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.

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.

scholarly journals Electrochemistry-Induced Restructuring of Tin-Doped Indium Oxide Nanocrystal Films of Relevance to CO2 Reduction

2021 ◽  
Author(s):  
Tawney Knecht ◽  
Shannon W. Boettcher ◽  
James Hutchison
Keyword(s):  
Indium Oxide ◽  
Morphological Evolution ◽  
Co2 Reduction ◽  
Reducing Conditions ◽  
Cathodic Voltage ◽  
Nanocrystal Films ◽  
Primary Focus ◽  
Tin Metal ◽  
Reduction Of Co2

Abstract The electrochemical reduction of CO2 into fuels using renewable electricity presents an opportunity to utilize captured CO2. Electrocatalyst development has been the primary focus of research in this area. This is especially true at the nanoscale, where researchers have focused on understanding nanostructure-property relationships. However, electrocatalyst structure may evolve during operation. Indium- and tin-based oxides have been widely studied as electrocatalysts for CO2 reduction to formate, but evolution of these catalysts during operation is not well-characterized. Here, we report the evolution of nanoscale structure of tin-doped indium oxide nanocrystals under CO2 reduction conditions. We show that sparse monolayer nanocrystal films desorb from the electrode upon charging, but thicker nanocrystal films remain, likely due to increased number of physical contacts. Upon applying a cathodic voltage of -1.0 V vs RHE or greater, the original 10-nm diameter nanocrystals are no longer visible, and instead form a larger microstructural network. Elemental analysis suggests the network is an oxygen-deficient indium-tin metal alloy. We hypothesize that this morphological evolution is the result of nanocrystal sintering due to oxide reduction. These data provide insights into the morphological evolution tin-doped indium oxide nanocrystal electrocatalysts under reducing conditions and highlight the importance of post-electrochemical structural characterization of electrocatalysts.

Functional Characterization of PM6/13, a β3-specific (GPIIIa/CD61) Monoclonal Antibody that Shows Preferential Inhibition of Fibrinogen Binding over Fibronectin Binding to Activated Human Platelets

1998 ◽  
Vol 79 (01) ◽  
pp. 177-185 ◽  
Author(s):  
Ashia Siddiqua ◽  
Michael Wilkinson ◽  
Vijay Kakkar ◽  
Yatin Patel ◽  
Salman Rahman ◽  
...  
Keyword(s):  
Monoclonal Antibody ◽  
Platelet Aggregation ◽  
Platelet Rich Plasma ◽  
Functional Characterization ◽  
Human Platelets ◽  
Western Blots ◽  
Activated Platelets ◽  
Reducing Conditions ◽  
Fibronectin Binding

SummaryWe report the characterization of a monoclonal antibody (MAb) PM6/13 which recognises glycoprotein IIIa (GPIIIa) on platelet membranes and in functional studies inhibits platelet aggregation induced by all agonists examined. In platelet-rich plasma, inhibition of aggregation induced by ADP or low concentrations of collagen was accompanied by inhibition of 5-hydroxytryptamine secretion. EC50 values were 10 and 9 [H9262]g/ml antibody against ADP and collagen induced responses respectively. In washed platelets treated with the cyclooxygenase inhibitor, indomethacin, PM6/13 inhibited platelet aggregation induced by thrombin (0.2 U/ml), collagen (10 [H9262]g/ml) and U46619 (3 [H9262]M) with EC50 = 4, 8 and 4 [H9262]g/ml respectively, without affecting [14C]5-hydroxytryptamine secretion or [3H]arachidonate release in appropriately labelled cells. Studies in Fura 2-labelled platelets revealed that elevation of intracellular calcium by ADP, thrombin or U46619 was unaffected by PM6/13 suggesting that the epitope recognised by the antibody did not influence Ca2+ regulation. In agreement with the results from the platelet aggregation studies, PM6/13 was found to potently inhibit binding of 125I-fibrinogen to ADP activated platelets. Binding of this ligand was also inhibited by two other MAbs tested, namely SZ-21 (also to GPIIIa) and PM6/248 (to the GPIIb-IIIa complex). However when tested against binding of 125I-fibronectin to thrombin stimulated platelets, PM6/13 was ineffective in contrast with SZ-21 and PM6/248, that were both potent inhibitors. This suggested that the epitopes recognised by PM6/13 and SZ-21 on GPIIIa were distinct. Studies employing proteolytic dissection of 125I-labelled GPIIIa by trypsin followed by immunoprecipitation with PM6/13 and analysis by SDS-PAGE, revealed the presence of four fragments at 70, 55, 30 and 28 kDa. PM6/13 did not recognize any protein bands on Western blots performed under reducing conditions. However Western blotting analysis with PM6/13 under non-reducing conditions revealed strong detection of the parent GP IIIa molecule, of trypsin treated samples revealed recognition of an 80 kDa fragment at 1 min, faint recognition of a 60 kDa fragment at 60 min and no recognition of any product at 18 h treatment. Under similar conditions, SZ-21 recognized fragments at 80, 75 and 55 kDa with the 55kDa species persisting even after 18 h trypsin treatment. These studies confirm the epitopes recognised by PM6/13 and SZ-21 to be distinct and that PM6/13 represents a useful tool to differentiate the characteristics of fibrinogen and fibronectin binding to the GPIIb-IIIa complex on activated platelets.

Energy saving technology for sintering of black bricks from high-siliceous clay

MRS Advances ◽  
2020 ◽  
Vol 5 (61) ◽  
pp. 3123-3131
Author(s):  
Mario Flores Nicolas ◽  
Marina Vlasova ◽  
Pedro Antonio Márquez Aguilar ◽  
Mykola Kakazey ◽  
Marcos Mauricio Chávez Cano ◽  
...  
Keyword(s):  
Low Temperature ◽  
Oxygen Deficiency ◽  
Glass Ceramics ◽  
Total Content ◽  
Ceramic Materials ◽  
Ternary Mixtures ◽  
High Porosity ◽  
Reducing Conditions ◽  
Binary And Ternary Mixtures ◽  
Dark Color

AbstractThe low-temperature synthesis of bricks prepared from high-siliceous clays by the method of plastic molding of blanks was used. For the preparation of brick blanks, binary and ternary mixtures of high-siliceous clays, black sand, and bottle glass cullet were used. Gray-black low-porosity and high-porosity ceramics was obtained by sintering under conditions of oxygen deficiency. It has been established that to initiate plastic in mixtures containing high-siliceous clay, it is necessary to add montmorillonite/bentonite additives, carry out low-temperature sintering, and introduce low-melting glass additives with a melting point ranging from 750 to 800 °C. The performed investigations have shown that the sintering of mixtures with a total content of iron oxide of about 5 wt% under reducing conditions at Tsint. = 800°C for 8 h leads to the formation of glass ceramics consisting of quartz, feldspars, and a phase. The main sources of the appearance of a dark color is the formation of [Fe3+O4]4- and [Fe3+O6]9- anions in the composition of the glass phase and feldspars. By changing the contents of clay, sand, and glass in sintering, it is possible to obtain two types of ceramic materials: (a) in the form of building bricks and (b) in the form of porous fillers.

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