scholarly journals Quest for Compounds at the Verge of Charge Transfer Instabilities: The Case of Silver(II) Chloride †

Crystals ◽  
2019 ◽  
Vol 9 (8) ◽  
pp. 423 ◽  
Author(s):  
Mariana Derzsi ◽  
Adam Grzelak ◽  
Paweł Kondratiuk ◽  
Kamil Tokár ◽  
Wojciech Grochala

Electron-transfer processes constitute one important limiting factor governing stability of solids. One classical case is that of CuI2, which has never been prepared at ambient pressure conditions due to feasibility of charge transfer between metal and nonmetal (CuI2 → CuI + ½ I2). Sometimes, redox instabilities involve two metal centers, e.g., AgO is not an oxide of divalent silver but rather silver(I) dioxoargentate(III), Ag(I)[Ag(III)O2]. Here, we look at the particularly interesting case of a hypothetical AgCl2 where both types of redox instabilities operate simultaneously. Since standard redox potential of the Ag(II)/Ag(I) redox pair reaches some 2 V versus Normal Hydrogen Electrode (NHE), it might be expected that Ag(II) would oxidize Cl− anion with great ease (standard redox potential of the ½ Cl2/Cl− pair is + 1.36 V versus Normal Hydrogen Electrode). However, ionic Ag(II)Cl2 benefits from long-distance electrostatic stabilization to a much larger degree than Ag(I)Cl + ½ Cl2, which affects relative stability. Moreover, Ag(II) may disproportionate in its chloride, just like it does in an oxide; this is what AuCl2 does, its formula corresponding in fact to Au(I)[Au(III)Cl4]. Formation of polychloride substructure, as for organic derivatives of Cl3− anion, is yet another possibility. All that creates a very complicated potential energy surface with a few chemically distinct minima i.e., diverse polymorphic forms present. Here, results of our theoretical study for AgCl2 will be presented including outcome of evolutionary algorithm structure prediction method, and the chemical identity of the most stable form will be uncovered together with its presumed magnetic properties. Contrary to previous rough estimates suggesting substantial instability of AgCl2, we find that AgCl2 is only slightly metastable (by 52 meV per formula unit) with respect to the known AgCl and ½ Cl2, stable with respect to elements, and simultaneously dynamically (i.e., phonon) stable. Thus, our results point out to conceivable existence of AgCl2 which should be targeted via non-equilibrium approaches.

2011 ◽  
Vol 134 (24) ◽  
pp. 244508 ◽  
Author(s):  
Francesca Costanzo ◽  
Marialore Sulpizi ◽  
Raffaele Guido Della Valle ◽  
Michiel Sprik

1969 ◽  
Vol 21 (02) ◽  
pp. 325-331 ◽  
Author(s):  
J.C Brown ◽  
S.M Lavelle ◽  
P.N Sawyer

SummaryThe triggering of electrical thrombosis on electrodes depends on the coagulation steps prior to factor IX activation. Factor XII may be responsible for this phenomenon. The platelet may also play a role. It has been shown that platelet deposition is visible at potentials more positive than +0.3 V versus the normal hydrogen electrode. The same compounds which inhibit intravascular thrombosis will also impair electrical thrombosis.


2019 ◽  
Vol 116 (52) ◽  
pp. 26353-26358 ◽  
Author(s):  
Yanming Liu ◽  
Xinfei Fan ◽  
Animesh Nayak ◽  
Ying Wang ◽  
Bing Shan ◽  
...  

Electrochemical reduction of CO2to multicarbon products is a significant challenge, especially for molecular complexes. We report here CO2reduction to multicarbon products based on a Ru(II) polypyridyl carbene complex that is immobilized on an N-doped porous carbon (RuPC/NPC) electrode. The catalyst utilizes the synergistic effects of the Ru(II) polypyridyl carbene complex and the NPC interface to steer CO2reduction toward C2 production at low overpotentials. In 0.5 M KHCO3/CO2aqueous solutions, Faradaic efficiencies of 31.0 to 38.4% have been obtained for C2 production at −0.87 to −1.07 V (vs. normal hydrogen electrode) with 21.0 to 27.5% for ethanol and 7.1 to 12.5% for acetate. Syngas is also produced with adjustable H2/CO mole ratios of 2.0 to 2.9. The RuPC/NPC electrocatalyst maintains its activity during 3-h CO2-reduction periods.


