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Accounts of Chemical Research Nov 2023Aerobic organisms involve dioxygen-activating iron enzymes to perform various metabolically relevant chemical transformations. Among these enzymes, mononuclear non-heme...
Aerobic organisms involve dioxygen-activating iron enzymes to perform various metabolically relevant chemical transformations. Among these enzymes, mononuclear non-heme iron enzymes reductively activate dioxygen to catalyze diverse biological oxidations, including oxygenation of C-H and C═C bonds and C-C bond cleavage with amazing selectivity. Several non-heme enzymes utilize organic cofactors as electron sources for dioxygen reduction, leading to the generation of iron-oxygen intermediates that act as active oxidants in the catalytic cycle. These unique enzymatic reactions influence the design of small molecule synthetic compounds to emulate enzyme functions and to develop bioinspired catalysts for performing selective oxidation of organic substrates with dioxygen. Selective electron transfer during dioxygen reduction on iron centers of synthetic models by a sacrificial reductant requires appropriate design strategies. Taking lessons from the role of enzyme-cofactor complexes in the selective electron transfer process, our group utilized ternary iron(II)-α-hydroxy acid complexes supported by polydentate ligands for dioxygen reduction and bioinspired oxidations. This Account focuses on the role of coordinated sacrificial reductants in the selective electron transfer for dioxygen reduction by iron complexes and highlights the versatility of iron(II)-α-hydroxy acid complexes in affecting dioxygen-dependent oxidation/oxygenation reactions. The iron(II)-coordinated α-hydroxy acid anions undergo two-electron oxidative decarboxylation concomitant with the generation of reactive iron-oxygen oxidants. A nucleophilic iron(II)-hydroperoxo species was intercepted in the decarboxylation pathway. In the presence of a Lewis acid, the O-O bond of the nucleophilic oxidant is heterolytically cleaved to generate an electrophilic iron(IV)-oxo-hydroxo oxidant. Most importantly, the oxidants generated with or without Lewis acid can carry out -dihydroxylation of alkenes. Furthermore, the electrophilic iron-oxygen oxidant selectively hydroxylates strong C-H bonds. Another electrophilic iron(IV)-oxo oxidant, generated from the iron(II)-α-hydroxy acid complexes in the presence of a protic acid, carries out C-H bond halogenation by using a halide anion.Thus, different metal-oxygen intermediates could be generated from dioxygen using a single reductant, and the reactivity of the ternary complexes can be tuned using external additives (Lewis/protic acid). The catalytic potential of the iron(II)-α-hydroxy complexes in performing O-dependent oxygenations has been demonstrated. Different factors that govern the reactivity of iron-oxygen oxidants from ternary iron(II) complexes are presented. The versatile reactivity of the oxidants provides useful insights into developing catalytic methods for the selective incorporation of oxidized functionalities under environmentally benign conditions using aerial oxygen as the terminal oxidant.
Topics: Lewis Acids; Oxygen; Reducing Agents; Iron; Oxidation-Reduction; Oxidants; Ferrous Compounds; Hydroxy Acids
PubMed: 37938969
DOI: 10.1021/acs.accounts.3c00449 -
Environmental Science & Technology Jun 2023Fe(IV) and Fe(V) are promising oxidants for the selective removal of emerging organic contaminants (EOCs) from water under near-neutral conditions. The Fe(III)-assisted...
Fe(IV) and Fe(V) are promising oxidants for the selective removal of emerging organic contaminants (EOCs) from water under near-neutral conditions. The Fe(III)-assisted electrochemical oxidation system with a BDD anode (Fe(III)-EOS-BDD system) has been employed to generate Fe(VI), while the generation and contributions of Fe(IV) and Fe(V) have been largely ignored. Thus, we examined the feasibility and involved mechanisms of the selective degradation of EOCs in the Fe(III)-EOS-BDD system under near-neutral conditions. It was found that Fe(III) application selectively accelerated the electro-oxidation of phenolic and sulfonamide organics and made the oxidation system be resistant to interference from Cl, HCO, and humic acid. Several lines of evidence indicated that EOCs were decomposed via direct electron-transfer process on the BDD anode and by Fe(IV) and Fe(V) but not Fe(VI), besides HO. Fe(VI) was not generated until the exhaustion of EOCs. Furthermore, the overall contributions of Fe(IV) and Fe(V) to the oxidation of phenolic and sulfonamide organics were over 45%. Our results also revealed that Fe(III) was oxidized primarily by HO to Fe(IV) and Fe(V) in the Fe(III)-EOS-BDD system. This study advances the understanding of the roles of Fe(IV) and Fe(V) in the Fe(III)-EOS-BDD system and provides an alternative for utilizing Fe(IV) and Fe(V) under near-neutral conditions.
