Ortho Hydroxyl Research Articles

C–H bond activation over chitosan based Fe(III) and Ni(II) catalysts

Chitosan (Cs) supported heterogeneous catalysts of Fe(III) and Ni(II) is developed by the equimolar reaction of two schiff base ligands, L1 [Cs-HACP] and L2 [ANI-HACP] and Metal salts {where Metal = Fe(III) and Ni(II)}with chitosan. The L1 ligand is prepared by the reaction of chitosan (Cs) and ortho hydroxyl (HACP) acetophenone in methanol and L2 ligand is prepared by the condensation of aniline (ANI) and ortho hydroxyl acetophenone (HACP) in solvent free condition. The prepared catalysts {M-[Cs-L1-L2]Cl2} are characterized by different analytical techniques viz. scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), powder X-ray diffraction (XRD), Thermogravimetric analysis (TGA), Fourier transform infrared (FTIR), Raman, UV-VIS-NIR, X-ray photoelectron spectroscopy (XPS) and computational studies. The catalytic behavior of newly synthesized catalysts are tested for the C–H activation using 70 % tert-butyl hydroperoxide (TBHP). The best results are obtained for tetralin oxidation. The order of catalytic reactivity of {M-[Cs-L1-L2]Cl2}catalyst is in decreasing order: {Fe(III)-[Cs-L1-L2]Cl2} > {Ni(II)-[Cs-L1-L2]Cl2}. The {Fe(III)-[Cs-L1-L2]Cl2} gives maximum conversion 81.99 % of tetralin with 84.50 % selectivity of tetralone (T-lone) and 6.47 % selectivity of tetralol (T-lol) after 5 h of reaction at 80 °C temperature. The chitosan based heterogeneous catalyst is easy to separate and recover. It can be recycled seven times.

Computational assessment of the radical scavenging activity of cleomiscosin.

Coumarinolignans such as cleomiscosin A (CMA), cleomiscosin B (CMB), and cleomiscosin C (CMC) are secondary metabolites that were isolated from diverse plant species. Cleomiscosins (CMs) have numerous interesting biological activities, including noteworthy cytotoxicity of cancer cell lines along with hepatoprotective and assumed antioxidant activities. In this present study, the antioxidant properties of three cleomiscosins were investigated with a focus on the structure-activity relationship using thermodynamic and kinetic calculations with the M06-2X/6-311++G(d,p) method. The results show that CMs, including CMA, CMB, and CMC, are weak antioxidants in apolar environments, with k overall of 7.52 × 102 to 6.28 × 104 M-1 s-1 for the HOO˙ radical scavenging reaction in the gas phase and 3.47 × 102 to 6.44 × 104 M-1 s-1 in pentyl ethanoate. Remarkably, the difference in the fusion of phenylpropanoid structure with coumarin via two ortho-hydroxyl groups (CMA and CMB) does not cause any noticeable effect on their antioxidant activity, while the presence of a methoxy substitute on the aromatic ring of phenylpropanoid units (CMC) increases the reaction rate to about 61 to 84 times faster than that of CMA. In contrast, the studied CMs exhibit a good antioxidant capacity in polar environments, with a k overall range from 4.03 × 107 to 8.66 × 107 M-1 s-1, 102-103 times faster than that of Trolox, equal to that of ascorbic acid and resveratrol. The angular fusion of the phenylpropanoid and coumarin structures, as well as the methoxy substitution on the aromatic ring of the phenylpropanoid unit of the studied CMs, do not have any considerable effect on their antioxidant activity under the studied conditions.

Site-Selective Deuteration of α-Amino Esters with 2-Hydroxynicotinaldehyde as a Catalyst.

An efficient method has been developed for the synthesis of α-deuterated α-amino esters via hydrogen isotope exchange of α-amino esters in D2O with 2-hydroxynicotinaldehyde as a catalyst under mild conditions. This methodology exhibits a wide range of substrate scopes, remarkable functional group tolerance, and affording the desired products in good yields with excellent deuterium incorporation. Notably, the ortho-hydroxyl group and the pyridine ring of the catalyst play a crucial role in the catalytic activity, which not only stabilizes the carbon-anion intermediates but also enhances the acidity of the amino esters' α-C-H bond.

