Production of Metallic Titanium by Electrowinning in Molten Salts of Titanium Oxycarbide Anode

The electrochemical behavior of Ti3+ in LiCl-LiF-TiF3 salt was investigated by cyclic and square wave voltammetries at 853 K. Both methods confirm the presence of a single reduction wave of Ti3+ ions to metal, at a potential of −2.3 V vs. Cl2/Cl−. The closeness of the potentials of TiCxOy dissolution and Ti3+/Ti4+ wave is an issue during the electrorefining of the anode. A low current density has to be applied to stay within the titanium oxycarbide dissolution and avoid the formation of Ti4+. The titanium deposition was studied by electrorefining of a titanium metal plate in LiCl-LiF-TiF3 (0.62 mol/kg). The cathodic deposit analysis by XRD and SEM confirms the formation of titanium metal with an average grain size of 150 µm. The faradic deposition yields are above 85% and constant between 60 and 160 mA/cm2.

Electrochemical and Molecular Assessment of Quinones as CO2-Binding Redox Molecules for Carbon Capture

The complexation and decomplexation of CO2 with a series of quinones of different basicity during electrochemical cycling in dimethylformamide solutions were studied systematically by cyclic voltammetry. In the absence of CO2, all quinones exhibited two well-separated reduction waves. For weakly complexing quinones, a positive shift in the second reduction wave was observed in the presence of CO2, corresponding to the dianion quinone-CO2 complex formation. The peak position and peak height of the first re-duction wave were unchanged, indicating no formation of complexes between the semiquinones and CO2. The relative heights of both reduction waves remained constant. In the case of strongly complexing quinones, the second reduction wave disappeared while the peak height of the first reduction wave approximately doubled, indicating that the two electrons transferred simultaneously at this potential. The observed voltammograms were rationalized through several equilibrium arguments. Both weakly and strongly complexing quinones underwent either stepwise or concerted mechanisms of oxidation and CO2 dissociation depending on the sweep rate in the cyclic voltammetric experiments. Relative to stepwise oxidation, the concerted process requires a more positive electrode potential to remove the electron from the carbonate complexes to release CO2 and regenerate the quinone. For weakly complexing quinones, the stepwise process corresponds to oxidation of the uncomplexed dianion and accompanying equilibrium shift, while for strongly complexing quinones the stepwise process would correspond to the oxidation of mono(carbonate) dianion to the complexed semiquinone and accompanying equilibrium shift. This study provides a mechanistic interpretation of the interactions that lead to the formation of quinone-CO2 complexes required for the potential development of an energy efficient electrochemical separation process and discusses important considerations for practical implementation of CO2 capture in the presence of oxygen with lower vapor pressure solvents.

Photophysical and Electrocatalytic Properties of Rhenium(I) Triazole-Based Complexes

A series of [Re(N^N)(CO)3(Cl)] (N^N = diimine) complexes based on 4-(pyrid-2-yl)-1,2,3-triazole (1), 1-benzyl-4-(pyrimidin-2-yl)-1,2,3-triazole (2), and 1-benzyl-4-(pyrazin-2-yl)-1,2,3-triazole (3) diimine ligands were prepared and their photophysical and electrochemical properties were characterized. The ligand-based reduction wave is shown to be highly sensitive to the nature of the triazole-based ligand, with the peak potential shifting by up to 600 mV toward more positive potential from 1 to 3. All three complexes are phosphorescent in solution at room temperature with λmax ranging from 540 nm (1) to 638 nm (3). Interestingly, the complexes appear to show inverted energy-gap law behaviour (τ = 43 ns for 1 versus 92 ns for 3), which is tentatively interpreted as reduced thermal accessibility of metal-centred (3MC) states from photoexcited metal to ligand charge transfer (3MLCT) states upon stabilisation of the N^N-centred lowest unoccupied molecular orbital (LUMO). The photophysical characterisation, supported by computational data, demonstrated a progressive stabilization of the LUMO from complex 1 to 3, which results in a narrowing of the HOMO–LUMO energy gap (HOMO = highest occupied molecular orbital) across the series and, correspondingly, red-shifted electronic absorption and photoluminescence spectra. The two complexes bearing pyridyl (1) and pyrimidyl (2) moieties, respectively, showed a modest ability to catalyse the electroreduction of CO2, with a peak potential at ca. −2.3 V versus Fc/Fc+. The catalytic wave that is observed in the cyclic voltammograms is slightly enhanced by the addition of water as a proton source.