Topics: Diamond; Boron; Ferric Compounds; Water; Oxidants; Oxidation-Reduction; Water Pollutants, Chemical; Electrodes
PubMed: 37294905
DOI: 10.1021/acs.est.3c01850 -
Chemosphere Nov 2021Pharmaceuticals may pose serious potential risks, such as biological responses and chronic health effects, due to their ubiquitous in natural aquatic water bodies. In...
Pharmaceuticals may pose serious potential risks, such as biological responses and chronic health effects, due to their ubiquitous in natural aquatic water bodies. In this study, we proposed an effective, feasible, and low-cost strategy for the abatement of pharmaceuticals (i.e., phenylbutazone (PBZ) and sulfinpyrazone (SPZ)) via CoO nanoparticles (NPs) as heterogeneous catalyst in permanganate (Mn(VII)) oxidation for the first time. The performance of the CoO NPs in permanganate oxidation is highly dependent on pH and its dosage. CoO NPs play as electron shuttles in the catalytic permanganate oxidation process involving one-electron transfer with the oxidation of ≡Co to ≡Co by permanganate and the formation of colloidal manganese dioxide (MnO), as well as the reduction of the newly formed ≡Co to ≡Co by organics and the production of oxidized organic byproducts. The degradation pathways of PBZ and SPZ in catalytic permanganate oxidation were proposed based on the liquid chromatography-tandem mass spectrometry (LC-MS/MS) results and Gaussian calculation, and the toxicity decay of pharmaceuticals during oxidation was observed. Considering the stability, reusability, and cost, CoO coupled with Mn(VII) is suitable for water pretreatment and is potentially feasible for industrial application, which is not only effective for decomposing PBZ and SPZ, but also for eliminating their toxicity.
Topics: Chromatography, Liquid; Manganese Compounds; Nanoparticles; Oxidation-Reduction; Oxides; Pharmaceutical Preparations; Tandem Mass Spectrometry
PubMed: 34119724
DOI: 10.1016/j.chemosphere.2021.131115 -
Chemosphere May 2024Azo dyes are largely used in many industries and discharged in large volumes of their effluents into the aquatic environment giving rise to non-esthetic pollution and... (Review)
Review
Azo dyes are largely used in many industries and discharged in large volumes of their effluents into the aquatic environment giving rise to non-esthetic pollution and health-risk problems. Due to the high stability of azo dyes in ambient conditions, they cannot be abated in conventional wastewater treatment plants. Over the last fifteen years, the decontamination of dyeing effluents by persulfate (PS)-based advanced oxidation processes (AOPs) has received a great attention. In these methods, PS is activated to be decomposed into sulfate radical anion (SO), which is further partially hydrolyzed to hydroxyl radical (OH). Superoxide ion (O) and singlet oxygen (O) can also be produced as oxidants. This review summarizes the results reported for the discoloration and mineralization of synthetic and real waters contaminated with azo dyes covering up to November 2023. PS activation with iron, non-iron transition metals, and carbonaceous materials catalysts, heat, UVC light, photocatalysis, photodegradation with iron, electrochemical and related processes, microwaves, ozonation, ultrasounds, and other processes is detailed and analyzed. The principles and characteristics of each method are explained with special attention to the operating variables, the different oxidizing species generated yielding radical and non-radical mechanisms, the addition of inorganic anions and natural organic matter, the aqueous matrix, and the by-products identified. Finally, the overall loss of toxicity or partial detoxification of treated azo dye solutions during the PS-based AOPs is discussed.
Topics: Azo Compounds; Water Pollutants, Chemical; Iron; Oxidation-Reduction; Oxidants; Water
PubMed: 38527631
DOI: 10.1016/j.chemosphere.2024.141766 -
Colloids and Surfaces. B, Biointerfaces Jan 2022Sonodynamic therapy, which utilizes ultrasound (US) to produce cytotoxic reactive oxygen species (ROS), can overcome the critical drawbacks of photodynamic therapy, such...
