Redistribution Of Electron Density Research Articles

Electronic Structure Engineering of Single-Atom Tungsten on Vacancy-enriched V3S4 Nanosheets for Efficient Hydrogen Evolution.

Constructing single-atom catalysts (SACs) and optimizing the electronic structure between metal atoms and support interactions is deemed one of the most effective strategies for boosting the catalytic kinetics of the hydrogen evolution reaction (HER). Herein, a sulfur vacancy defect trapping strategy is developed to anchor tungsten single atoms onto ultrathin V3S4 nanosheets with a high loading of 25.1wt.%. The obtained W-V3S4 catalyst exhibits a low overpotential of 54mV at 10mA cm-2 and excellent long-term stability in alkaline electrolytes. Density functional theory calculations reveal that the in situ anchoring of W single atoms triggers the delocalization and redistribution of electron density, which effectively accelerates water dissociation and facilitates hydrogen adsorption/desorption, thus enhancing HER activity. This work provides valuable insights into understanding highly active single-atom catalysts for large-scale hydrogen production.

Reevaluation of XPS Pt 4f peak fitting: Ti 3s plasmon peak interference and Pt metallic peak asymmetry in Pt@TiO2 system

The structural, electronic, and electrochemical properties of noble metals supported on transition metal oxides, such as Pt nanoparticles (NPs) supported on TiO2 (Pt@TiO2), have been extensively studied for their relevance to energy technologies, including photocatalysis, electrocatalysis, and electrochemical energy conversion. As the need to lower the amount of Pt and other noble metals used in energy conversion systems becomes urgent, it is essential to accurately quantify the loading of these metals and electronic density redistribution between them and their supports. X-ray photoelectron spectroscopy (XPS) is widely used for the identification and quantification of chemical species. In particular, fitting of the Pt 4f spectra for Pt@TiO2 is frequently performed to determine the chemical environment and oxidation state of Pt, which strongly affect the physical behavior and catalytic performance of this system. Here, we show that neglecting contributions due to the Pt surroundings and the asymmetry of the Pt metal peak in the line shape fitting can lead to severe mischaracterization of the oxidation state of Pt. We quantify the effects of background contributions that stem from the TiO2 support and discuss how factoring in the strong asymmetry of Pt 4f doublets, which stems from the shake-up type processes, affects the interpretation of Pt 4f XPS line shape.

Dataset for carbon dioxide adsorption on lizardite

This paper presents data on the adsorption of CO2 on the (001) and (00 ) surface lizardite. The data were obtained from calculations using the density functional theory (DFT) method implemented in the CASTEP software package. The calculations were performed using the plane wave basis set and the Perdew-Burke-Ernzerhof (PBE) exchange-correlation functional. A semi-empirical Grimme D2 correction was used to correctly account for dispersion interactions, which play an important role in physical adsorption processes. The data include optimized geometry and electronic properties of equilibrium states of adsorbed CO2 on (001) and (00 ) lizardite surfaces. They contain the most energetically favorable adsorption sites and estimates of the interaction strength between the adsorbate and adsorbent. The analysis of the electronic structure includes calculations of charge distribution, density of states (DOS), and visualizations of electron density difference isosurfaces. These data provide detailed insights into the redistribution of electron density during adsorption and the nature of the bonds formed. All data, including optimized crystal structures, electronic properties, and calculation results, are available in formats that can be read by commonly available text editors and specialized atomic structure visualization and analysis software. The presented dataset can serve as a foundation for further studies on the interactions of various molecules with the lizardite surface.

Enhanced Performance for Li & Na Ion Battery Anodes by Charge Modulation of Interface Through SiC4 and SiN1C3 Active Centers on Silicon Nitrogen Co‐Doped Graphene

AbstractHeteroatom doping of graphene is a powerful approach to develop high‐performance Li and Na ion battery anodes. In this study, silicon‐nitrogen co‐doped graphene (Si−N−GN) nanostructures were successfully synthesized via a rational and scalable solvothermal process. The performances of Si−N−GN in Na+ and Li+ half‐cells were investigated in detail by advanced electrochemical techniques and the obtained results were analyzed in terms of Si−N−GN surface properties, reaction kinetics, and electrode/interface interactions. Si−N−GN exhibited a superior capacity of 540 mAh g−1 at a current density of 0.5 A g−1 for Li+ and improved rate capability for both Li+ and Na+ which are linked with the increased interlayer spacing and enlarged graphene sheets upon Si‐doping. Importantly, the capacity increased with the number of cycles owing to surface electron density redistribution and Si−N−GN/SEI interactions, supported by DFT.

