Cationic Forms Research Articles

Computational Insights Into Betanin for Dsscs: Unraveling Deprotonation Variations and Identifying Optimal Anchoring Sites on TiO2

AbstractBetanin (Bn), a natural dye in the Betalains family, predominantly takes on a cationic form known as Bn+. However, it exists in a neutral state as Bn_C2, Bn_C15, and Bn_C17 by losing an H+ from one of its carboxylic acids. Density functional theory (DFT) and Time‐dependent density functional theory (TD‐DFT) studies evaluate the efficiency of each betanin form and pinpoint the most probable anchoring point to TiO2. The Bn_C17 variant stands out as a highly promising candidate for DSSC cells, demonstrating a distinctive combination of electron injection efficiency, electrochemical performance, hole transport capabilities, and photovoltaic behavior. Considering factors like adsorption energy, binding mode, structural compatibility, electronic properties, and absorption characteristics, Bn_C17@TiO2 emerges as the most favorable dye@TiO2 complex among the studied betanin forms for DSSC applications. Contrastingly, the C2‐COOH anchoring point presents challenges with monodentate binding, a different orientation, and potential load distribution issues. This behavior, resembling that of a p‐type dye, differs from the n‐type behavior exhibited by the C15‐COOH and C17‐COOH forms, making the latter two more suitable as sensitizers. Consequently, C2‐COOH may not be the optimal anchoring point for TiO2 in the investigated betanin forms, especially when compared to the more favorable C17‐COOH anchoring point.

Mechanistic Insights into Cs-Ion Exchange in the Zeolite Chabazite from In Situ Powder X-Ray Diffraction.

Zeolites contain extraframework cations that are exchangeable under favorable aqueous conditions; this is the fundamental feature for their application in water purification and necessary to produce cation forms for other applications such as catalysis. Optimization of the process is common, but there is little fundamental understanding based on real-time experiments of the mechanism of exchange for most zeolites. The sodium and potassium forms of zeolite chabazite selectively uptake Cs+ by ion exchange, leading to its application in removing radioactive 137Cs+ from industrial nuclear waste streams, as well as from contaminated environments in the aftermath of the Fukushima and Three Mile Island accidents. In this study, in situ synchrotron powder X-ray diffraction patterns have been collected on chabazite as it undergoes Cs-ion exchange. Applying Rietveld refinement to these patterns has revealed the time-resolved structural changes that occur in the zeolite as exchange progresses, charting the changes in the spatial distribution of the extraframework cations and water molecules in the structure during the reaction. Ultimately, a detailed mechanistic understanding of how this dynamic ion-exchange reaction occurs has been obtained.

Study of the process of tetracycline absorption by soil and its transformation during acid desorption

Introduction. Currently, control over the soil entry of antibiotics used in agriculture is becoming an urgent problem of environmental hygiene. Tetracycline can enter the soil with the excrement of domestic animals and affect biological objects, both microbiological and plant. The chemical form of tetracycline in the soil and the options for its transformation, in particular during sample preparation for analysis, are factors that determine the intensity of this effect and the reliability of analytical control. The lack of information about the transformation of the drug under chemical influence determined the relevance of the research. Materials and methods. The studies were performed using the Stayer chromatographic system with a Shodex IC YS-50 150/4.6 cation column and a Kromasil C18 HPLC column with amperometric and conductometric detection. The objects of research were model soil samples with different tetracycline contents. When conducting research, soddy-podzolic soil from the «Nemchinovka» experimental field (Moscow region) and GSO No. chernozem were used. Results. Solutions obtained after acid-methanol desorption of tetracycline from soil samples were studied using HPLC and IC (Ionochromatographic methods). As a result of desorption, complex forms of substances, including both natural organic substances of the soil and tetracycline components, were established to pass into the aqueous phase. These forms of substances are fixed with a Shodex IC YS-50 cation exchange column and are not fixed by HPLC with a Kromasil C18 column. The possibility of isolating a chromatographic signal corresponding to the tetracycline component using ion chromatography has been demonstrated. Limitations. To create a method for measuring tetracycline in soil, it is necessary to test a larger number of soil species that differ in the content of organic matter to identify in detail the interfering effect of the organic matrix during chromatographic analysis. Conclusion. Research has shown tetracycline chemically to bind to soil matter, forming cationic complexes. After treating the soil with a mixture of concentrated hydrochloric acid and methanol, tetracycline is quantitatively extracted from the soil in combination with natural soil organic matter. These forms of substances are detected by a Shodex IC YS-50 cationic column and are not detected by HPLC with a Kromasil C18 column. Selective analysis of the cationic form containing the tetracycline moiety is possible.