2015 ◽  
Vol 17 (40) ◽  
pp. 27103-27108 ◽  
Author(s):  
Ryota Jono ◽  
Yoshitaka Tateyama ◽  
Koichi Yamashita

We demonstrate the redox potential calculations relative to the normal hydrogen electrode (NHE) in non-aqueous solution by density functional theory based molecular dynamics (DFT-MD) simulation.


1969 ◽  
Vol 47 (20) ◽  
pp. 3729-3736 ◽  
Author(s):  
N. A. Hampson ◽  
J. B. Lee ◽  
J. R. Morley ◽  
B. Scanlon

Primary aliphatic amines are rapidly oxidized using a silver electrode at potentials more positive than 0.6 V normal hydrogen electrode (n.h.e.) in aqueous alkali. Primary aliphatic amines with a mono-substituted α-carbon atom give the corresponding nitrile and aldehyde, α,α-disubstituted ones give the corresponding ketone, and α,α,α-trisubstituted ones give the corresponding alcohol, nitro-compound, and unsaturated hydrocarbons. Some evidence for the reaction pathway is presented. The effect of amine on the kinetic parameters for Ag2O formation is reported.


2015 ◽  
Vol 81 (16) ◽  
pp. 5387-5394 ◽  
Author(s):  
Xin Wang ◽  
Ping Yu ◽  
Cuiping Zeng ◽  
Hongrui Ding ◽  
Yan Li ◽  
...  

ABSTRACTThe utilization byAlcaligenes faecalisof electrodes as the electron donor for denitrification was investigated in this study. The denitrification rate ofA. faecaliswith a poised potential was greatly enhanced compared with that of the controls without poised potentials. For nitrate reduction, althoughA. faecaliscould not reduce nitrate, at three poised potentials of +0.06, −0.06, and −0.15 V (versus normal hydrogen electrode [NHE]), the nitrate was partially reduced with −0.15- and −0.06-V potentials at rates of 17.3 and 28.5 mg/liter/day, respectively. The percentages of reduction for −0.15 and −0.06 V were 52.4 and 30.4%, respectively. Meanwhile, for nitrite reduction, the poised potentials greatly enhanced the nitrite reduction. The nitrite reduction rates for three poised potentials (−0.06, −0.15, and −0.30 V) were 1.98, 4.37, and 3.91 mg/liter/h, respectively. When the potentials were cut off, the nitrite reduction rate was maintained for 1.5 h (from 2.3 to 2.25 mg/liter/h) and then greatly decreased, and the reduction rate (0.38 mg/liter/h) was about 1/6 compared with the rate (2.3 mg/liter/h) when potential was on. Then the potentials resumed, but the reduction rate did not resume and was only 2 times higher than the rate when the potential was off.


1933 ◽  
Vol 16 (6) ◽  
pp. 859-873 ◽  
Author(s):  
L. Michaelis ◽  
Edgar S. Hill

The tabulation gives the normal potentials of the various indicators at 30°C.; referred to the normal hydrogen electrode, the accuracy is estimated to be ±0.002 volt. Normal potentials of the viologens at 30°C.: Methyl viologen –0.446 volts Ethyl viologen –0.449 volts Betaine viologen –0.444 volts Benzyl viologen –0.359 volts Supposing some solution brings about a coloration of one of these indicators to the extent of A per cent of the maximum color, the oxidation-reduction potential of this solution is E = Eo – 0.06 log See PDF for Equation where Eo is the normal potential according to the above tabulation. This normal potential is independent of pH.


2013 ◽  
Vol 25 (18) ◽  
pp. 184008 ◽  
Author(s):  
S Nakabayashi ◽  
R Shinozaki ◽  
Y Senda ◽  
H Y Yoshikawa

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