Behavior Of Electrolytes Research Articles

Understanding Redox Organic Behavior in Deep Eutectic Solvents: Considerations for Molecular Design

Abstract Electrolytes based on deep eutectic solvents (DESs) coupled with redox active organic molecules have shown potential as a versatile and energy dense electrochemical energy storage system. However, progress in these systems has been held back by a lack of understanding of the irregular behavior displayed when redox active organic molecules are transitioned from other solvent systems. In this work, the hydrogen bonding characteristics of a series of redox organic molecules were investigated through infrared spectroscopy and molecular modeling. New understanding of these interactions was then used to explain their electrochemical behavior in a DES electrolyte. A model was used to predict the behavior of new derivatives towards the design of an optimized redox organic-DES system. Hydrogen bonding between the redox molecules and the solvent was found to significantly shift the potential of a redox reaction more positive when a hydrogen bond forms at the redox active site. It was predicted that functionalizing a molecule with electron withdrawing groups to lower the electron density of the redox active functional group lowers the strength of the hydrogen bond and thus alleviates the undesirable potential shift. This hypothesis was demonstrated by the addition of nitro groups to fluorenones.

Synergistic Electrode and Electrolyte Polarities Lead to Outstanding Organic Potassium‐based Batteries

AbstractOrganic materials are promising as battery electrodes due to their flexible design, low cost, and sustainability. Although high electrolyte concentrations are known to suppress organic cathode dissolution, the organic cathode solubility depends on the interplay between the electrode and electrolyte polarities, which remains unexplored. Here, we elucidate the delicate interplay of electrode and electrolyte polarities to achieve stable cycling of organic cathode. Notably, we demonstrate that the solubility of low‐polar organic cathodes initially increases and subsequently decreases in electrolytes with increasing polarity. In contrast, high‐polar organic cathodes display increasing solubility in electrolytes with increasing polarity. When the polarities of the organic cathodes and the electrolyte are tuned, the batteries show high‐capacity retention and Coulombic efficiency. For example, polyaniline||potassiated graphite (KC8) pouch cells deliver 2500 cycles with an average Coulombic efficiency of 99.85 %. These new insights into low‐ and high‐polar organic cathode behavior in electrolytes lay a theoretical foundation for designing new organic battery electrodes and optimizing their electrolyte formulation.

Synergistic Electrode and Electrolyte Polarities Lead to Outstanding Organic Potassium-based Batteries.

Organic materials are promising as battery electrodes due to their flexible design, low cost, and sustainability. Although high electrolyte concentrations are known to suppress organic cathode dissolution, the organic cathode solubility depends on the interplay between the electrode and electrolyte polarities, which remains unexplored. Here, we elucidate the delicate interplay of electrode and electrolyte polarities to achieve stable cycling of organic cathode. Notably, we demonstrate that the solubility of low-polar organic cathodes initially increases and subsequently decreases in electrolytes with increasing polarity. In contrast, high-polar organic cathodes display increasing solubility in electrolytes with increasing polarity. When the polarities of the organic cathodes and the electrolyte are tuned, the batteries show high-capacity retention and Coulombic efficiency. For example, polyaniline||potassiated graphite (KC8) pouch cells deliver 2500 cycles with an average Coulombic efficiency of 99.85%. These new insights into low- and high-polar organic cathode behavior in electrolytes lay a theoretical foundation for designing new organic battery electrodes and optimizing their electrolyte formulation.

Enhanced Ion Solvation and Conductivity in Lithium-Ion Electrolytes via Tailored EMC-TMS Solvent Mixtures: A Molecular Dynamics Study.

The development of stable, high-performance electrolytes is essential to addressing the safety concerns and limited lifespan caused by the thermal and chemical instability of traditional organic carbonate-based electrolytes in lithium-ion batteries (LIBs). This study examined the potential of mixed solvent systems, specifically ethyl methyl carbonate (EMC) and tetramethylene sulfone (TMS), to modify ion solvation and improve ionic conductivity in LIB electrolytes. Through molecular dynamics simulations, we investigated the solvation structure and transport properties of lithium ions (Li+) in these solvent environments. The inclusion of TMS altered the solvation structure, with TMS molecules preferentially coordinating with Li+ ions, displacing PF6 - anions and reducing their electrostatic interference. Our results demonstrated a synergistic interaction between EMC and TMS, where an EMC/TMS ratio of 1:2 led to a significant improvement in ionic conductivity, reaching 0.91 mS/cm, with a corresponding Li+ transference number of 0.40. These findings provide key insights into the molecular-level interaction governing electrolyte behavior, offering guidance for the design of future solvent mixtures to improve the safety and efficiency of LIBs.