A derivative of trihydroxynaphthalenone and a pyrone metabolite from the endophytic fungus Talaromyces purpurpgenus

A newly discovered trihydroxynaphthalenone derivative, epoxynaphthalenone (1) involving the condensation of ortho-hydroxyl groups into an epoxy structure, and a novel pyrone metabolite characterized as pyroneaceacid (2), were extracted from Talaromyces purpurpgenus, an endophytic fungus residing in Rhododendron molle. The structures of these compounds were elucidated through a comprehensive analysis of their NMR and HRESIMS data. The determination of absolute configurations was accomplished using electronic circular dichroism (ECD) calculations and CD spectra. Notably, these recently identified metabolites exhibited a moderate inhibitory activity against xanthine oxidase (XOD).

Novel Zr-based MOF with Ortho-hydroxyl group selectively traps germanium from aqueous media

Recovery of Ge(IV) from solution is of increasing interest. A novel metal–organic framework adsorbent (Ma-Zr-MOF) is synthesized using mucic acid. A series of characterizations prove the successful synthesis of Ma-Zr-MOF. The maximum adsorption capacity of germanium by Ma-Zr-MOF is 82.06 mg/g at 298 K and pH 6.0, which is better than some of the previously reported adsorbents. The adsorption of germanium ions by Ma-Zr-MOF is in accordance with the pseudo-second-order kinetics and Langmuir isothermal models, the adsorption type is single-layer chemical adsorption on a uniform surface. Thermodynamic calculations yield that the adsorption process is endothermic and spontaneous. Ma-Zr-MOF has good selectivity and anti-interference, and maintains repeatability after five adsorption and desorption cycles. Based on the experimental analysis and density functional theory (DFT) calculations, it is concluded that the Ortho-hydroxyl group played an important role in the adsorption of germanium and that the adsorption mechanism included chelation and ion exchange. In conclusion, Ma-Zr-MOF is proved to be a feasible material for the recovery of Ge(IV) from aqueous media.

Tailoring chelating sites in two-dimensional covalent organic framework nanosheets for enhanced uranium capture.

In this study, we intricately designed and synthesized two isoreticular two-dimensional covalent organic framework nanosheets, namely TAPA-COF-1 and TAPA-COF-2, distinguished by their unique spatial arrangement of hydroxyl groups. These precisely engineered nanosheets were employed as a tailored platform for the selective capture of uranium, due to their tunable chelating sites and characteristic sheet-like morphology. Notably, TAPA-COF-1, featuring ortho-hydroxyl groups, demonstrated a significantly enhanced adsorption capacity for uranium capture originating from the additional oriented adjacent phenolic hydroxyl chelating sites in comparison to TAPA-COF-2 with para-hydroxyl groups, which was proved by theoretical calculation. The impressive features of TAPA-COF-1, including its notable selectivity, rapid adsorption kinetics, and high uptake capacity (657.2 mg g-1), endow it as a highly promising candidate for uranium capture.

Luminescence covalent organic frameworks for metal ions detection via turntable sites

In recent years, environmental issues have been caused by heavy metals, which have not been effectively resolved. Fluorescent materials are being used as promising detectors. Covalent organic frameworks (COFs) possess excellent porosity that provides extensive space for guest molecule. The turntable skeleton is also a crucial factor in designing the target site for capturing them. In this study, the hydrazone-based crystalline H–COF-1 and H–COF-2 were successfully synthesized through a solvothermal process. Their luminescence activities are controlled from blue to green for H–COF-1 and H–COF-2 due to the turntable conjugated sites on the walls. More specifically, the intramolecular hydrogen between the ortho-hydroxyl group and imine bond constructs the conjugations binding site of H–COF-2. H–COF-2 possesses more interacted sites for metal ions and demonstrates efficient fluorescence quenching for Cu2+ at 85 % in water, surpassing the performance of H–COF-1. The selectivity and detection limits were also significantly improved as a result. The turntable sites present a novel design approach for luminescent materials as chemical sensors.