Beta-Irradiation of pure 1-alkyl-3-methylimidazolium-based ionic liquids

1-Alkyl-3-methylimidazolium ionic liquids are common cellulose solvents and biomass pretreatment agents, while beta-irradiation (“e-beaming”) is often used to decrease the recalcitrance of biomass towards hydrolysis or saccharification. Aiming at the general goal of elucidating the interaction between lignocellulosics, imidazolium-based ionic liquids, and beta-irradiation, we studied the effect of beta-irradiation on the pure ILs 1-ethyl-3-methylimidazolium and 1-butyl-3-methylimidazolium, both as chloride and acetate. Contrary to the expectation of inertness, irradiation caused degradation of the ILs, which was proportional to irradiation dosage, i.e., to irradiation time and intensity. At a dosage of 2400 kGy, 0.2% (2000 ppm) of the IL were chemically altered. The main degradation pathway is the formation of imidazole and N-methylimidazole with concomitant dealkylation. The cleaved-off alkyl groups, apparently in cationic form, react with the anions present, accounting for the formation of alkyl chlorides and alkyl acetates from the chloride ILs and acetate ILs, respectively. A second, minor pathway comprises the degradation of the imidazole ring under conversion of the C2-unit from the former C4-C5 moiety into ethylenediamine and reaction of the C1-unit from the former C2 with the IL anions. Because of the non-neglible byproduct formation, the degradation of the ILs upon beta-irradiation and possible side reactions of the resulting byproducts need to be kept in mind for all setups that involve beta-irradiation and imidazolium ILs simultaneously.Graphical abstract

Synthesis, molecular dynamics, antimicrobial activity and wound healing application of new methylidene dyes based on pyrrolinone esters

A new methylidene dye based on the direct condensation of an aldehyde derivative with a pyrrolinone ester derivative was successfully prepared as well as its quaternary ammonium salt analogue. The structures of all synthesized dyes were confirmed using NMR, Mass and IR spectra. The absorption and emission spectra of the synthesized dyes were investigated. The synthesized methylidene dye and its cationic form showed high molar absorption coefficients and a significant emission of the cationic dye analogue solution was observed. The antibacterial affinity using the disk diffusion method was investigated for six potential skin infection causing microbial pathogens, including two Gram-negative species (Pseudomonas aeruginosa and Proteus mirabilis), two Gram-positive species (Staphylococcus aureus and Staphylococcus epidermidis), and two fungal species (Candida albicans and Rhizomucor miehei) by recording the inhibition zone as well as studying the killing time effect for the prepared dyes. The in vitro wound healing application and the effect of cationized Dye 2 on the healing progress showed very effective and faster healing at a concentration of 100 µg/mL (IC50). Molecular dynamics simulation studies of Dye 1 and Dye 2 were carried out to compute binding free energies using Generalized Born Surface Area (MM/GBSA) in molecular mechanics. Furthermore, computational studies revealed that Dye 2 showed high affinity toward the active site of DNA gyrase B, which provides a solid framework for new structure-based design initiatives.