An Ru-Substituted Tris(ethynyl)methyl Cation: Synthesis, Properties, and Structure of [{Cp(dppe)Ru(C≡C)}3C]PF6·C6H6

The dark blue complex [{Cp(dppe)Ru(C≡C)}3C]PF6 1 (Cp=cyclopentadienyl, dppe=1,2-bis(diphenylphosphino)ethane) was obtained in 46% yield by treatment of Ru(C≡CH)(dppe)Cp with CuCl/TMEDA (tetramethylethanediamine), followed by KOH and [NH4]PF6 in acetone; it was accompanied by known complexes {Cp(dppe)Ru}C≡CC≡C{Ru(dppe)Cp} 2 (22%) and yellow [1,3-{Cp(dppe)Ru}2C4H3]PF6 3 (2.6%). The structure of the cationic fragment of 1 in its benzene solvate consists of a central planar C attached to three C≡CRu(dppe)Cp fragments. The cation of 3 consists of a cyclobuten-1,3-diyl group bearing two Ru(dppe)Cp groups. The 13C NMR resonance of the central C in 1 is found at δ 66.11. The cyclic voltammogram of 1 contains three irreversible oxidation waves at +0.87, +0.79, and +0.25V, together with a reversible reduction wave at −1.38V (versus FeCp2/[FeCp2]+).

Metal Complexes of π-Expanded Ligands (3): Synthesis and Characterization of tris[2-[(octylimino)methyl]-1-pyrenolato-N,O] cobalt(III)

The reactions of Co(OAc)2 with two equivalents of 1-hydroxy-2-[(octylimino)methyl-pyrene L, performed in air, lead to the formation of the cobalt(III) complex, tris[2-[(octylimino)methyl]-1-pyrenolato-N,O] cobalt(III) CoL3, accommodating three chelating pyrene-based salicylaldiminato-type ligands. The complex CoL3 and the referent tris(salicylaldiminato) cobalt(III) 1’(CoIII) were obtained in excellent yields, and their characterisation by 1H NMR, IR, mass spectroscopy, elemental analysis and X-ray diffraction revealed that they were of diamagnetic nature, octahedral geometry with the cobalt centre and meridional configuration. The redox behaviour of these complexes shows an irreversible reduction wave with a peak potential in the range -1.9 to -1.2 V. Upon reduction, the complexes decompose, giving rise to a redox pattern compatible with the formation of bis[2-[(octylimino)methyl]-1-pyrenolato-N,O] cobalt(II). Keywords: Coordination chemistry, Cobalt, Pyrene, π-Expanded ligand, Salicylaldimine. References: [1] Luong Xuan Dien, Ken-ichi Yamashita, Motoko S. Asano, Ken-ichi Sugiura, Synthesis of a pyrene-based π-expanded ligand and the corresponding platinum(II) complex, Bis[2-[(octylimino)methyl]-1-pyrenolato-N,O] platinum(II), Inorganica Chimica Acta, 432 (2015) 103-108. https://doi.org/10.1016/j.ica. 2015.03.038.[2] Luong Xuan Dien, Ken-ichi Yamashita, Ken-ichi Sugiura, Metal Complexes of π-Expanded Ligands (2): Synthesis and characterizations of bis[2-[(octylimino)methyl]-1-pyrenolato-N,O] palladium(II) and the stabilized vacant dx2-y2 orbital, Polyhedron, 102 (2015) 69-74. https://doi.org/10.1016/j.poly.2015.07.043.[3] Luong Xuan Dien, Nguyen Xuan Truong, Ngo Duc Quan, Ken-ichi Yamashita, Ken-ichi Sugiura, Syntheses and structures of Ni(II) complexes containing 2 alkyliminomethyl pyrene ligands, VNU Journal of Science, 34 (4) (2018) 16-20. https://doi.org/10.25073/2588-1140/vnunst.4809.[4] Robert D. Jones, David A. Summerville, Fred. Basolo, Synthetic oxygen carriers related to biological systems, Chem. Rev., 79 (1979) 139-179. https://doi.org/10.1021/cr60318a002.[5] Kuninobu Kasuga, Takeo Nagahara, Akira Tsuge, Kunihisa Sogabe, Yasuo Yamamoto, The preparation and some properties of cobalt(II) schiff base complexes and their molecular oxygen adducts, Bull. Chem. Soc. Jpn., 56 (1983) 95-98. https://doi.org/10.1246/bcsj.56.95.[6] H. Pellissier, H. Clavier, Enantioselective cobalt-catalyzed transformations, Chem. Rev., 114 (2014) 2775-2823. https://doi.org/10.1021/ cr4004055.[7] R. H. Crabtree, Energy Production and Storage: Inorganic Chemical Strategies for a Warming World, first ed., John Wiley & Sons, West Sussex, 2010.[8] P. Sravanthi, C. Chandrakala, KS. Nagaraja, B. Jeyaraj, Development of cobalt Schiff base precursors for nanocrystalline cobalt oxide thin film by thermal CVD method, International journal of pharmaceutical, chemical and biological sciences, 5(1) (2015) 112-125. http:/ /www.ijpcbs.com/files/volume5-1-2015/12.pdf.[9] B. O. West, Complexes of tervalent cobalt with N-substituted salicylideneimines, J. Chem. Soc., 0 (1960) 4944-4947. https://doi.org/10. 1039/JR9600004944.[10] A. Ourari, Y. Ouennoughi, S. Bouacida, Tris(2-{[2-(4-meth¬oxy¬phen¬yl)eth¬yl]imino-meth¬yl}phenolato-κ2N,O1)cobalt(III), Acta Cryst., E68 (2012) m803-m804. https://doi.org/10.1107/ S1600536812023033.[11] A. Chakravorty , R. H. Holm, Identification of the geometrical isomers of some tris-chelate cobalt(III) complexes by nuclear resonance, Inorg. Chem., 3 (1964) 1521-1524. https://doi. org/10.1021/ic50021a010.[12] S. Li, S.-B. Wang, K. Tang, Y.-F. Ma, Tris [2-(propyliminomethyl)phenolato-κ2 N,O]cobalt(III), Acta Cryst., E64 (2008) m823. https://doi.org/ 10.1107/S1600536808014074.