Application of Chitosan and the Green Synthesized NiO-Bi2O3 Nanocomposite in Modification of Glassy Carbon Electrode for Simultaneous Determination of p-Nitrophenol and o-Nitrophenol

A solventless method was used to prepare NiO nanoparticles (NPs) while an aqueous extract from banana peels was used to green synthesize Bi2O3 NPs. Characterization of the resulting samples indicated the formation of pure mesoporous NiO and Bi2O3 NPs with crystallite sizes of 23 and 3.1 nm, respectively. A glassy carbon electrode (GCE) was modified by applying chitosan (CS) along with NiO and Bi2O3 NPs. The fabricated NiO-Bi2O3/CS/GCE sensor was applied for the simultaneous determination of p-nitrophenol (p-NP) and o-nitrophenol (o-NP) using cyclic, linear sweep, and differential pulse voltammetry. p-NP showed excellent behavior in PBS electrolyte at pH 7.0 and a 100 mV/s scan rate. The calculated limits of detection and quantitation and linear range were 23.8, 79.5, and 0.1–100 nM, respectively. The sensor demonstrated high selectivity (less than 5% change in the presence of various interferences), reproducibility (2.43% RSD), and stability (98.35% after one month). Finally, the sensor had successfully estimated p-NP in tap and wastewater samples.

In Situ Characterization of the Oxidation Behavior of Carbonate-Based Electrolytes for Lithium-Ion Batteries by Scanning Electrochemical Microscopy

In Situ Characterization of the Oxidation Behavior of Carbonate-Based Electrolytes for Lithium-Ion Batteries by Scanning Electrochemical Microscopy

Ionic Conductivity and Viscosity Behavior of PMMA-based Nano-dispersed Polymer Gel Electrolytes Containing Lithium Perchlorate

Abstract: In this study, nano-dispersed polymer gel electrolytes containing polymethylmethacrylate (PMMA), lithium perchlorate (LiClO4), diethyl carbonate (DEC), dimethylacetamide (DMA), and nano-sized fumed silica (SiO2) have been synthesized and characterized. The electrolytes showed high ionic conductivity for electrolytes with higher dielectric constant solvents. The polymer enhanced the ionic conductivity of liquid electrolytes having a lower dielectric constant solvent (DEC) at all PMMA concentrations than the electrolytes containing a high dielectric constant solvent (DMA). Further, with the addition of nano-sized fumed silica, the ionic conductivity showed a small increase along with an increase in the mechanical stability of the electrolytes. The viscosity behavior of the electrolytes was also discussed, and it was correlated with the results of the ionic conductivity test. Nano-dispersed polymer gel electrolytes exhibited high ionic conductivity (10-2 S/cm). Further, the conductivity showed only a small change (by a factor, not by an order) over the 25-100°C temperature range and did not vary with time, which is desirable for their use in practical applications.

Electrified Nanogaps under an AC Field: A Molecular Dynamics Study.

The organization and dynamics of ions and water molecules at electrified solid-liquid interfaces are generally well understood under static fields, especially for macroscopic electrochemical systems. In contrast, studies involving alternating (AC) fields tend to be more challenging. In nanoscale systems, added complexity can arise from interfacial interactions and the need to consider ions and molecules explicitly. Here we use molecular dynamics (MD) simulations to investigate the behavior of NaCl aqueous solutions at different concentrations confined in nanogaps under AC fields ranging from 10 MHz to 10 GHz. We explore the impact of the gap size (2-60 nm) and of the solid material composing the electrode (silica, charged silica, or gold). Analysis of the transient and stable responses of the system shows that the total transverse dipole M z,total formed by the water molecules and the ions across the gap is always able to counter the applied field regardless of AC frequency, NaCl concentration, or electrode material. As expected, the ions lag at higher frequencies, leading to a capacitive behavior. This effect is fully compensated by water dipoles that lead the field, reaching a maximum lead at a specific frequency which depends on salt concentration and gap size. Changing the gap size affects the magnitude of M z,total. Finally, the electrode material is shown to affect the electrolyte behavior in the gap region. We anticipate these results to be useful for nanoscale dielectric spectroscopy, including scanning probes.