Effect of pendant ester groups on gas transport property of 6FDA-BAPP/6FAP copolyimide membrane

Despite the various methods that have been developed, controlling the microstructure of polyimide membranes to achieve excellent separation performance based on target gases remains a challenge. One such method involves rearranging polyimides containing ortho-hydroxyl groups into polybenzoxazoles at temperatures above 400 °C, which can effectively distort the backbones and improve gas diffusion. However, this approach is limited by the extremely high conversion temperatures required and low conversion degrees achieved. The esterification process of the polyimide, which contains ortho-hydroxyl groups to the imide ring, represents a simple and effective approach to enhance the membrane's competitiveness in gas separation without undergoing thermal rearrangement at high temperatures. The polyimide was prepared by the polycondensation of 4,4'-(Hexafluoro isopropylidene) diphthalic anhydride (6FDA), 2,2-double (4,4-amino phenoxy) propane (BAPP), and 2,2-bis(3-amino-4-hydroxyphenyl)-hexafluoropropane (6FAP). Microstructures and gas transport coefficients were analyzed when the esterification of 6FDA-BAPP/6FAP was conducted using acetic anhydride and caproic anhydride. In CO2/N2 separation, a-6FDA-BAPP/6FAP exhibits CO2 permeability of 1279.41 ± 66.93 Barrer and perm-selectivity of 40.80 ± 2.27, owing to the significantly improved affinity to CO2. The membrane of c-6FDA-BAPP/6FAP exhibit the further improved CO2 permeability and deteriorated perm-selectivity, due to a leveling effect on the diffusion of CO2 and N2 caused by the pendant caproates with longer alkyl chains. The results confirmed that the gas separation performance of polyimide membrane containing ortho-hydroxyl groups is sensitive to the pendant group.

Gene-Directed Generation of Unprecedented Bioactive Compounds

Bioactive compounds with previously undescribed frameworks are highly desired for the discovery and development of new drugs and agrochemicals, but very few attempts have been reported to generate such molecules in biological contexts. Here, we present a gene-directed generation of architecturally unprecedented polyketide–indole hybrids (PIHs), which was conceptualized and materialized by employing polyketide synthases expressed in a heterologous vector, with simultaneous exposure to exogenous chemicals. To make an exemplification to this generally applicable approach, the ChrA and ChrB genes of Daldinia eschscholzii IFB-TL01 were integrated into the Aspergillus oryzae (AO) cell, and the resultant ChrA/ChrB-AO transformant was cultured in the indole-3-carbinol (I3C)-supplemented medium, leading to the production of seven skeletally undescribed PIHs named aochrabines A–G. Among them, aochrabines A–C exhibited a broad spectrum in inhibiting the growth of Gram-positive bacteria, whereas aochrabines B, C, and G showed moderate antitumor activities. Unexpectedly, the construction of such aochrabine molecules was achieved by the regioselective Michael addition of 3-methyleneindolium (3MI, generated from I3C in the AO culture) to different polyketide precursors with the yields (much) higher than those in the D. eschscholzii culture where comparable. Chemically, the benzyl-methine carbons in the precursor molecules were found to be made more vulnerable to the 3MI attack by the hydrogen-bonding between the ortho-hydroxyl and meta-carbonyl groups. Collectively, this is the first report of the ortho- and meta-substituent co-driven regioselective Michael addition of electrophilic methylene compounds to heterologous PKS production platform to in situ multiply the chemodiversity of microbial cultures, thus showing great potential in producing valuable compounds with new chemical space.

The binding mechanism of benzophenone-type UV filters and human serum albumin: The role of site, number, and type of functional group substitutions