A 2-dimensional modelling of the coating process of nickel on polyurethane foam via electrodeposition

A numerical model is proposed to investigate the electrodeposition coating process of open-porous polyurethane (PU) foams with nickel. The modelling approach is based on the mixture theory, which accounts for the multi-phase nature of the system comprising the porous foam structure and the electrolyte which consists of the deposition material in form of cations. The model takes into consideration various physical and electrochemical phenomena, including different ionic transport mechanisms, i.e. diffusion, convection and migration. By solving the governing equations numerically, the coating process and the relevant variables are predicted over time. The simulation results are compared with experimental data to assess the agreement between the model and the experimental results. The findings reveal that the numerical model provides valuable insights into the electrodeposition process and facilitates a deeper understanding of the underlying mechanisms and it can be used for optimizing the coating process parameters.

Comparison of hexavalent chromium and cadmium removal from wastewater in constructed rapid infiltration system with layered double hydroxides (LDHs) modified maifanite substrates: Physical, chemical and microbial mechanism

In order to protect the ecological environment on which human beings depend, it is of great practical significance to prevent and control the heavy metal pollution in surface water. Cr(VI) in anionic form and Cd(II) in cationic form were selected to conduct the heavy metal purification experiments. Cr(VI) and Cd(II) removal by constructed rapid infiltration systems (CRIS) contain Zn-CO3-LDHs (ZnAl-CO3-LDHs and ZnFe-CO3-LDHs) coated maifanite substrates were compared. After ZnAl-CO3-LDHs coated, the Cr(VI) and Cd(II) removal amount increased by 87.53 % and 19.00 %, respectively. It could be inferred from XRD, FTIR, and Zeta potential results that the Cr(VI) physicochemical removal mechanism of maifanite changed to anion exchange, chemical bonding and electrostatic adsorption from electrostatic adsorption and chemical bonding after Zn-CO3-LDHs coated. By contrast, isomorphous replacement, electrostatic adsorption and chemical bonding of Cd(II) induced by Zn-CO3-LDHs replaced the electrostatic adsorption by natural maifanite. Additionally, the effective Cr(VI)/Cd(II) accumulation on Zn-CO3-LDHs modified maifanite reduced the microbial quantity, but increased EPS secretion and changed the community structure, which achieved the microbial Cr(VI)/Cd(II) removal through extracellular complexation and intracellular accumulation. This research result may provide essential reference for exploring the feasibility of heavy metal removal of CRIS with LDHs modified substrate.

Interaction of melanoidins, proline, and valine with sorbents of various nature

The isolation of pure amino acids from industrial solutions is one of the important tasks of production. Solutions of amino acids obtained as a result of chemical or microbiological treatment contain a number of impurities, mostly organic ones. The microbiological synthesis of proline is accompanied by the presence of valine, leucine, alanine, and coloured high-molecular components in the culture liquid that belong to the melanoidin group. Melanoidins of proline acid production are high-molecular compounds containing amino acid fragments, heterocyclic structures, and amide bonds. Melanoidins in solutions can exist in cationic, bipolar, and anionic forms. They have different molecular weights, molecular sizes, and isoelectric states. Various ion exchange methods can be used to isolate the target amino acid. It should be noted that the interaction of amino acids with ion-exchange materials is a complex process depending on the electrolytic properties of the sorbate and sorbent and accompanied by multiple side effects. It is necessary to know the specific features of interaction in the “amino acid - sorbent” system and the factors that affect the transport of sorbate ions in the sorbent phase when choosing an isolation method for the target product. The goal of this work was to determine the impact of pH on the sorption process of proline and valine by high-basic ion exchangers, to identify the features of their interactions, and to use the obtained results to optimise the conditions for the separation of amino acids. We studied the process of interaction of bipolar ions and anions of proline (Pro±, Pro-) and valine (Val±, Val-) with anionites AV-17-8 and AV-17-2P. It was established that the mechanism of amino acid ion exchange in granular sorbents depended on the рН value in the “anionite - external solution” system. Based on the studied interactions, we suggested the methods of the anion-exchange separation of proline and valine. The selected conditions of separation of proline and valine were on anionite AV-17-2P in ОН-form (рН of the initial solution was 6.6-6.7; the solution flow rate was 2 cm3/min). The results of separation of proline and valine indicated that even in a one-step sorption process, five to seven fractions with proline contained no valine ions, while the concentration of proline was 2.0-2.7 times higher as compared to the original solution.