Interfacial stability and electronic properties of YBCO/ABO3 heterostructures: A comparative DFT study

In this study, we utilized density functional theory (DFT) to analyze the interfacial properties of YBa2Cu3O7 (YBCO) with perovskite metal oxides LaAlO3 (LAO), KTaO3 (KTO), and SrTiO3 (STO). We focused on surface energies, lattice mismatches, strain energies, and adhesion energies to gauge the stability and compatibility of these interfaces. Our findings indicate that KTO exhibits the highest surface preference due to its lowest surface energy (0.054 eV/Å 2), suggesting superior surface stability. Moreover, LAO and STO show minor lattice mismatches with YBCO, implying effective interface integration, while YBCO/KTO interfaces experience significant strain due to extensive lattice mismatches. STO is distinguished by the lowest strain energy (0.07 eV), indicating minimal energy requirement for lattice mismatch accommodation, unlike KTO, which demonstrates high strain energy (0.42 eV) and potential structural distortions. The strongest interfacial bond, as indicated by an adhesion energy of −2.16 eV, was observed at YBCO/LAO, while the weakest was found at the YBCO/KTO interface, with an adhesion energy of −0.56 eV. Additionally, charge density difference (CDD) analysis highlighted electron density redistribution at the interfaces, predominantly around interfacial oxygen atoms, indicating a mix of ionic and covalent bonding. This study provides comparative insights into the interfacial characteristics of YBCO/ABO3 heterostructures, suggesting pathways for optimizing their design and performance.

Unimolecular net heterolysis of symmetric and homopolar σ-bonds

The unimolecular heterolysis of covalent σ-bonds is integral to many chemical transformations, including SN1-, E1- and 1,2-migration reactions. To a first approximation, the unequal redistribution of electron density during bond heterolysis is governed by the difference in polarity of the two departing bonding partners1–3. This means that if a σ-bond consists of two identical groups (that is, symmetric σ-bonds), its unimolecular fission from the S0, S1, or T1 states only occurs homolytically after thermal or photochemical activation1–7. To force symmetric σ-bonds into heterolytic manifolds, co-activation by bimolecular noncovalent interactions is necessary4. These tactics are only applicable to σ-bond constituents susceptible to such polarizing effects, and often suffer from inefficient chemoselectivity in polyfunctional molecules. Here we report the net heterolysis of symmetric and homopolar σ-bonds (that is, those with similar electronegativity and equal leaving group ability3) by means of stimulated doublet–doublet electron transfer (SDET). As exemplified by Se–Se and C–Se σ-bonds, symmetric and homopolar bonds initially undergo thermal homolysis, followed by photochemically SDET, eventually leading to net heterolysis. Two key factors make this process feasible and synthetically valuable: (1) photoexcitation probably occurs in only one of the incipient radical pair members, thus leading to coincidental symmetry breaking8 and consequently net heterolysis even of symmetric σ-bonds. (2) If non-identical radicals are formed, each radical may be excited at different wavelengths, thus rendering the net heterolysis highly chemospecific and orthogonal to conventional heterolyses. This feature is demonstrated in a series of atypical SN1 reactions, in which selenides show SDET-induced nucleofugalities3 rivalling those of more electronegative halides or diazoniums.

Insight into interfacial engineering for enhancing the synergistic effect of piezo-photocatalytic hydrogen peroxide production

Constructing heterojunctions represents a prevalent approach for enhancing piezo-photocatalytic performance. However, it remains challenging due to contradictory charge polarity and a poor active site. In this study, we employed an in situ hydrothermal method to fabricate a ZnIn2S4-BiOCl compact heterojunction with interfacial chemical bonding. Experimental and theoretical calculations demonstrate that the interfacial chemical bond (Bi-S bond) creates a strong interfacial electronic effect between the heterojunctions, acting as strain centers and charge transfer channels to enhance coordinated piezoelectric and photoelectric fields, thereby facilitating charge transfer. Additionally, interfacial bonding induces dynamic surface reconstruction and redistribution of electron density, improving reactant activation and charge exchange while reducing reaction barriers. Consequently, ZB-4 catalyst exhibits exceptional piezoelectric photocatalytic performance for pure water to H2O2 conversion (1987.33 μmol g-1·h-1), which is 5.85 times than that of pure BiOCl. This study presents a valuable strategy for enhancing positive coordination between heterojunctions and the photocatalytic piezoelectric effect.