Benzophenone-type UV filters (BPs) are common in natural aquatic environments. They can cause endocrine disruption or other adverse effects once they enter the human body via the food chain or drinking water. The primary cause of BPs accumulation and toxicity is the transport of BPs into the human body. Functional group substitutions can have a significant impact on the interactions of BPs and transporters, resulting in a variety of impact effects. Therefore, we explored the interaction between human serum albumin (HSA, a typical transporter) and ten typical BPs [benzophenone (BP1), 2-hydroxybenzophenone (BP2), 4-hydroxybenzophenone (BP3), 2,2′-dihydroxybenzophenone (BP4), 2,4-dihydroxybenzophenone (BP5), 4,4′-dihydroxybenzophenone (BP6), 2,4,4′-trihydroxybenzophenone (BP7), 2,2′,4,4′-tetrahydroxybenzophenone (BP8), 2-hydroxy-4-methoxybenzophenone (BP9), and 2,2′-dihydroxy-4-methoxybenzophenone (BP10)] to study the role of functional group substitutions in binding. The results showed that BPs could bind to HSA at site 2, with binding constants ranging from 2.01 × 103 to 4.57 × 105 L/mol. Compared to BP1, hydroxyl and methoxy substitutions enhanced the BPs-HSA binding. The combined effect of the number and site of hydroxyl substitution at BPs determined the binding strength between BPs and HSA. It was more accessible to bind HSA when BPs were substituted with para-hydroxyl (4-hydroxyl) groups than with ortho-hydroxyl (2-hydroxyl) groups. Moreover, the additional para-methoxy (4-methoxy) group increased the BP-HSA binding strength by approximately 47 times under the same hydroxyl substitution conditions. Theoretical calculations revealed that functional group substitutions increased the intermolecular binding force by increasing the negative electrostatic potential surface area of BPs, which significantly increased the electrostatic and dispersion forces between the BPs and HSA. This BPs-HSA binding decreased the α-helix of HSA and influenced the ratio of other secondary structures, including β-sheet, β-turn, and random coil of HSA. This study provides a theoretical and experimental foundation for understanding the human health risks associated with BPs.

Synthesis of some new 2-mercaptobenzoxazol and study their biological activity against some plant pathogenic fungi

The research included synthesis of 2-mercapto benzoxazole (MBO) (1) ) from the reaction of ortho hydroxyl aniline with carbon disulfide in ethanolic potassium hydroxide. The hydrazine benzoxazole HMBA2 (2) was synthesized from the reaction of compound MBO (1) with hydrazine hydrate in presence of alcohol. Compounds (3(a- e)) were synthesized by condensate on of substituted Benzaldehydes with 2-Hydrazino benzoxazole HMBA2. The Ethyl2-(benzoxazolylthio) acetate EMBA1 (4) obtained from the reaction of compound MBO (1) with solution of ethyl chloro acetate using KOH alcoholic .Finally the compound hydrazide HMBA(5 (a- e)) was synthesized from the reaction of compound (4) with hydrazine hydrate in presence of alcohol .All these synthesized compounds were characterized on the basis of their 1H-NMR ,IR, The study is Showed biological activity for chemical compounds, at three concentration 100, 200, 300 ppm in toxic potato Dextrose Agar (PDA) medium method against phytopathogenic fungi three species Fusariumgraminarium, Sclerotiniasclerotium and Rhizoctoniasolani, its isolation on nutritious PDA medium from root plants wheat ,eggplant and cotton continually, diameter measure of fungi growth colony result showed all compound growth inhibition barring MMBA compound non effective inhibition its, appear MBO moral superiority after bring HMBA2 both induce inhibition amount 49.69 and 34.22% continually. Compound concentration its average effect result reveal third significant superior on first and second concentration, interference effect concentration and species chemical compound notice higher inhibition amount 100%with third concentration MBO compound all test its fungi .

Synthesis and evaluation of small organic molecule as reactivator of organophosphorus inhibited acetylcholinesterase