Thermodynamic and Mass Transport Characterization of Lithium Hexafluorophosphate in Dimethyl Carbonate

This research provides a comprehensive analysis of the thermodynamic and transport properties of lithium hexafluorophosphate (LiPF6) in dimethyl carbonate (DMC), which are critical for the performance of lithium-ion batteries. We employed advanced techniques to precisely quantify density fluctuations, which we then systematically correlated with changes in salt concentration and temperature. This intricate relationship was explicated using a data fitting model, conforming to the tenets of Debye–Hückel theory. Through the application of concentrated-solution theory, our study explores the electrolyte's behavior by assessing three key transport properties: cation transference number, ionic conductivity, and thermodynamic diffusivity. This investigation helps elucidate the interactions between different species. Additionally, we describe three thermodynamic characteristics of the electrolyte's equilibrium: the thermodynamic factor, and the partial molar volumes for both the salt and the solvent. The findings offer a detailed insight into the dynamics of the electrolyte, establishing a foundation for improving electrolyte formulations in increasingly complex and concentrated systems.

The Influence of Fluoroalkyl Group in Alcohol on the Interaction between Alcohols and Fluoride Ion

Fluoride ion combined with large cations shows high basicity and reactivity. Taming F− with a hydrogen bonding donor such as an alcohol can moderate its basicity, sometimes enabling its effective use in chemical and electrochemical reactions.[1][2] Alkali metal fluoride−alcohol systems are interesting candidates because of its high solubility of F−, basicity, and chemical and electrochemical stability, and simple preparation. This study focuses on CsF−IP (2-propanol) and CsF−HFIP (1,1,1,3,3,3-hexafluoro-2-propanol) systems. Electrochemical behavior of HFIP-based electrolytes was investigated recently owing to its high oxidative stability.[3][4] In this study, the structural and physical properties of the CsF−HFIP and CsF−IP systems were comparatively discussed. The interaction energy calculations revealed that the interaction between HFIP and F− is stronger than that between IP and F−, which involves the conformational change of HFIP. The peak shift in IR and 1H NMR spectra and the decrease in activity coefficient of alcohols upon the addition of CsF also identified the strong OH∙∙∙F− interaction in the CsF−HFIP system. All these observations suggested that introduction of fluoroalkyl group to an alcohol strengthens the interaction between the OH and F−, which facilitates the dissociation of the cation and anion and enhances the ionic conductivity as also indicated by the diffusion coefficient measurements. On the other hand, IP can also dissolve CsF to a high concentration but the cation and anion highly associate in the solution without giving a sufficient number of conductive species compared to CsF−HFIP system.

Beneficial Impact of Selenate/Selenide Additives on the Performance and Longevity of the Iron Electrode for Alkaline Batteries

The alkaline iron electrode stands out as a cost-effective and robust negative electrode option, particularly suited for large-scale energy storage applications. During discharge, iron undergoes oxidation transforming into iron dihydroxide (Fe(OH)2). Iron dihydroxide is insulating in nature which inhibits electrode discharge. The iron sulfide (FeS) is introduced as an additive to the iron electrode which serves to establish a conductive matrix, facilitating electrode discharge. However, the longevity of iron electrodes is constrained by the iron sulfide (FeS) additive. Through repeated cycles of charge and discharge, the sulfide ions gradually deplete from the electrode, undergoing slow dissolution and irreversible oxidation to sulfate. We have investigated alternative additives to iron sulfide, with iron selenide (FeSe) emerging as a promising candidate. Experimental findings reveal that iron selenide offers comparable benefits to sulfides while exhibiting reversible oxidation and reduction. Through extensive electrochemical investigations of selenate/selenide behavior in alkaline electrolytes and repeated cycling of battery electrodes, we demonstrate the superior longevity of iron selenide over iron sulfide additives. Our results indicate a remarkable 96% capacity retention in iron electrodes containing FeSe additives up to the 1450th cycle, as shown in Figure. Figure 1