Comparative analysis of absorption resonances between carbynes and cyclo [n] carbons

Two approaches are presented here to analyze the absorption resonances between carbynes and cyclo [n] carbons, namely the analytical tight-binding model to calculate the optical selection rules of cumulenic atomic rings and chains and the ab initio time-dependent density functional theory for the optical investigation of polyynic carbon ring and chains. The optical absorption spectra of the carbon ring match that of the finite chain when their eigen energies align following the Nring=2Nchain+2 rule, which states that the number of atoms in an atomic ring Nring is twice the number of atoms on a finite chain Nchain with two additional atoms. Two representative atomic chains are chosen for our numerical calculations, specifically carbynes with N=7and8 carbon atoms as optical resonance spectra match to a recently synthesized carbon ring called cyclo[18]carbon. Despite the mismatch in resonance peaks, molecular orbital transitions of both carbynes N = 7 and 8 and cyclo[18]carbon reveal a wave function symmetry change from inversion to reflection and vice versa for allowed molecular orbital transitions, which results in electron density redistribution along the polyynic carbyne axis or the cyclo[18]carbon circumference. Our investigation of the correlation of optical absorption peaks between carbynes and cyclo [n] carbons is a step towards enhancing the reliability of allotrope identification in advanced molecular device spectroscopy. Moreover, this work could facilitate the non-invasive, rapid and crucial assessment of these sensitive 1D allotropes by providing accurate descriptions of their electronic and optical properties, particularly in controlled synthesis environments.

Spectral Investigations of 60S Bioactive Glass Modified with La and Y Ions.

The changes in the atomic structure and in the network of bonds between oxide tetrahedra in 60S bioactive glass upon modification of its structure by yttrium and lanthanum atoms were investigated via XPS, FTIR, and NMR spectroscopy methods. The presence of nanostructure in the samples of 60S bioactive glass modified with yttrium and lanthanum was demonstrated. The formation of a bioinert core of 60S bioactive glass nanoparticles with the subsequent formation of a biocompatible layer is facilitated by the redistribution of electron density when oxygen bridge bonds are broken, PO4 and SiO4 tetrahedra are fragmented in the polymer matrix, and isolated nanoclusters are formed. Given the fact that during the interaction with the extracellular matrix, the breakdown of covalent bonds -O-Si-O-P- is more energetically costly than the rapid ionic exchange of network modifiers Ca2+ (Y3+, La3+) and the leaching of isolated nanoclusters into the surrounding physiological environment, it is argued that modification of 60S bioactive glass with yttrium or lanthanum can accelerate bioactive ionic processes in the extracellular matrix.

Charge Redistribution in Mechanochemical Reactions for Solid Interfaces.

Mechanochemical strategies are widely used in various fields, ranging from friction and wear to mechanosynthesis, yet how the mechanical stress activates the chemical reactions at the electronic level is still open. We used first-principles density functional theory to study the rule of the stress-modified electronic states in transmitting mechanical energy to trigger chemical responses for different mechanochemical systems. The electron density redistribution among initial, transition, and final configurations is defined to correlate the energy evolution during reactions. We found that stress-induced changes in electron density redistribution are linearly related to activation energy and reaction energy, indicating the transition from mechanical work to chemical reactivity. The correlation coefficient is defined as the term "interface reactivity coefficient" to evaluate the susceptibility of chemical reactivity to mechanical action for material interfaces. The study may shed light on the electronic mechanism of the mechanochemical reactions behind the fundamental model as well as the mechanochemical phenomena.

Breaking hydrogen bond in metal free carbon nitride to induce peroxymonosulfate nonradical activation: Surface-mediated electron transfer

Breaking hydrogen bond in metal free carbon nitride (CN) to increase peroxymonosulfate (PMS) adsorption for surface-mediated electron transfer has been challenging. Herein, we incorporated N−CN monomer into CN to break hydrogen bond by the introduction of polyvinylpyrrolidone (PVP). The developed nonradical oxidation system achieved selective decomposition of highly hydrophilic contaminants and efficient removal of chemical oxygen demand (58.0%), total phosphorus (88.1%), ammonia nitrogen (100.0%) and total nitrogen (67.8%) from the secondary effluent in a continuous flow reactor. This was attributed to that the breakage of hydrogen bond accelerated the redistribution of electron densities at C and N sites, leading to an increase in the adsorption energy of N site to PMS. This promoted the formation of PVP/CN-PMS* complex for the selective and efficient removal of organics and inorganics. This work provided a new perspective for the selective and long-term treatment of practical wastewater.