The philosophical foundations of quantum computer modeling

The source of some problems of the quantum mechanics is the observer’s influence on the system. In particular, such problems include the reduction wave function, which forces physicists to talk about “hidden parameters” and the incompleteness of quantum mechanics. Measurements of a quantum system violate its internal state and make it impossible to obtain information about its other parameters (Heisenberg’s uncertainty principle). In 1980 there appeared the thesis that since modeling the behavior of a quantum system on a classical computer cannot provide sufficient accuracy for reproducing all its parameters, there is a need for a quantum computer. The question arises: to what degree can a quantum computer help to solve traditional epistemological problems of quantum mechanics? Can modelling the behavior of elementary particles on a quantum computer “bypass” the problem of the observer’s influence on the system? In other words, is it possible to obtain information about the behavior of a quantum system without observation? Will the internal state of the simulated system be preserved?

The experimental determination of Th(iv)/Th(iii) redox potentials in organometallic thorium complexes

ThIV/ThIII reduction wave in the cyclic voltammogram of [Th(η-C5H3{SiMe3}2)3Cl].

MODIFIED ELECTRODE FOR NO3- DETERMINATION IN SALINE WATERS BY VOLTAMMETRY METHOD

A certain level of NO3- in water is necessary for the growth of algae. Most aquatic organisms can survive at relatively high nitrate levels, but concentrations higher than 0.2 mg/l cause fish diseases, eutrophication and algal bloom in aquariums. Thus, it is necessary to monitor the level of nitrates in aquarium water. When choosing the method of nitrate level analysis that will be used to develop an in-site saltwater monitor system, we should take into account several key factors, such as the threshold concentration and possible inferences, including high levels of Cl- in saltwater. Other desired criteria for the method are the need to get results in real time, low cost of production, and a way to perform the measurements in-site without the need for highly skilled personnel. The voltammetry was chosen as a method that satisfies our criteria. It is known that nitrate can be reduced quantitatively on a copper electrode. However, the copper electrode becomes poisoned after only a few minutes of use. Previous studies showed that a thin layer of copper deposited on the surface of various commonly used electrodes significantly improve the perfomance of the sensing system. This paper describes the fabrication process of voltammetric sensor and shows the advantage of using a glassy carbon electrode modified with electrodeposited copper layer to measure the concentration of nitrate in sea water. We have found that the modified sensor can be effectively used to catalyze nitrate reduction with a welldefined reduction wave with E= -1.1 V. We performed the cyclic voltammetric (CV) experiments and chose an optimal supporting electrolyte and the optimal conditions for the pretreatment. It was found that the peak current of nitrate increases with the increase of Cl- concentration and is stable in the range (2–3)⋅10-1 mol/l. The pH value from 3.5 to 6.0 does not influence the reaction on an electrode. The developed sensor was used to direct determine of nitrate in artificial seawater without of any sample preparation. Potentiometry with standard proсedure of Cl- precipitation was used to validate all the results. The values obtained by both methods were in good agreement with each other.

Investigation of The Electrode Pathway of Quinoline Azo Dye Compound via Convolutive Voltammetry and Digital Simulation

The electrochemical behavior and the electrode reaction of quinolone azo dye compound was investigated using convolutive cyclic voltammetry at mercury electrode in 50% (v/v) ethanolic Britton-Robinson solutions of pH 2.5 – 12.0. Four electrons slow reduction wave was consumed in acidic and alkaline solutions corresponding to the reduction of the more easily N = N center. A second more cathodic irreversible , pH – dependent, 2-electron wave represents the reduction of quinolone ring. Cyclic voltammetry and convolution transforms were used to determine the kinetic parameters of the electroactive species.The extracted electrochemical parameters were confirmed via digital simulation.Controlled potential coulometry technique was used for calculation the overall number of electrons involved in electrode reaction.