Comprehensive Study on the Role of Proton in the Insertion Chemistry of Aqueous Zn-Ion Batteries

Li-ion rechargeable batteries played a major role in the present revolution of portable devices since Goodenough's group switched from sulfide to oxide cathode materials in the 1980s. However, the safety of explosive organic electrolytes, rising demand-driven costs, and even geopolitical concerns over lithium minerals have prompted scientists to seek alternate systems. Due to their enormous capacity, Zn-ion rechargeable batteries with a non-explosive aqueous electrolyte have garnered significant attention among the candidates. Especially the newly demonstrated capacity over 300 mAh/g in the V2O5 cathode illustrated the promise of the aqueous Zn-ion system. Although aqueous electrolytes reduce safety concerns, how protons function in insertion chemistry is still unclear. In contrast to Li-ion's single insertion behavior in organic electrolytes, charge carriers compete with one another, particularly in low-pH regions with a lot of proton content. Therefore, a thorough examination of insertion behavior over a broad pH range is necessary to comprehend the involvement of protons.In this work, we systematically investigated the insertion behavior in the V2O5 cathode in two distinct cell types in three pH conditions. To guarantee reliable results, we integrated multi-scale analytical methods and selected compact sampling points from discharge curves. Our first cell type, the beaker cell, provided sufficient protons comparable to metal cations. The insertion behavior in this environment was dependent on the proton concentration. EDS Elemental maps from samples with greater pH levels reveal Zn signals are found even in the early stages of discharge, despite the fact that protons are inserted first in low-pH samples (Fig. 1a). This implies that Zn-ion plays a major role as a charge carrier while influence of protons on discharge voltage or capacity becomes less significant under mildly acidic conditions. Additionally, the vanadium’s valence state changed as the discharge proceed, more reduced when Zn-ion is inserted instead of proton in the high-pH region, according to the XPS spectrum from identical samples with EDS maps. We employed X-ray absorption spectroscopy techniques to overcome the shortcomings of the surface sensitivity of XPS and local region observation in STEM. The XAS results provided insights about the overall oxidation state changes of vanadium as a result of carrier-ion insertion, where the XANES spectrum shows a modest reduction with proton insertion and a notable reduction upon the Zn-ion insertion. The bonding nature was further explained by the simultaneously obtained EXAFS spectrum, which showed the characteristic peak of the Zn insertion site and the peak splitting of V-V bonding under high pH circumstances. In addition to Zn-ion electrolytes, we also revealed similar pH-dependent insertion behavior in monovalent Na-, divalent Mg-, and trivalent Al-ion electrolytes to generalize our hypothesis.Coin cell cases show the opposite of the beaker cell test, where the proton has a negligible effect on the insertion chemistry. Regardless of proton concentration, we discovered that Zn-ions are always inserted from the first step of discharge, as evidenced by elemental maps in Fig. 1b. The oxidation state variation of vanadium in the XPS spectrum and even redox peak position in CV curves for every pH was identical, which can be somewhat inferred from similar discharge curve shapes irrespective of pH. We concluded that the proton contribution to discharge capacity is only meaningful when a substantial amount of highly acidic electrolyte is supplied. Thus, it is essential to consider the relative mass ratio between the electrolyte volume and cathode material mass to ascertain how protons affect the voltage and capacity of an aqueous battery system. Figure 1

Electrolyte Li⁺ Chemical Potential as a Descriptor of Li+ Intercalation Behavior of Graphite Negative Electrodes