Microwave construction of the 3D porous interconnected structure of NiCoCr medium-entropy alloy with ultra-high specific capacity for supercapacitors and electrocatalysis

The effective design of bifunctional electrodes with unique morphology and remarkable electrochemical properties for energy conversion and storage devices is a promising but challenging endeavor. Herein, self-supporting NiCoCr medium-entropy alloy (MEA) with a hierarchical porous network structure was in situ synthesized on nickel foam (NiCoCr/NF) by a simple and rapid microwave route. The optimal NiCoCr/NF presented an ultra-high specific capacity of 3011.8 C g−1 (1 A g−1) and outstanding charge/discharge sustainability (83.4% retention at 10 A g−1 over 50,000 cycles) due to its multi-component synergistic effect and hierarchical porous structure. Meanwhile, subtle lattice distortions and electron density redistribution in the NiCoCr MEA tuned electronic structures, resulting in a low overpotential and Tafel slope. Aqueous and solid-state asymmetric supercapacitors were fabricated by using NiCoCr/NF as a cathode and Bi/NF as an anode. The aqueous supercapacitor displayed an exceptional energy density of 314.4 Wh kg−1 at a power density of 800 W kg−1 with 81.8% retention at 10 A g−1 over 20,000 cycles. This study provides a new strategy for the efficient synthesis of electrode materials with interconnected network structures and paves the way for the broader application based on medium-entropy and high-entropy materials as promising candidates for future energy storage devices.

Regulation of electron density redistribution for efficient alkaline hydrogen evolution reaction and overall water splitting

The rational design of morphology and heterogeneous interfaces for non-precious metal electrocatalysts is crucial in electrochemical water decomposition. In this paper, a bifunctional electrocatalyst (Ni/NiFe LDH), which coupling nickel with nickel–iron layer double hydroxide (NiFe LDH), is synthesized on carbon cloth. At current density of 10 mA cm−2, the Ni/NiFe LDH exhibits a low hydrogen evolution reaction (HER) overpotential of only 36 mV due to the accelerated electrolyte penetration, which is caused by superhydrophilic interface. Moreover, an alkaline electrolyzer is formed and provide a current density of 10 mA cm−2 with a voltage of only 1.49 V. It is confirmed by the density functional theory (DFT) that electron from the Ni layer is transferred to NiFe LDH layer, redistributing the local electron density around the heterogeneous phase interface. Thus, the Gibbs free energy for hydrogen adsorption is optimized. This work provides a promising strategy for the rational regulation of electrons at heterogeneous interfaces and the synthesis of flexible electrocatalysts.

Poly(2-hydroxyethyl methacrylate)/BN nanohybride: Enhanced adsorption of antibiotic pollutant removal from wastewater

Increasing wastewater pollution by pharmaceutical waste poses a serious threat to environmental safety and public health, so sorbents with high adsorption capacity and removal efficiency are in high demand. To address this important problem, a novel pellet sorbent containing (2-hydroxyethylmethacrylate)-modified BN nanoparticles (pHEMA/BN) was produced by a combination of CVD synthesis (BN), solution method (pHEMA/BN nanoparticles) and uniaxial pressing (pHEMA/BN pellets) and studied for the adsorption of tetracycline (TC) and linezolid (LNZ) from aqueous solutions. Characterization techniques, including scanning electron microscopy, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy, have provided insight into adsorbent microstructure and specific surface area. At an initial antibiotic concentration of 100 mg/L, pHEMA/BN adsorbent demonstrated an 84–88 % increase in equilibrium adsorption capacity after 24 h and an 86–89 % increase in antibiotic removal efficiency compared to unmodified BN. Molecular dynamics calculations revealed robust interactions between the polymer and BN, accompanied by an electron density redistribution. And density functional theory calculations showed the formation of multiple hydrogen bonds between the polymer hydroxyl groups and the antibiotic functional groups. Adsorption kinetics analysis suggested that pHEMA/BN adsorption involves both physical interaction and chemisorption. The pHEMA/BN material demonstrates good reusability with an adsorption efficiency >90 % after three sorption cycles with sorbent regeneration between cycles. These results highlight the high potential of pHEMA/BN adsorbents for practical applications in drinking water and wastewater treatment, offering versatility and efficiency in the pharmaceutical contaminant adsorption, thereby facilitating the development of more cost-effective and sustainable wastewater treatment methods compared to conventional adsorbents.