A series of uncharged salicylaldehyde oximes were synthesized and evaluated for the reactivation of organophosphorus (OP) nerve agents simulants Diethylchlorophosphonate (DCP) & Diethylcyanophosphonate (DCNP) and pesticides (paraoxon & malaoxon) inhibited electric eel Acetylcholinesterase (AChE). The computational software Swiss ADME and molinspiration were used to unfold the probability of drug-likeness properties of the oximes derivatives. Substituted aromatic oximes with diethylamino or bromo group with free hydroxyl group ortho to oxime moiety were found efficient to regenerate the enzymatic activity in in-vitro AChE assay. The alkylation of the ortho hydroxyl group of derivatives led to the loss of reactivation potential. The derivatives with a hydroxyl group and without oxime group and vice versa did not show significant reactivation potency against tested OP toxicants. Further, we also evaluated the reactivation potential of these selected molecules on the rat brain homogenate against different OPs inhibited ChE and found maximum reactivation potency of oxime 2e. The in-vitro results were further validated by molecular docking and dynamic studies which showed that the hydroxyl group interacted with serine amino acids in the catalytic anionic site of AChE enzyme and was stable up to 200 ns consequently providing proper orientation to oxime moiety for reactivating the OP inhibited enzyme. It has thus been proved by the structure-activity relationship of oximes derivatives that hydroxyl group ortho to oxime is essential for reactivating OP inhibited electric eel AChE. Amongst the twenty-one oximes derivatives, 2e was found to be most active in regenerating the paraoxon, malaoxon, DCP and DCNP inhibited AChE enzyme.

Organic dyestuff modifier enhancing energy storage performance of PEI-based nanocomposites

In recent years, with the increasing demand for power supply in harsh environments, high temperature-resistant dielectrics have attracted more and more attention. However, polymer-based composites with high glass-transition-temperature polymers still suffer fillers’ homogeneous dispersion problems. In this work, polyetherimide (PEI)-based nanocomposites filled with modified BT nanoparticles were designed and prepared. The surface modifier is an organic dye, celestial blue, which contains ortho-hydroxyl functional groups capable of chelating with metal oxides and a conjugated molecular structure that is well compatible with the PEI polymer matrix. The nanocomposites mBT/PEI exhibit improved dielectric and energy storage performance. At 2 vol%, the maximum energy density reaches 4.2 J cm−3, which was 31 % higher than that of the nanocomposite BT/PEI without surface modification.

Inhibitory activities of flavonoids from Scutellaria baicalensis Georgi on amyloid aggregation related to type 2 diabetes and the possible structural requirements for polyphenol in inhibiting the nucleation phase of hIAPP aggregation

Human islet amyloid polypeptide (hIAPP)-mediated cytotoxicity is identified as a potential target for developing new anti-diabetic molecules. Herein, we investigated the effect of the major bioactive compounds of Scutellaria baicalensis Georgi (S. baicalensis), including baicalein, baicalin, wogonin and oroxylin A, on hIAPP aggregation. We found that all of these compounds inhibited hIAPP fibril formation in a dose-dependent manner. But baicalein and baicalin, especially baicalein are more effective than wogonin and oroxylin A in stabilizing hIAPP monomers and eliminating toxic hIAPP assembly, suggesting that flavonoids with ortho-hydroxyl group on the A-ring exhibited higher anti-hIAPP nucleation potential than those without this structure. This stimulated our interest in further studying the possible structure-activity relationship between polyphenol and hIAPP aggregation inhibition. Our results demonstrated that flavonoids with ortho-hydroxyl group on the B-ring are also more effective against hIAPP nucleation than those without this structure. These results suggest that the ortho-hydroxybenzene structure is a key structural feature required for polyphenols to effectively inhibit hIAPP nucleation. This was further confirmed by the effects of polyphenol and phenols in inhibiting hIAPP nucleation. The conclusion that pyrogallol-type polyphenols are potential lead inhibitors may provide a valuable structural template for the further development of polyphenol-based inhibitor of amyloid peptides.

Thermally rearranged poly(benzoxazole-co-imide) composite membranes on α-Al2O3 support for helium extraction from natural gas

Membrane gas separation is deemed as the most energy-efficient approach to extract the rare He from natural gas. However, the techno-economic feasibility was far from the practical application because of the poor separation performance illustrated by Robeson's upper bound. Herein we reported a high-performance polymeric membrane for He extraction from natural gas. Besides the bulky Cardo segments, the pristine polymeric backbone was featured with reactive ortho-hydroxyl groups, which were thermally rearranged to benzoxazole rings benefitting micropore formation. The polymer was well dissolved in NMP then facilely coated on α-Al2O3 support for further thermal rearrangement. The thin and selective membrane showed He permeance of 40 GPU and He/CH4 mixture selectivity of 74 surpassing the benchmark membranes for helium extraction. Mitigation of physical aging was demonstrated by the long-term (>1000 h) separation in He/N2 and He/CH4 binary mixtures. The excellent He separation performance and anti-aging property endowed the membrane appealing to practical He extraction from natural gas.