Introduction Better electrolytes are being extensively explored to improve the performance and safety of lithium-ion batteries. One of the challenges in developing new electrolytes is to avoid the co-intercalation of lithium ions (Li⁺) and solvents into graphite negative electrodes during charging. In this reaction, solvated Li⁺ intercalates between the graphite layers without de-solvation, leading to lower capacities and poor reversibility. Previous works showed that the solvent co-intercalation could be suppressed by employing highly concentrated electrolytes1,2, weakly coordinating solvents3, or adopting proper co-solvents.1 However, a quantitative and experimental factor that dominates the Li⁺ intercalation behavior has yet to be identified. In this study, we focused on Li+ chemical potential (μ Li⁺) in electrolytes as a novel descriptor. We show how the μ Li⁺ is related to the Li⁺ intercalation behavior at graphite electrodes. Experimental Electrolytes with various concentrations of lithium bis(fluorosulfonyl)imide (LiFSI) were prepared using 1,2-dimethoxyethane (DME), 1,2-diethoxyethane (DEE), or dimethyl sulfoxide (DMSO), all of which easily co-intercalate into graphite electrodes. Li⁺ intercalation behavior was categorized as follows: only Li+ intercalates into graphite (noted as Li-GIC), both Li+ and solvated Li⁺ intercalates into graphite (noted as incomplete Li-GIC), and solvated Li⁺ intercalates into graphite (noted as Li-solv-GIC). The Li⁺ intercalation behavior was judged from charge-discharge curves observed in graphite|Li coin cells. To quantify the μ Li⁺, we used lithium electrode potential (E Li) with reference to the redox potential of ferrocene (Fc/Fc+) using a previously reported method by our group.4 Results and discussion E Li (and μ Li⁺) and Li⁺ intercalation behavior in various electrolytes. In all electrolytes, the E Li (and μ Li⁺) increased with increasing salt concentration, which is consistent with the previous study.4 We found that the Li⁺ intercalation behavior depended on the E Li (and μ Li⁺); solvent co-intercalation was mainly observed in the electrolytes with E Li < -3.25 V vs. Fc/Fc+, whereas only Li⁺ tended to intercalate into graphite by suppressing solvent co-intercalation in electrolytes with E Li > -3.25 V vs. Fc/Fc+. Therefore, the obtained trend suggests that μ Li⁺ could be a quantitative descriptor of the Li⁺ intercalation behavior at graphite electrodes. Acknowledgment A part of this study was supported by JSPS KAKENHI Grant-in-Aid for Transformative Research Areas (B) (23H03824, 23H03827). Reference (1) Yamada, Y. et al., J. Phys. Chem. C, 114, 11680–11685 (2010). (2) Yamada, Y. et al. ACS Appl. Mater. Interfaces, 6, 10892–10899 (2014). (3) Li, Z. et al., J. Mater. Chem. A, 11, 19996–20010 (2023). (4) Ko, S. et al., Nat. Energy, 7, 1217-1224 (2022) Figure 1

An Integrated Experimental-Theoretical Study on the Role of Additives in the Acid Electrodeposition of Copper

Copper electroplating plays a critical role in the field of industrial processes. Copper is among the most common electrodeposited layers in both technological and decorative applications. Moreover, copper electroplating is a key step to avoid nickel layers, in fact, there is a growing trend toward Ni-free production process due to concerns about the toxicity of Ni [1,2].Common copper electroplating solutions typically consist of CuSO4, H2SO4, NaCl, and different organic additives named suppressor, brightener, and leveller [3,4]. These types of additives are crucial for achieving shiny and adherent deposits but despite their widespread use, the mechanisms of action remain unclear. Understanding the influence of additives is important both to improve the quality of deposits and to meet environmental sustainability goals, including reducing organic pollutants in wastewater and replacing toxic additives like thiourea with eco-friendly alternatives such as L-cysteine. In this context, a comprehensive analysis using an integrated experimental and theoretical approach can provide significant benefits.In this study, Electrochemical techniques and computational methods were used to elucidate the mechanisms behind the use of additives in industrial copper electroplating. Classical molecular dynamics simulations, following the gaff2016 protocol, were performed to study the behaviour of electrolytes under an electric field and assess the possibility of physical absorption. Additionally, ab-initio calculations using CAM-B3LYP(D3BJ) and a mixed 6-31G(d,p)-LANL2DZ basis set were employed to investigate the possibility of a chemical absorption and explain how additives influence the directional growth of copper nuclei.The theoretical results obtained were verified experimentally by performing electrochemical depositions of copper under different conditions. X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy were used to study the surface composition and provided information on the nature of adsorption (chemical or physical) of additives on the copper surface. Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM) were used to investigate the effect of additives on the morphology of the deposits, including grain size and roughness. Finally, X-ray diffractometry (XRD), SEM, and AFM imaging helped quantify preferential orientation caused by additives and revealed the influence in the initial growth steps, identifying a pivotal 2D structure. The innovatively interdisciplinary approach based on the integration of experimental and theoretical used in this work made the understanding of electrodeposition processes more clear, paving the way for sustainable and efficient electrochemical manufacturing practices.