Interaction of electrolyte molecules with the surface of porous carbon: NMR study

Electrochemical double-layer capacitors use porous carbons as the electrode material, and improving their performance requires an understanding of the electrolyte−carbon surface interactions. 13C, 14N, and 11B NMR spectroscopy were used to investigate the behaviour of the electrolytes [C(OCH3)3NH3]+Cl- and [N(CH2CH3)]+BF4- on the surface of porous carbon in D2O solutions. A chemical shift of 13C has been found in the fragments N–C, indicating electron density redistribution between nitrogen atoms and alkyl fragments. The presence of a signal with a chemical shift of d = 7.7 confirms the structuring of the electrolytic layer of water solution [N(CH2CH3)]+BF4-.

4a,4b-Dihydrophenanthrene → cis-stilbene photoconversion: TD-DFT/DFT study.

DHP → CS photoconversion was analyzed in terms of electron density redistribution for the first time. The following explanation for the non-recovery of the C4a-C4b bond upon CS relaxation is proposed: during this process, the Coulomb repulsion energy between these pairs of atoms increases by almost one and a half times, and their bonding by an electron at LUMO is insufficient to recover the C4a-C4b bond. According to calculations, upon CS relaxation, the linker connecting the benzene rings undergoes significant structural changes. In this case, the distance between the C4a and C4b atoms increases from 3.00Å to 3.28Å. Calculations showed that the C4a-C4b vibration of the DHP bond has a very low intensity. Therefore, thermal motion does not contribute to the rupture of this bond. All calculations were performed using the Gaussian16 software package at the B3LYP/6-311 + + G(d,p)/IEFPCM theory level. B3LYP was the only hybrid functional supported by Gaussian16, which ensured the cleavage of the C4a-C4b bond of DHP while optimizing its S1 excited state. A quantitative description of the redistribution of electron density in the studied conformers was carried out using the analysis of the NPA of atomic charges. Cyclohexane was used as an implicitly specified non-polar solvent. Visualization of molecular orbitals, and electron densities, as well as plotting of calculated IR spectra, were performed using the Gaussview6 software package.

Excited state dependent fast switching NLO behavior investigation of sp2 hybridized donor crystal as D-π-A push–pull switches

This research focused on the investigating electronic and optical properties of designed chromophores (TPTP1-TPTP5) to involve their comprehensive analysis, including geometry optimization, UV–Vis spectroscopy, analysis of the transition density matrix (TDM), and exploration of their nonlinear optical (NLO) responses. The chromophore TPTP1 and TPTP2 exhibit significant transitions, making them suitable for optical switching applications. The chromophore TPTP5 stood out with high values for linear polarizability (<α0>, 8.53 × 10-24 esu), first order polarizability β0 (3.86 × 10-24 esu), and second order hyperpolarizability (γ0, 6.41 × 10-24 esu), making it notable for its nonlinear optical response. A positive correlation was observed between their vertical ionization potential (VIP) and the γ0 related NLO response, indicating that higher VIP values correspond to stronger γ0 responses. Their UV–Vis spectroscopy was employed to examine the absorption properties of the chromophores, revealing the wavelengths (λmax) at which they absorbed light and their potential for light harvesting applications. The analysis of the TDM allowed for a deeper understanding of the redistribution of electron density during electronic transitions within the chromophores. This analysis provided valuable insights into the characteristics and nature of their excited states. Additionally, the research investigated the NLO responses of the chromophores, particularly focusing on their third harmonic generation (THG) properties. These NLO properties are crucial for potential applications in optical switches, frequency conversion, and optical signal processing. Overall, the findings from this research contribute to a comprehensive understanding of the electronic and optical properties of the designed chromophores. The obtained results open up new possibilities for their utilization in various technological fields, including light harvesting, photonics, and nonlinear optics.