Flavonoids and proanthocyanidins-rich fractions from Eugenia dysenterica fruits and leaves inhibit the formation of advanced glycation end-products and the activities of α-amylase and α-glucosidase

Ethnopharmacological relevanceDifferent parts of Eugenia dysenterica have been popularly used in Brazil for treating diabetes mellitus and its complications. The present study aimed to screen extracts from E. dysenterica fruit pulp, peel, seed and leaf for carbohydrate digestive enzymes inhibitors with antioxidant and anti-glycation capacities. Materials and methodsEthanol extracts of E. dysenterica were subjected to a liquid-liquid fractionation and the fractions were used to evaluate their antioxidant properties and inhibitory potential against the formation of advanced glycation end-products (AGEs) and α-amylase and α-glucosidase. ResultsThe ethyl acetate fraction (EtOAcF) from seed and the dichloromethane fraction (CH2Cl2F) and EtOAcF from leaf had high antioxidant capacities (ORAC >5500 μmol trolox eq g-1, FRAP >1500 μmol trolox eq g-1 and DPPH IC50 < 35 μg mL-1) and showed exceptional inhibitory activities against AGEs formation (glycation inhibition above 80% at 10 μg mL-1) and α-amylase and α-glucosidase (inhibition above 50% at 10 μg mL-1). The gallated B-types proanthocyanidins were the most active ingredients found in the leaf of E. dysenterica (CH2Cl2 and EtOAcF), being responsible for the notorious inhibitory effects against glycation and glycoside hydrolases due to their ortho-hydroxyl groups, which play role in scavenge and quench free radicals and glycated products, and may occupy the enzymes’ substrate binding pocket. Furthermore, gallic acid, quercetin and its glycoside derivatives were detected by the first time in the E. dysenterica fruit seed (EtOAcF). ConclusionsThe results strongly contribute to the understanding of the antidiabetic potential of seeds and leaves from E. dysenterica, a species from a global biodiversity hotspot, which appears to be linked to the prevention of oxidative stress, AGEs production and postprandial hyperglycemia.

Theoretical (DFT) and experimental (FT-IR & FT Raman) approach to investigate the molecular geometry and vibrational properties of 2,5- and 2,6-dihydroxytoluenes

Fourier Transform infrared spectra were measured for 2, 5- dihydroxytoluene (5DHT) and 2, 6- dihydroxytoluene (6DHT), in the spectral range 4000–400 cm−1. Fourier Transform Raman spectra were also recorded for the same molecules, in the spectral region 3500–100 cm−1. Torsional potential energy scans were attempted around ring – ortho hydroxyl C-O bonds, and ring-methyl C-C bond, for the two molecules. Barrier heights were computed for the above bonds for both the target molecules. Optimized molecular geometry, general valence force constants, vibrational wave numbers (harmonic), infrared intensities, and Raman scattering intensities were calculated, employing density functional theory and using B3LYP/6-311++G(d,p) level of formalism. Observed and measured frequencies agreed with an rms error 8.6 and 8.3 cm−1, for 5DHT and 6DHT, respectively, on scaling. In addition, experimental infrared and Raman spectra agreed with their simulated counterparts with good accuracy. Using potential energy distribution (PED) and eigenvectors, all fundamentals were assigned unambiguously for both molecules. Geometry optimization was made for trimers of the two molecules at the same level of theory as used for the monomers. Existence of inter-molecular hydrogen bond was predicted.

Synthesis and properties of organoboron functionalized nanocellulose for crosslinking low polymer fracturing fluid system.