Polymer Electrolytes with High Ionic Conductivities at Freezing Temperature for Aqueous Hybrid Batteries.

Rechargeable and flexible aqueous batteries (ABs) have emerged as one of promising energy devices which is primarily due to the safety, environmental friendliness and economic efficiency. However, because of the freezing behavior of aqueous electrolytes, most ABs possess poor performance when the working temperature drops below zero. To solve this problem, a gel polymer electrolyte (GPE) with high ionic conductivity (IC) and frost-resistance is designed for aqueous Zn-Li hybrid batteries by a biomass-based polymers complex consisting of carboxyl modified sodium alginate (SA) and zwitterionic betaine (BA). Introducing iminodiacetic acid to enrich -COOH groups along the SA main chains could improve IC of the prepared GPEs to 41.27 and 20.96 mS cm-1 at 20 and -20 °C, respectively. At -20 °C, the discharge capacity of the resultant cell is two times higher than that of the liquid electrolyte-based cell, and the cell presents a capacity retention of 91.6 % after 300 charge/discharge cycles at 1 C. This proposed strategy greatly improve the IC of GPEs at freezing temperature, which is expected to broaden the practical application of GPEs in wide range of temperature.

Pectin alignment induced changes in ion solvation structure in ethylene carbonate-based liquid electrolytes

Classical molecular dynamics simulations are used to explore the impact of the alignment of pectin over the randomized configuration on ion solvation structure in pectin-loaded ethylene carbonate - lithium bis(trifluoromethanesulfonyl) imide electrolytes. Our study focuses on how biological macromolecules, specifically pectin, influence the behavior of liquid electrolytes, considering their applications in rechargeable batteries due to their ion solvation capabilities and ion transport characteristics. Aligned pectin causes a tightly packed first coordination shell of anions around lithium ions by weakening the long-ranged interactions beyond the first coordination shell compared to a random configuration. Consequently, the number of pectin oxygens around lithium decreases dramatically from 3 to 2, resulting in an overall diluted solvation shell containing fewer numbers of anions and pectin oxygens around lithium ions. With polymer alignment, the non-Gaussianity increases from 3.387 to 6.550 for lithium ions and from 0.475 to 0.621 for TFSI ions, reflecting a 90% increase in dynamic heterogeneity for lithium ions and a 30% increase for TFSI ions. Cation-cation correlations enhance ionic conductivity in randomized pectin, whereas isolated anion motion dominates in aligned pectin due to cation-pectin interactions. Our work not only highlights potential strategies for improving electrolyte performance in rechargeable batteries but also emphasizes the crucial role of molecular orientation in optimizing electrolyte properties, paving the way for more optimized and efficient battery technologies.

Anodic Dissolution Behavior of DD6 Nickel-Based Single Crystal Superalloy for Electrochemical Machining Applications

Nickel-based single crystal superalloys have been widely used in turbomachinery components. Electrochemical machining (ECM) is an essential method for shaping such high-performance alloys. Understanding the fundamentals of ECM for these alloys is crucial for the design and optimization of the process. This study investigated the anodic dissolution of DD6 nickel-based single crystal superalloy in concentrated NaCl and NaNO3 electrolytes under ECM conditions. Polarization curves showed a passive-transpassive transition behavior in both electrolytes. Galvanostatic experiments demonstrated unique current efficiency characteristics contradicting the empirical ECM knowledge. Surface analysis revealed that the anomalous current efficiency of &gt;100% in the NaNO3 electrolyte results from the falling of γ' phases from anodic surfaces due to the preferential dissolution of the γ matrix phase. The transition from selective to uniform dissolution with increased current density and reduced electrolyte flow velocity leads to decreased current efficiency in NaNO3 electrolyte. The removal of both γ and γ' phases depends entirely on electrochemical dissolution in NaCl electrolyte, ensuring that current efficiency maintains a normal value. A schematical anodic interface model was proposed to describe the dissolution behavior.

