Bidimensional Polyiodide Netting Stabilized by a Cu(II) Macrocyclic Complex

Iodine-dense polyiodide phases are interesting materials for a number of potential uses, including batteries and solid-state conductors. The incorporation of transition metal cations is considered a promising way to enhance the stability, tune the properties, and influence the architecture of polyiodides. However, several interesting metals, including Cu(II), may suffer redox processes, which generally make them not compatible with the I2/I− redox couple. Herein L, a simple derivative of cyclen, is proposed as a Cu(II) ligand capable of protecting the +2 oxidation state of the metal even in the presence of polyiodides. With a step by step approach, we report the crystal structure of free L; then we present spectrophotometric verification of Cu(II) complex stability, stoichiometry, and formation kinetic in DMF solution, together with Cu(II) binding mode elucidation via XRD analysis of [Cu(L)Cl]ClO4∙CH3CN crystals; afterwards, the stability of the CuL complex in the presence of I− is demonstrated in DMF solution, where the formation of a Cu:L:I− ternary complex, rather than reduction to Cu(I), is observed; lastly, polyiodide crystals are prepared, affording the [Cu(L)I]2I3I5 crystal structure. This layered structure is highly peculiar due to its chiral arrangement, opening further perspective for the crystal engineering of polyiodide phases.

Relationship between blood superoxide dismutase activity and zinc, copper, glutathione and metallothioneines concentrations in calves

RedOx processes determine the resistance of the organism to pollutants. The aim of the study was to establish a possible relationship between copper and zinc concentration in the blood of calves and the enzyme activity of superoxide dismutase. The study was conducted in 2019 on 50 calves with a weight of 201-250 kg. The samples of venous blood were taken to estimate the level of hemoglobin, glutathione, metallothioneins, as well as zinc, copper, and superoxide dismutase activity. The obtained average values of these substances concentration were compared between each other. A positive correlation between the activity of superoxide dismutase and the concentration of zinc (r = 0.64) and copper (r = 0.87) in the blood of calves has been established. It may be because both metals are obligatory components of superoxide dismutase. There is also a positive relationship between the levels of copper and zinc (r = 0.68). For the other parameters, no reliable relationship was found. The data obtained indicate a positive relationship between the activity of superoxide dismutase and metal concentrations of copper and zinc in the blood of calves. At the same time, a more significant positive relationship is established for copper.

REDOX PROCESSES IN THE REACTIONS OF N-ARYLSULFONYL-1,4-NAPHTНOQUINONЕIMINES WITH CERTAIN NUCLEOPHILES

Quinone-hydroquinone pairs are prototypes of organic redox systems, and studies of the electrochemical behavior of these compounds are of great interest for research. Electrochemical behavior associated with the equilibrium of electron-proton transfer provides information about the molecular structure and environment of the process. Apart from chemical aspects, quinones play an important role in the biochemistry of living cells. Quinone derivatives, used as drugs for several types of human cancers, have been found to have their biological activity related to their redox behavior. Quinoneimines-aminophenols form similar pairs. In nucleophilic addition reactions of N‑substituted p-quinoneimines, parallel redox processes are often observed, and the higher the redox potential of quinoneimine, the greater the likelihood of such processes. Naphthoquinoneimines with aromatic amines and acylhydrazines follow the scheme of 1,4-addition, but as reaction products are oxidized products -4-arylsulfonylamido‑2-arylamino(2-aroylamino)-1,4-naphthoquinoneimines. The oxidant may be the original naphthoquinoneimine and oxygen. Studies have shown that oxygen in the reaction of 1,4-naphthoquinoneimines with acylhydrazines is the only oxidant that oxidizes the product of 1,4-addition, as evidenced by the study of redox potentials. Both oxidized and reduced form of the compounds, as naphthoquinoneimine and the corresponding aminonaphthol, are used to determine the redox potential by direct potentiometry. Due to the instability of the reduced form in the case of the pair naphthoquinoneimine-aminonaphthol, we used only the reduced form, which is oxidized in the cell by oxygen. The redox potential of the naphthoquinoneimine-aminonaphthol galvanic pair was determined as the average value between the potential Emax, which was established in the system upon complete oxidation of the starting substance, that is, when only naphthoquinone imine remains in the system, and the potential Emin, which was registered at the beginning of the process in the system with the reduced form – the corresponding aminonaphthol. This is the method of direct potentiometry in the variant of the middle potential.

On the Origin of Reversible and Irreversible Reactions in LiNixCo(1-x)/2Mn(1-x)/2O2

Bond formation and breakage is crucial upon energy storage in lithium transition metal oxides (LiMeO2, Me = Ni, Co, Mn), i.e., the conventional cathode materials in Li ion batteries. Near-edge x-ray absorption finestructure spectroscopy (NEXAFS) of the Me L and O K edge performed upon the first discharge of LiNixCo(1-x)/2Mn(1-x)/2O2 (x = 0.33: NCM111, x = 0.6: NCM622, x = 0.8: NCM811) in combination with charge transfer multiplet calculations provide unambiguous experimental evidence that redox reactions in NCMs proceed via a reversible oxidation of Ni associated with the formation of covalent bonds to O neighbors, and not, as widely assumed, via pure cationic or more recently discussed, pure anionic redox processes. Correlating these electronic changes with crystallographic data using operando synchrotron X-ray powder diffraction shows that the amount of ionic Ni limits the reversible capacity - at states of charge where all ionic Ni is oxidized (above 155 mAh/g), the lattice parameters collapse, and irreversible reactions are observed. Yet the covalence of the Ni-O bonds also triggers the electronic structure and thus the operation potential of the cathodes.

Can aluminum, a non-redox metal, alter the thermodynamics of key biological redox processes? The DPPH-QH 2 radical scavenging reaction as a test case.

The increased bioavailability of aluminum has led to a concern about its toxicity on living systems. Among the most important toxic effects, it has been proven that aluminum increases oxidative stress in biological systems, a controversial fact, however, due to its non-redox nature. In the present work, we characterize in detail how aluminum can alter redox equilibriums by analyzing its effects on the thermodynamics of the redox scavenging reaction between DPPH . , a radical compound often used as a reactive oxygen species model, and hydroquinones, a potent natural antioxidant. For the first time, theoretical and experimental redox potentials within aluminum biochemistry are directly compared. Our results fully agree with experimental reduction and oxidation potentials, unequivocally revealing how aluminum alters the spontaneity of the reaction by stabilizing the reduction of DPPH· to DPPH − and promoting a proton transfer to the diazine moiety, leading to the production of a DPPH-H species. The capability of aluminum to modify redox potentials shown here confirms previous experimental findings on the role of aluminum to interfere with free radical scavenging reactions, affecting the natural redox processes of living organisms.