Sonodynamic therapy, which utilizes ultrasound (US) to produce cytotoxic reactive oxygen species (ROS), can overcome the critical drawbacks of photodynamic therapy, such as limited tissue penetration depth. However, the development of sonosensitizers having superior sonodynamic effects and desirable biocompatibility remains a major challenge. In this study, nanoscale zirconium-based porphyrinic metal organic frameworks (MOFs) (PCN-222) were developed as safe and effective nanosonosensitizers. Polyethylene glycol (PEG)-coated PCN-222 (PEG-PCN) was loaded with a pro-oxidant drug, piperlongumine (PL), to enable tumor-specific chemo-photodynamic combination therapy. Both PEG-PCN and PL-incorporated PEG-PCN (PL-PEG-PCN) showed high colloidal stability in biological media. In addition, nanoscale PL-PEG-PCN was efficiently internalized by breast cancer cells, leading to substantially increased ROS generation under US exposure. The effective intracellular delivery of PL by PEG-PCN further elevated the level of intracellular ROS in breast cancer cells owing to the pro-oxidative activity of PL. Therefore, PL-PEG-PCN revealed significantly higher sonotoxicity than free PL and PEG-PCN. Owing to the cancer-specific apoptosis triggered by PL, PL-PEG-PCN showed cancer-selective cell death in breast cancer cells compared with normal fibroblast cells. This study demonstrates that pro-oxidant drug-loaded porphyrinic MOFs are biocompatible and effective sonosensitizers for cancer-targeted chemo-sonodynamic combination therapy.
Topics: Metal-Organic Frameworks; Neoplasms; Oxidants; Prodrugs; Reactive Oxygen Species; Zirconium
PubMed: 34752984
DOI: 10.1016/j.colsurfb.2021.112189 -
Environmental Science & Technology Mar 2020Dissolved organic matter (DOM) is ubiquitous in raw drinking water and can efficiently scavenge oxidants, such as permanganate. Here, changes to DOM induced by...
Dissolved organic matter (DOM) is ubiquitous in raw drinking water and can efficiently scavenge oxidants, such as permanganate. Here, changes to DOM induced by permanganate oxidation under typical drinking water treatment conditions (6 μM, 1 h) to bulk DOM properties, DOM functional groups, and DOM chemical formulae were examined for two DOM isolate types (terrestrial and microbial). Permanganate oxidation did not mineralize DOM, rather changes were compositional in nature. Optical properties suggest that permanganate oxidation decreased DOM aromaticity (decreased SUVA-254), decreased DOM electron-donating capacity, and decreased DOM average molecular weight (increased E2/E3 ratios). Fourier-transform-infrared spectroscopy second derivative analyses revealed that permanganate does not oxidize DOM alkene groups, suggesting permanganate access to functional groups may be important. Four ionization techniques were used with ultrahigh-resolution mass spectrometry: negative and positive ion mode electrospray ionization and negative and positive ion mode laser/desorption ionization. The results from all four techniques were combined to understand changes in DOM chemical formulae. It was concluded that nitrogen-containing aromatic compounds and alkylbenzenes were oxidized by permanganate to form nitrogen-containing aliphatic compounds and benzoic acid-containing compounds. This work highlights how multiple ionization techniques coupled with UHR-MS can enable a more detailed characterization of DOM.
Topics: Drinking Water; Manganese Compounds; Oxidation-Reduction; Oxides; Water Purification
PubMed: 32083469
DOI: 10.1021/acs.est.9b06675 -
Environmental Research Aug 2022The oxidation of polycyclic aromatic hydrocarbons (PAHs) determines their lifetime, toxicity and consequent environmental and climate impacts. The residential solid fuel...
The oxidation of polycyclic aromatic hydrocarbons (PAHs) determines their lifetime, toxicity and consequent environmental and climate impacts. The residential solid fuel burning composes of a substantial fraction of PAH emissions; however, their oxidation rate is yet to be explicitly understood, which is complicated by the contrasting emission factors under different combustion conditions and their subsequent evolution in the atmosphere. Here we used a plume evolution chamber using ambient oxidants to simulate the evolution of residential solid fuel burning emissions under real-world solar radiation, and then to investigate the oxidation process of the emitted PAHs. Contrasting oxidation rate of PAHs was found to be influenced by particles with or without presence of substantial amount of black carbon (BC). In the flaming burning phase, which contained 46% of BC mass fraction and 8% of organic aerosol (OA) internally mixed with BC, the larger PAHs (with 4-7 rings) was rapidly oxidized 12% for every hour of evolution under solar radiation; however, the larger PAHs from smoldering phase tended to maintain unmodified during the evolution, when 95% of OA was externally mixed with only minor fraction of BC (<5%). This may be ascribed to the complex morphology of BC, allowing more exposure for the internally-mixed OA to the oxidants; in contrast with those externally-mixed OA which was prone to be coated by condensed secondary substances. This raises an important consideration about the particle mixing state in influencing the oxidation of PAHs, particularly the coating on PAHs which may extend their lifetime and environmental impacts.