Corrosion behavior of magnesium-aluminum spinel in low-temperature electrolytes

Magnesium-aluminum spinel composite is a novel material designed for low-temperature aluminum electrolytic baths without a ledge profile. In this study, multi-doped magnesium-aluminum spinel was successfully prepared, and its corrosion behavior in low-temperature aluminum electrolytes was investigated. The multi-doped magnesium-aluminum spinel exhibited high relative density and homogeneous grain structure. The addition of lithium fluoride and potassium fluoride altered the physical structure of the aluminum electrolytes. A corundum phase was observed on the surface of the corroded multi-doped magnesium-aluminum spinel. The average corrosion depth and static corrosion rate were found to be related to the electrolyte composition and liquidus temperature. Notably, the corrosion rate decreased as the exposure time increased.

Synthesis, and spectroscopic characterizations of gold(III) complexes containing nitrogen-heterocycle based pyridine derivatives as a biomolecular chelates

Three gold(III) nanostructured complexes of nicotinamide (nta), picolinic acid (pica), and isonicotinic acid (inta) were synthesized by the reacted of AuCl3 salt with nta, pica, and inta with 1:2 stoichiometry in the alcoholic medium. The solid products obtained were formulated by comparing experimental and calculated data for microanalytical (C, H, N) and metal. Both produce 1:2 compounds with metal ions. The prepared complexes were characterized by different physico-spectroscopic techniques. The FTIR, and 1H NMR spectral analysis, morphological analysis (scanning electron microscopy SEM, transmittance TEM, and X-ray powder diffraction XRD) of these complexes have been discussed. The conductive behavior of the complexes indicates that all of them behave as electrolytic behavior. The mononuclear gold(III) complexes have formulated as [Au(nta)2(Cl)2].Cl, [Au(pica)2].Cl and [Au(inta)2].Cl. The shifts of the ν(N–H) amino, ν(C=N) pyridine, and ν(C=O) carboxylic stretches have been monitored to find out the donor sites of the ligands. According to the experimental data, the three complexes can be characterized in the solid state as mononuclear, with a four-coordinate stereochemistry. KEY WORDS: Gold complex, Nicotinamide, Picolinic acid, Isonicotinic acid, Nanostructure, Spectroscopic Bull. Chem. Soc. Ethiop. 2025, 39(1), 111-121. DOI: https://dx.doi.org/10.4314/bcse.v39i1.9

Divalent transition metal complexes with mixed of β-enaminone and N,O-donor ligands: synthesis, characterization and biological assessment

This study extensively describes the synthesizing and characterizing of new β-enaminone complexes derived from dimedone and amines coordinated with transition metals Fe(II), Co(II), Ni(II), and Cu(II), also two ligand's metformin (Met) and 8-hydroxyquinoline (8-hq). These were determined via FT-IR, 1H-NMR, electron and mass spectroscopy, molar electrical conductivity, thermal analysis (TGA, DTA and DSC) and characterized by metal content determination (%), magnetic susceptibility and elemental analysis (C.H.N.) and SEM technique. The measurements indicate that the complexes have six coordination numbers, where the β-enaminone is coordinated as tetradentate ligand through the two nitrogen atoms and the two oxygen atoms beside metformin is coordinated through the two nitrogen atoms and 8-hydroxyquinoline is coordinated by oxygen and nitrogen atoms as bidentate ligands. The conductance suggests that all complexes have electrolytic behavior, being conductive in a ratio of (1:2). SEM results revealed the presence of nanostructures on sample surfaces. The biological activity of the prepared ligands and complexes are studied in different concentrations for four types of bacteria Staphylococcus aureus has (+G) and Escherichia coli, Pseudomonas aeruginosa, Klebsiella have (-G), well as, the influence of the fungus. The ligands have disparate effectiveness while complexes have high effectiveness inhibiting the bacteria and fungus. KEY WORDS: Mixed ligand systems, Dimedone, β-Enaminone ligands, Transition metals, Biological application Bull. Chem. Soc. Ethiop. 2025, 39(1), 65-78. DOI: https://dx.doi.org/10.4314/bcse.v39i1.5