DMF-0.1 M LiClO4 solution. The redox study gave evidence that the azo group is electroactive in aqueous as well as non-aqueous media. A mechanism interpreting the electrode process is proposed and confirmed through the identification of the controlled potential electrolysis products, the use of a model compound and the application of Hamett's σ-E relationship. The physico-chemical characteristics of these compounds, viz. the diffusion coefficient, dissociation constant, ionization potential and electron affinity, are also included.

CO2 reduction catalysis by tunable square-planar transition-metal complexes: a theoretical investigation using nitrogen-substituted carbon nanotube models

2017 ◽  
Vol 19 (43) ◽  
pp. 29068-29076 ◽  
Author(s):  
Yu-Te Chan ◽  
Ming-Kang Tsai
Keyword(s):  
Density Functional Theory ◽  
Carbon Nanotube ◽  
Transition Metal ◽  
Metal Complexes ◽  
Transition Metal Complexes ◽  
Density Functional ◽  
Co2 Reduction ◽  
Functional Theory ◽  
Square Planar ◽  
Planar Transition

The CO2 reduction capabilities of transition-metal-chelated nitrogen-substituted carbon nanotube models (TM-4N2v-CNT, TM = Fe, Ru, Os, Co, Rh, Ir, Ni, Pt or Cu) are characterized by density functional theory.

scholarly journals Electrochemical Behaviour of N′-(p-toluenesulphonyl)-3-methyl-4-(4′-substituted arylhydrazono) pyrazolin-5-ones

2012 ◽  
Vol 9 (4) ◽  
pp. 1864-1874
Author(s):  
V. Nagaraju ◽  
R. Sreenivasulu ◽  
P. Venkata Ramana
Keyword(s):  
Electrochemical Behaviour ◽  
Reduction Process ◽  
Effect Of Solvent ◽  
Buffer Solutions ◽  
Diffusion Controlled ◽  
Controlled Potential Electrolysis ◽  
Dc Polarography ◽  
Controlled Potential ◽  
Ph Range ◽  
And Diffusion

The electrochemical behaviour of N′-(p-toluenesulphonyl)-3-methyl-4-(4′-substituted arylhydrazono) pyrazolin-5-ones has been investigated at dme and gc electrodes in buffer solutions of pH 2.0, 4.0, 6.0, 8.0 and 10.0 using dc polarography and cyclic voltammetry and coulometry. The compounds exhibit one well defined wave in the entire pH range of study. The process is irreversible and diffusion controlled. Controlled potential electrolysis indicates the involvement of four electrons in the reduction process. The effect of solvent, cations and anions, temperature and substitutents on the mechanism of reduction has been studied. Based on the results obtained the mechanism of reduction has been suggested.

scholarly journals Electron Inventory of the Iron-Sulfur Scaffold Complex HypCD Essential in [NiFe]-Hydrogenase Cofactor Assembly

2021 ◽  
Author(s):  
Sven T. Stripp ◽  
Jonathan Oltmanns ◽  
Christina S. Müller ◽  
David Ehrenberg ◽  
Ramona Schlesinger ◽  
...  
Keyword(s):  
Redox Reactions ◽  
Redox Activity ◽  
Construction Site ◽  
Iron Ion ◽  
Paramagnetic Resonance ◽  
Iron Sulfur ◽  
Reducing Conditions ◽  
Reversible Redox ◽  
Electron Paramagnetic ◽  
Redox Conversion

The [4Fe-4S] cluster containing scaffold complex HypCD is the central construction site for the assembly of the [Fe](CN)2CO cofactor precursor of [NiFe]-hydrogenase. While the importance of the HypCD complex is well established, not much is known about the mechanism by which the CN– and CO ligands are transferred and attached to the iron ion. We developed an efficient protocol for the production and isolation of the functional HypCD complex that facilitated detailed spectroscopic investigations. The results obtained by UV/Vis-, electron paramagnetic Resonance (EPR)-, Resonance Raman-, Fourier-transform infrared (FTIR), and Mössbauer spectroscopy provide comprehensive evidence for an electron inventory fit to drive multi-electron redox reactions. We demonstrate the redox activity of the HypCD complex reporting the interconversion of the [4Fe-4S]2+/+ couple. Additionally, we observed a reversible redox conversion between the [4Fe-4S]2+ and a [3Fe-4S]+ cluster. MicroScale thermophoresis indicated preferable binding between the HypCD complex and its interaction partner HypEF under reducing conditions. Together, these results suggest a redox cascade involving the [4Fe-4S] cluster and a conserved disulfide bond of HypD that may facilitate the synthesis of the [Fe](CN)2CO cofactor precursor on the HypCD scaffold complex.

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