Samarium(III) Removal by Weak Acid Exchanger Amberlite IRC-50 in (H+) and (Na+) Forms

Adsorption of samarium(III) on a weakly macroporous cation exchanger Amberlite IRC-50 (H+) and (Na+) forms is studied as a function of the initial pH of the aqueous solution, time and temperature, initial samarium(III) ion concentration, and the amount of resin at a fixed temperature (20 ± 1 °C). The concentration range was between 0.1–5 mmol/L, the pH range was between 1.8 and 10.5; the stirring time was between 2 and 60 min; and the amount of resin was between 0.025 and 0.15 g. Both the film and particle diffusion equations are applied to explain the kinetic data. The rate constant values for samarium(III) adsorption were calculated for both film and particle diffusion processes. It is observed to follow the order (Na+) > (H+). Temperature is found to have an insignificant effect on both diffusional processes. Various thermodynamic parameters (ΔH°, ΔS°, and ΔG°) from samarium(III) exchange on the resin were calculated. The optimum conditions were found to be a concentration of 1 mmol/L, pH of 9.3, stirring time of 20 and 5 min for Amberlite IRC-50 (H+) and (Na+) forms, respectively, and 0.15 g of resin. The equilibrium extraction of samarium was 22.2 mg/g for Amberlite IRC-50 (H+) and 21.9 mg/g for Amberlite IRC-50 (Na+) at an initial concentration of 1 mmol/L. The results obtained show that the Amberlite IRC-50 weak cationexchange resin performed well for the removal and recovery of samarium(III). The optimization procedure provides access to industrial-scale Sm(III) removal processing.

Highly sulfonated hyper-cross-linked polymers as promising adsorbents for efficient and selective removal of ciprofloxacin from water

This study aims at the development of novel and highly sulfonated hyper-cross-linked polymers (sHCPs) using facile and one-step synthetic approach, and verification of the potential applicability of the as-synthesized polymers in the adsorptive removal of various antibiotic pollutants under environmentally relevant conditions. The sHCPs synthesized in this work were capable of highly efficient removal of antibiotic pollutants at relatively high (30 mg/L) and low (50 µg/L) initial concentrations, both from a simple as well as complex water matrices. The rate of ciprofloxacin removal and the adsorption capacity observed for the most efficient adsorbent (qe = 757.7 mg/g) were found to be approximately twice higher than that established for other previously reported sulfonated polymers prepared via post-synthetic sulfonation (qe = 476.9 mg/g), and commercial polymer-based adsorbents (e.g. Amberlyst-15, qe = 438.5 mg/g). The highest adsorption capacity was observed at pH close to neutral for polar antibiotic pollutants that contain protonated functional groups and exist in cationic or zwitterion form (e.g. ciprofloxacin and tetracycline). The reported results clearly imply that highly sulfonated hyper-cross-linked polymers are promising candidates for potential practical application for the elimination of organic pollutants from aqueous media, being capable of selective removal of various antibiotics via ionic interaction even in the presence of a great excess of other cations, anions and organic matter naturally existing in environmentally relevant water samples (e.g. river water).

Redox-gated recognition of dihydrogen phosphate using a ferrocene-tethered non-symmetric aryl-triazole pentad

ABSTRACT Anions play many roles in our environment. Consequently, the development of synthetic receptors capable of targeted anion binding is of ongoing importance. While many such receptors are known, simplified designs and measurement approaches are always beneficial. Herein, we report the synthesis of a non-symmetric aryl-triazole pentad receptor appended with a single ferrocene, its electrochemistry, and the selective binding to dihydrogen phosphate (H2PO4 –) anions of its oxidised form over various environmentally prevalent anions (HSO4 –, Cl–, NO3 –). The receptor was constructed using a modular architecture with simple installation of a ferrocene unit using click chemistry. Electrochemical analysis on the receptor revealed that addition of H2PO4 – anion led to a shift in the redox peaks of the receptor (FcP) towards more negative potentials, indicating higher anion affinity was achieved after the ferrocene was oxidised to its cationic form (FcP + ). This work verifies prior studies on the efficacy of cationic charge in simpler receptor design for the creation of functional host-guest systems.