Topics: Aerosols; Air Pollutants; Biomass; Environmental Monitoring; Oxidants; Polycyclic Aromatic Hydrocarbons; Soot
PubMed: 35305979
DOI: 10.1016/j.envres.2022.113107 -
Molecules (Basel, Switzerland) Oct 2022The Mitsunobu reaction plays a vital part in organic chemistry due to its wide synthetic applications. It is considered as a significant reaction for the interconversion... (Review)
Review
The Mitsunobu reaction plays a vital part in organic chemistry due to its wide synthetic applications. It is considered as a significant reaction for the interconversion of one functional group (alcohol) to another (ester) in the presence of oxidizing agents (azodicarboxylates) and reducing agents (phosphines). It is a renowned stereoselective reaction which inverts the stereochemical configuration of end products. One of the most important applications of the Mitsunobu reaction is its role in the synthesis of natural products. This review article will focus on the contribution of the Mitsunobu reaction towards the total synthesis of natural products, highlighting their biological potential during recent years.
Topics: Biological Products; Phosphines; Reducing Agents; Esters; Oxidants
PubMed: 36296545
DOI: 10.3390/molecules27206953 -
The Journal of Hospital Infection Sep 2019Biofilms that develop on dry surfaces in the healthcare environment have increased tolerance to disinfectants. This study compared the activity of formulated oxidizing...
BACKGROUND
Biofilms that develop on dry surfaces in the healthcare environment have increased tolerance to disinfectants. This study compared the activity of formulated oxidizing disinfectants with products containing active ingredients against Staphylococcus aureus dry-surface biofilm (DSB) alone.
METHODS
DSB was grown in the CDC bioreactor with alternating cycles of hydration and dehydration. Disinfectant efficacy was tested before and after treatment with neutral detergent for 30 s, and in the presence or absence of standardized soil. Biofilms were treated for 5 min with peracetic acid (Surfex and Proxitane), hydrogen peroxide (Oxivir and 6% HO solution) and chlorine (Chlorclean and sodium dichloroisocyanurate tablets). Residual biofilm viability and mass were determined by plate culture and protein assay, respectively.
FINDINGS
Biofilm viability was reduced by 2.8 log for the chlorine-based products and by 2 log for Proxitane, but these products failed to kill any biofilm in the presence of soil. In contrast, Surfex completely inactivated biofilm (6.3 log reduction in titre) in the presence of soil. HO products had little effect against DSB. Biofilm mass removed in the presence and absence of soil was <30% by chlorine and approximately 65% by Surfex. Detergent treatment prior to disinfection had no effect.
CONCLUSION
The additives in fully formulated disinfectants can act synergistically with active ingredients, and thus increase biofilm killing whilst decreasing the adverse effect of soil. It is suggested that purchasing officers should seek efficacy testing results, and consider whether efficacy testing has been conducted in the presence of biological soil and/or biofilm.
Topics: Biofilms; Chlorine; Disinfectants; Drug Synergism; Environmental Microbiology; Hydrogen Peroxide; Microbial Viability; Organic Chemicals; Oxidants; Peracetic Acid; Soil; Staphylococcus aureus
PubMed: 30391488
DOI: 10.1016/j.jhin.2018.10.019 -
Environmental Science and Pollution... May 2019Advanced oxidation processes, including UV/HO, are methods able to remove diverse classes of organic contaminants and disinfect water and wastewater. However, the...
Advanced oxidation processes, including UV/HO, are methods able to remove diverse classes of organic contaminants and disinfect water and wastewater. However, the variation in the matrix composition can influence the inactivation of microorganisms due to the presence of competing reactive material, which consumes the available oxidants. This problem can lead to the use of inadequate oxidant/radiation dose and disturb a correct treatment. The aim of this study was to assess the efficiency of UV/HO to inactivate microbiological indicators in secondary effluents in the presence of high concentration of carbonate, nitrate, metals, and industrial organic contaminants. Metals had a positive influence on inactivation acting as catalysts. Zn, Fe, and all metals simultaneously presented toxic effects to the indicator organisms in the higher concentrations before the treatment. Even in metals presence, the negative effect of carbonate and the industrial organic contaminants on indicators inactivation was very important. Bacteria regrowth after 72 h was also affected by the same inhibiting substances, but the metals acted positively inhibiting it. The disinfection indicators had different sensibilities to the spiked substances. Escherichia coli inactivation was more affected than total coliforms by the presence of the industrial contamination, which can lead to different interpretation of inhibition degree depending of the used disinfection indicator.
Topics: Bacteria; Catalysis; Disinfectants; Disinfection; Escherichia coli; Hydrogen Peroxide; Industry; Metals; Oxidants; Oxidation-Reduction; Ultraviolet Rays; Wastewater
PubMed: 30895554
DOI: 10.1007/s11356-019-04705-1