Self‐Assembled 3D N/P/S‐Tridoped Carbon Nanoflower with Highly Branched Carbon Nanotubes as Efficient Bifunctional Oxygen Electrocatalyst Toward High‐Performance Rechargeable Zn‐Air Batteries

AbstractHeteroatom doping and 3D nanostructures with large specific surface area and hierarchical porous structure can synergically improve oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). In this study, the 3D N/P/S‐tridoped nanoflower with highly branched carbon nanotubes bifunctional catalyst (Co/SP‐NC) is prepared by a simple self‐assembly pyrolysis method. The powerful driving force of coordination interaction of ammonium ion can promote the self‐assembly of 2D ZnCo‐ZIF nanosheets into 3D ZnCo/S‐ZIF nanoflowers at room temperature stirring. The 3D ZnCo/S‐ZIF nanoflower surface is driven by sodium hypophosphite to form highly branched carbon nanotubes during the pyrolysis process. Moreover, Density functional theory (DFT) calculations also confirm that the simultaneous introduction of N/P/S can promote the redistribution of electron density at the catalyst interface. The proper P‐doping not only enhances the electronic conductivity of the substrate, but also facilitates the charge transfer in the OER/ORR process. Therefore, Co/SP‐NC cathode assembled zinc‐air batteries (ZABs) have a higher power density (187 mW cm−2), a larger specific capacity (801 mAh gZn−1) and excellent cycle stability compared to Pt/C‐RuO2 assembled ZABs. This work will pave the way to regulate the components interactions by designing 3D hierarchical porous structures.

Electrochemical Analysis in Charge-Transfer Science: Polarity at Electrode Surfaces Affect Electrochemical Analyses for Charge-Transfer Systems

Electrochemical analysis is a vital component of the science of charge transfer (CT), and its importance cannot be overstated. Many fields, including energy science, photoredox and electrocatalysis, biomedical sensor development, environmental engineering, and electronics, rely heavily on CT and require accurate electrochemistry. [Phys. Chem. Chem. Phys. 2020, 22, 21583-21629] As a result, it is critical to pay close attention to the details of collecting, implementing, and interpreting electrochemical results to advance this broad field of science and engineering. [Current Opinion in Electrochemistry 2022, 31, 100862]The interfaces of an electrochemical cell present specific challenges for the interpretation and applicability of the analysis. The polarity of the medium on the electrode surface is not the same as the polarity of the bulk medium, and this has a significant influence on the behavior of charged and dipole species. Solvation in a condensed medium controls the dynamics of processes involving CT, including intramolecular redistribution of electron density. Polarity affects several properties of solvated species, including solubility, reactivity, electrochemical potential, and spectral transitions. [J. Phys. Chem. B 2023, 127, 6, 1443–1458]To understand changes in electrochemical potential during oxidation and reduction, it is important to analyze the relationship between the bulk electrolyte concentration and the Born microenvironmental polarity experienced by the species analyzed in the diffuse Helmholtz layer and at the surface of the working electrode during the heterogeneous steps of CT. This analysis can be used to assess the polarity experienced by redox species on the surface of polarizing working electrodes.Another critical issue in electrochemical analysis is the liquid junction that connects two different solutions, typically through a porous medium. Differences in the transport properties and activity of ions on both sides of the junction create a potential, known as the liquid potential (ELJ), which contributes to the measured voltage. To minimize ELJs, a miscible solvent solution and an electrolyte composed of ions with the same mobility throughout the transition can be used. ELJs can also be eliminated using a cell configuration with a pseudo-reference electrode that does not contain a liquid interface. However, the potential of pseudo-reference electrodes depends on the composition of the sample solution in which they are immersed, so care must be taken when interpreting the measured values.Overall, electrochemical analysis is a complex and critical part of CT science, and its accurate implementation is essential in advancing this broad field of science and engineering. Understanding the influence of the polarity of the medium, the relationship between the bulk electrolyte concentration and the Born microenvironmental polarity, and the liquid junction is crucial for interpreting electrochemical results and evaluating CT thermodynamics.

Interaction of magnesium ions with semiquinone radicals of tiron used as an indicator of reactive oxygen species

Electron paramagnetic resonance spectroscopy (EPR) and quantum chemical calculations based on density functional theory were used to demonstrate that the earlier observed changes in the EPR spectra of Tiron semiquinone radical dissolved in sea water solution occur due to interaction of Mg2+ ions with Tiron radical. This interaction is caused by electrostatic attraction between Mg2+ ions and Tiron radicals, which bears great charges of opposite sign (+2 and -3), on the one hand, and due to the ability of Mg2+ ion to bind to bidentate oxygen-containing ligands efficiently, on the other hand. The formation of tight contact ion pairs leads to electron and spin density redistribution in the Tiron radical, as can been seen by the observed changes in the EPR spectra of the radical.