Effect of counterions on the water sorption and glass transition properties of maltobionate salts

AbstractThe purpose of this study was to clarify the effect of counterions on the water sorption and glass transition properties of maltobionate salts. Sodium maltobionate (NaMb), potassium maltobionate (KMb), and magnesium maltobionate (MgMb2) were employed, and the values for calcium maltobionate (CaMb2) and maltose were taken from the literature. The water sorption isotherm of the samples was characterized using the Guggenheim-Anderson-de Boer model. The glass transition temperature (Tg) and freeze-concentrated glass transition temperature (Tg’) were evaluated by differential scanning calorimetry. The effect of water content on the Tg was analyzed using the Gordon-Taylor model. The order of the anhydrous Tg values of maltobionate salts was: KMb < NaMb < maltose < MgMb2 < CaMb2. The anhydrous Tg of the divalent cation forms (MgMb2 and CaMb2) was much higher than that of the monovalent cation forms (NaMb and KMb). The anhydrous Tg will be affected by the plasticizing effect and electrostatic effect of cations. The Tg depression induced by water plasticizing was greater for KMb than for the other maltobionate salts. The order of Tg’ values of freeze-concentrated maltobionate salts was: KMb < maltose < NaMb < MgMb2 < CaMb2. This trend was almost the same as that seen for anhydrous Tg, but the range of the Tg’ values (242.2–257.8 K) was much lower than that of the anhydrous Tg (346.9–421.3 K). The Tg’ appears to be affected by the strength of ionic interactions and amount of unfrozen water.

Probing solution conformations of l-DOPA: Integration of experiment and simulation via vibrational optical activity

l-DOPA plays a critical role as a precursor to dopamine and is a standard treatment for Parkinson's disease. Recent research has highlighted the potential therapeutic advantages of deuterated l-DOPA analogs having a longer biological half-life. For their spectroscopic characterization, the in-detail characterization of l-DOPA itself is necessary. This article presents a thorough examination of the vibrational spectra of l-DOPA, with a particular emphasis on chirally sensitive VOA techniques. We successfully obtained high-quality Raman and ROA spectra of l-DOPA in its cationic form, under low pH conditions, and at a high concentration of 100 mg/ml. These spectra cover a broad spectral range, allowing for precise comparisons with theoretical simulations. We also obtained IR and VCD spectra, but they faced limitations due to the narrow accessible spectral region. Exploration of l-DOPA's conformational landscape revealed its intrinsic flexibility, with multiple coexisting conformations. To characterize these conformations, we employed two methods: one involved potential energy surface scans with implicit solvation, and the other utilized molecular dynamics simulations with explicit solvation. Comparing ROA spectra from different conformer groups and applying spectral decomposition proved crucial in determining the correct conformer ratios. The use of explicit solvation significantly improved the quality of the final simulated spectral profiles. The accurate determination of conformer ratios, rather than solely relying on the number of averaged spectra, played a crucial role in simulation accuracy. In conclusion, our study offers valuable insights into the structure and conformational behavior of l-DOPA and represents a valuable resource for subsequent spectroscopic studies of its deuterated analogs.