The traditional organoboron crosslinker used in the guar gum fracturing fluid has the disadvantages of a larger amount of guar gum and crosslinker and higher susceptibility to pH. Nanoparticles have special properties such as large specific surface area and many active groups, so the organic boron crosslinker and nanoparticles are combined to obtain nano crosslinkers. In this paper, rod-shaped nano-cellulose particles were prepared by acid hydrolysis, and a nanocellulose crosslinker was synthesized by combining with organic boron and KH550. Nanocellulose cross-linker has good temperature and salt resistance. It can meet the requirements of cross-linking guar gum fracturing fluid with a mass fraction of 0.3 wt% under neutral conditions. The residual viscosity is higher than 50 mPa s under shear at 170 s−1 and 110 °C for 60 minutes when the pH increases from 7 to 13, and NBC crosslinking can withstand a temperature of 160 °C under pH = 10. The crosslinking mechanism of the widely accepted nano-crosslinker is that the organoboron on the surface of the nanoparticle combines with the homeopathic ortho hydroxyl of the guar gum molecule to form a hydrogen bond and thereby form a complex network structure. This research shows that the hydrogen bonding between the nano-cellulose crosslinker and HPG molecules, and the resulting gel has a more complex network structure because of the formation of inter-chain cross-links.

Natural polyphenols enhanced the Cu(II)/peroxymonosulfate (PMS) oxidation: The contribution of Cu(III) and HO•

Copper ion (Cu(II)) in water or wastewater has been reported to trigger peroxymonosulfate (PMS) oxidation of organic contaminants (OCs). However, this process can only work in alkaline condition, which limits its potential application. In this study, we found that the introduction of natural polyphenols in the Cu(II)/PMS process can significantly promote the degradation of tetrabromobisphenol A (TBBPA), one of the most widely used brominated flame retardants, in the pH range of 4.3−9.0. With gallic acid (GA) as a representative natural polyphenol, the degradation of TBBPA by GA/Cu(II)/PMS process reached 84.6% in 10 min at initial pH of 4.3 (without pH adjustment), which was 2.2 times higher than that by Cu(II)/PMS process. Multiple reactive oxidants, including Cu(III), hydroxyl radical (HO•) and singlet oxygen, were generated in this process among which Cu(III) and HO• contributed to TBBPA degradation with Cu(III) playing the dominant role. GA accelerated the reduction of Cu(II) to Cu(I) due to the strong chelation and electron-donating capacity of ortho-hydroxyl groups in GA, and then Cu(I) was quickly oxidized by PMS to Cu(III) which can be further acid-catalyzed to produce HO•. TBBPA transformation mainly proceeded through electron abstraction, oxidative debromination and ring-opening reaction pathways. The feasibility of in-situ utilizing natural organic matter (NOM, enriched with polyphenol moieties) to accelerate the degradation of TBBPA by Cu(II)/PMS process in surface water and wastewater was confirmed. The findings of this study indicate that the coupling of NOM and Cu(II), which are present in contaminated water or wastewater, can potentially improve PMS oxidation of OCs in a wide range of pH.

Synthesis and characterization of a novel soluble hesperetin monoglucoside-copper(Ⅱ) complex using ion exchange column

The coordination of flavonoids with metal ions often improve the biological activity of flavonoids. In this study, an integrated method using ion exchange column for the synthesis of the hesperetin monoglucoside-copper(Ⅱ) complex (the HMG-Cu(Ⅱ) complex) was investigated. The integration including the separation and the coordination reaction of HMG was studied firstly. The stoichiometric ratio of the complex was studied by the method of equimolar solutions and the molar ratios. The compound structures were characterized by theoretical quantum chemical calculation, elemental analysis, ultraviolet–visible (UV–Vis) spectra analysis, Fourier transform infrared (FT-IR) spectra analysis, X-ray diffraction (XRD) patterns analysis, scanning electron microscope (SEM) and thermal methods (TG/DSC) analysis. Results showed that both the carboxyl group and its ortho hydroxyl group in hesperetin monoglucoside (HMG) participated in the coordination reaction. The D296 strong basic anion exchange resins could effectively adsorb HMG. The static adsorption equilibrium time was 20 h and equilibrium data fitted better to the Langmuir model than Freundlich model. The adsorption process was a monolayer adsorption process on homogenous surface of D296 resins and the fitting of the pseudo-second-order model was better. The metal-to-ligand ratio was 1:2. In addition, the complex was greatly affected by pH, the stablest at pH 8.0. So, this research offered a feasible pathway of getting a high value-added complex of HMG-Cu(Ⅱ).