Adsorption isotherm and kinetic study of Bengkulu Kaolinite in removing ferrous cation by continuous operation

Iron is a chemical element that is found in groundwater that can be suspended in the form of ferrous cations. Iron presence that exceeds the threshold can cause detrimental effects such as piping corrosion, bad smells, and health problems. According to observations, groundwater in Sukarame, Bandar Lampung, has smells and colors that indicate iron metal contamination. Hence, it is necessary to research reducing the iron content. The method used in this research is the adsorption method using kaolin adsorbent that has been activated by physical activation at 700°C. The adsorption was conducted continuously with various reactor heights of 20 cm, 15 cm, and 10 cm. The results showed that the most significant reduction in efficiency was found in the adsorption using reactors with a height of 20 cm by 92%. The adsorption phenomenon using a reactor height of 20 cm followed the Langmuir isotherm model (R2 = 0.9255) with an adsorption capacity of 17.03 mg/g. The kinetic data correlated well with the pseudo-second-order equation (R2 = 0.9313). It can be concluded that kaolin adsorbent can reduce iron levels, in which the adsorption using reactors with a height of 20 cm is the most effective.

Exploring the bonding and aromaticity of [Au3{C2H2N2E(L)2}3]+ (E = Si, Ge and L = –CH3, -H, -CF3, –NO2): Trinuclear gold superalkali complexes

Coinage metal [Cu, Ag, Au] complexes, with carbene analogous ligands, especially silylene, and germylene, have been getting attention in recent years for their potential applications, either in homogeneous catalysis or in photophysical properties. In this study, we have designed trinuclear gold complexes with different substituted silylene and germylene and observed that these trinuclear gold complexes are stable in cationic form and behave like a superalkali. Conceptual density functional theory (CDFT) based descriptors like electrophilicity give the idea about the reactivity of these superalkali complexes. Negative NICS values determine the aromatic nature of the trinuclear core of these complexes. Atom in molecules (AIM) study has been performed to gain a clear idea about the bonding nature of complexes. Energy decomposition analysis (EDA) suggests that electrostatic interaction stabilizes the complex. First-order hyperpolarizability calculation confirms their high nonlinear optical (NLO) properties.

A modern polymer based wound care coating for wound management

Pain management at phase 1 of the wound process includes wound cleaning due to the lysis of purulent-necrotic masses, control of the pathogenic microflora, and evacuation of wound discharge. These factors are achievable with a new composite depo-material having the textile base, hydrogel composition based on biopolysaccharide sodium alginate with immobilized active components – proteolytic enzyme of plant origin- papain and antimicrobial salt-like silver. Biosynthesis of silver nanoparticles and its presence in the composition in the cation form increases efficacy and eliminates toxicity of the treatment due to low silver concentration.

Towards Amplified Probing of Weak Intermolecular Interactions on the External Surfaces of Molecular Capsules.

We report a sensitive method for comparing weak interactions between aryl rings located on the external surfaces of equilibrating homo- and heterodimeric capsules. Two identical self-complementary resorcin[4]arene tetrabenzoate molecules and one tetramethylammonium cation form in CDCl3 hydrogen-bonded homodimeric capsules whose exteriors are decorated with four tight pairs of weakly interacting aryl rings. The pair wise mixing of six different homodimers establishes their equilibria with the corresponding heterodimeric species in which two types of aryl rings exert on each other some gentle forces. This equilibrium is significantly shifted either towards homo- or heterodimers depending on the nature and location of the substituents in the weakly interacting aryl rings. The thermodynamic favorability or disadvantage of the heterodimerization is determined by stronger or weaker aryl-aryl attractions in the hetero- or homodimeric capsules, respectively. The four-fold amplification of weak aryl-aryl interactions on the external surfaces of the equilibrating capsules is responsible for high sensitiveness of our approach.

Electrochemical, spectroelectrochemical, and electrochromic characterization of silicon(IV) phthalocyanine with axially ligated electropolymerizable 3,4-ethylenedioxythiophene moieties

Poly(3,4‐ethylenedioxythiophene) (PEDOT) is the most popular conducting polymer in the field of optoelectronics. In this study, the electrochemical and spectral properties of the silicon(IV) phthalocyanine (SiPc) and of a PEDOT were combined, and the electrochromic property was imparted to SiPc by modification of the axial positions of the Si4+ cation of SiPc with 3,4‐ethylenedioxythiophene (EDOT) groups. For this purpose, SiPc-EDOT was synthesized and characterized as to its electrochemistry and spectroelectrochemistry in nonaqueous media. Three reversible reduction couples at −0.51, −0.92, and −1.62 V and two oxidation processes at 1.16 and 1.73 V were observed for SiPc-EDOT in dichloromethane (DCM) containing tetrabutylammonium perchlorate (TBAP). In situ spectroelectrochemical analysis showed that the reductions and the first oxidation process of SiPc-EDOT were Pc-centered and the second oxidation process was EDOT-centered. The EDOT-based redox process at 1.73 V triggered the coating of SiPc-EDOT on the electrode surface as the SiPc-PEDOT film due to the electrooligomerization of the oxidative cationic form of EDOT groups during the repetitive voltammetric cycles. The electropolymerized SiPc-PEDOT film on the different electrode surfaces (ITO, GCE, ITO/Nf) yielded a conjugated polymer, which was characterized by cyclic voltammetry, UV–vis spectroelectrochemistry, Raman and FT-IR spectroscopies. The EDOT modification of SiPc supplied boost electrochromic performance in large percent transmittance change (Δ%T = 50 %), high coloration efficiency (η = 530 cm2 C−1), fast response times, and high cycle stability.

Degradation of enoxacin with different dissociated species during the transformation of ferrihydrite-antibiotic coprecipitates

Ferrihydrite acts as a natural reservoir for nutrient elements, organic matter, and coexisting pollutants through adsorption and coprecipitation. However, the degradation of emerging fluoroquinolone antibiotics during the transformation of ferrihydrite coprecipitates, especially those with various dissociated species, remains insufficiently explored. In this study, Enoxacin (ENO), employed as a model antibiotic, was introduced to prepare ferrihydrite-ENO coprecipitates. The influence of coprecipitated ENO on the transformation of the ferrihydrite-ENO coprecipitate was investigated across different pH conditions. The results revealed that ferrihydrite-ENO coprecipitates thermodynamically transformed into more stable goethite and/or hematite under all pH conditions. In neutral and alkaline conditions, ENO promoted the transformation of coprecipitates into goethite while hindering hematite formation. Conversely, under acidic conditions, ENO directly obstructed the transformation of coprecipitates into hematite. Different dissociated species of ENO displayed distinct degradation pathways. The cationic form of ENO exhibited a greater tendency for hydroxylation and defluorination, while the zwitterion form leaned toward piperazine ring oxidation, with limited preference for quinolone ring oxidation. The anionic form of ENO exhibited the fastest degradation rate. It is essential to emphasize that the toxicity of the degradation products was intricately connected to the specific reaction sites and the functional groups they acquired post-oxidation. These findings offer fresh insights into the role of antibiotics in coprecipitation, the transformation of ferrihydrite coprecipitates, and the fate of coexisting antibiotics.

Copper Single Atoms Chelated on Ligand-Modified Carbon for Ullmann-type C-O Coupling.

Cross-coupling reactions are of great importance in chemistry due to their ability to facilitate the construction of complex organic molecules. Among these reactions, the Ullmann-type C-O coupling between phenols and aryl halides is particularly noteworthy and useful for preparing diarylethers. However, this reaction typically relies on homogeneous catalysts that rapidly deactivate under harsh reaction conditions. In this study, we introduce a novel heterogeneous catalyst for the Ullmann-type C-O coupling reaction, comprised of isolated Cu atoms chelated to a tetraethylenepentamine-pyrrole ligand that is immobilized on graphite nanoplatelets. The catalytic study reveals the recyclability of the material, and demonstrates the crucial role of the pyrrole linker in stabilizing the Cu sites. The work expands the potential of single-atom catalyst nanoarchitectures and underscores the significance of ligands in stabilizing metals in cationic forms, providing a novel, tailored catalyst for cross-coupling chemistries.