Catalytic Oxidation Of Sulfides Research Articles

Bimetallic homoleptic divalent metal-complexes of diisatin dihydrazone ligand. Biological activity and catalytic oxidation of sulfides

According to the significant role of transition metals in their metallo-organic frameworks catalytically and biologically, two new dinuclear homoleptic complexes of Pd2+ and VO2+ ions (PdLC2 and VOLC2, respectively) with succinyl dihydrazone diisatin ligand (H2LC2) were constructed. The effect of the M2+ ion type was distinguished in the productive redox protocol of diphenyl sulfide (DiPhS) and methylphenyl sulfide (MePhS) within H2O2. Considerable productivity was assigned by the yielding percentages of diphenyl sulfoxide (DiPhSO) and methylphenyl sulfoxide (MePhSO) (the mono-oxo-selective product) catalyzed by PdLC2 or VOLC2, in which VOLC2 catalyst exhibited little more classified efficiency than that of PdLC2, referring to the progressed redox potential of V4+ ion in VOLC2 catalyst.Their biological performance was recorded based on their inhibited potential against the growing power of some cancer/normal cells of humans, bacteria, as well as, fungi. The bio-studies appointed the role and job of M2+ ion (Pd2+ or VO2+ ion) in its chelated MLC2 complex over the free ligand, H2LC2. Moreover, their interacted modes with ctDNA (i.e. calf thymus DNA) were examined via the viscometries and spectrophotometric titration. Since the two chelates (PdLC2 and VOLC2) represented an attractive performance for the inhibited action for the current microorganisms and the cancer cell lines of humans’ growth over the free H2LC2 ligand. PdLC2 and VOLC2 complexes displayed an appreciable reaction with ctDNA more than that of their free organo-ligand H2LC2. From the binding constant (Kb) and Gibb’s free energy (ΔGb≠) values, both PdLC2 and VOLC2 exhibited more binding interaction within ctDNA than that of the H2LC2 ligand, with the progressed Lewis acidity, electronegativity, and lipophilic feature (hydrophobicity).

SOD1 is an essential H2S detoxifying enzyme

Although hydrogen sulfide (H2S) is an endogenous signaling molecule with antioxidant properties, it is also cytotoxic by potently inhibiting cytochrome c oxidase and mitochondrial respiration. Paradoxically, the primary route of H2S detoxification is thought to occur inside the mitochondrial matrix via a series of relatively slow enzymatic reactions that are unlikely to compete with its rapid inhibition of cytochrome c oxidase. Therefore, alternative or complementary cellular mechanisms of H2S detoxification are predicted to exist. Here, superoxide dismutase [Cu-Zn] (SOD1) is shown to be an efficient H2S oxidase that has an essential role in limiting cytotoxicity from endogenous and exogenous sulfide. Decreased SOD1 expression resulted in increased sensitivity to H2S toxicity in yeast and human cells, while increased SOD1 expression enhanced tolerance to H2S. SOD1 rapidly converted H2S to sulfate under conditions of limiting sulfide; however, when sulfide was in molar excess, SOD1 catalyzed the formation of per- and polysulfides, which induce cellular thiol oxidation. Furthermore, in SOD1-deficient cells, elevated levels of reactive oxygen species catalyzed sulfide oxidation to per- and polysulfides. These data reveal that a fundamental function of SOD1 is to regulate H2S and related reactive sulfur species.

Novel oxo–peroxo W(VI) Schiff base complex: synthesis, SC-XRD, spectral characterization, supporting on chloromethylated polystyrene, and catalytic oxidation of sulfides

Novel oxo–peroxo W(VI) Schiff base complex: synthesis, SC-XRD, spectral characterization, supporting on chloromethylated polystyrene, and catalytic oxidation of sulfides

Effective anodic sulfide removal catalyzed by single nickel atoms on nitrogen-doped graphene with stainless steel substrate

Hydrogen sulfide is hazardous and life-threatening gas emission in anaerobic digestion and degradation. Electro-oxidation technology is a promising process for sulfide removal in aqueous media due to its high efficiency, cost effectiveness and easy operation. This study employed atomic nickel dispersed on nitrogen-doped graphene catalyst (A-Ni-NG) with stainless steel (SS) substrate for efficient sulfide removal. The results showed that the highest sulfide removal efficiency of 85.02±1.25% was achieved on SS/A-Ni-NG anode at 1.98 V (vs. RHE) in 48 h, which was 11.17% and 24.18% higher than that of bare SS and FTO/A-Ni-NG, respectively. SS/A-Ni-NG catalyst achieved a first-order rate constant of 0.036±0.001 h−1, improved by 24% compared with bare SS. The main products of sulfide oxidation were thiosulfate and elemental sulfur with Faradic efficiency of 32.37±3.20% and 18.99±0.05%, respectively. Electrochemical analysis showed the sulfide oxidation anodic peak potential on SS/A-Ni-NG anode was 280 mV (vs. RHE), lower than most of the reported graphite or Ni anodes. SS/A-Ni-NG improved the interface electric conductivity and the charge transfer rate, and directly catalyzed sulfide oxidation at applied voltage below oxygen evolution reaction (OER) onset potential. A-Ni-NG also indirectly removed sulfide by boosting OER at higher voltage. The superior sulfide oxidation catalytic activity of SS/A-Ni-NG anode was mainly attributed to the atomic dispersed Ni(I) generating NiOOH that boosted OER process and to the dopant N that induced activation region. A-Ni-NG coated on SS substrate is demonstrated to be a promising material for electrochemical sulfide removal.

Protein engineering of thioether monooxygenase to improve its thermostability for enzymatic synthesis of chiral sulfoxide

• Consensus analysis and random mutagenesis were conducted to engineer a cyclohexanone monooxygenase from the Acinetobacter calcoaceticus (AcCHMO-M6) for improving its thermostability as well as specific activity. • The half-lives of the resultant mutants at 40 °C were increased up to 8.5 h as well as with up to 4-fold enhance in specific activity. • By employing the best mutant AcCHMO-M10, complete conversion (>99% conversion, >99% ee) asymmetric Kagan oxidation of omeprazole sulfide was achieved in 16 h, while the AcCHMO-M6 only afford 39% conversion. Esomeprazole, the S -enantiomer of omeprazole, is the best-selling proton pump inhibitor. In our previous work, a mutant of cyclohexanone monooxygenase from the Acinetobacter calcoaceticus (named Ac CHMO-M6) was successfully obtained through protein engineering which could catalyze the oxidation of omeprazole sulfide. However, its practical application is still hindered by the poor thermostability, especially in the up-scaled reaction process. In this work, site mutagenesis based on consensus analysis and directed evolution were used to engineer this enzyme in order to improve the stability of Ac CHMO-M6. The half-lives of the resultant mutants Ac CHMO-M9 (F29L/R444E) and Ac CHMO-M10 (F29L/R444E/A145S/G430T) at 40 °C were increased from 2.2 h to 8.5 h and 5.9 h respectively, while the corresponding T m values were increased by 7 °C and 5.3 °C in comparison to Ac CHMO-M6. The specific activity of Ac CHMO-M9 was comparable to that of Ac CHMO-M6, and the specific activity of Ac CHMO-M10 was about 4-fold that of Ac CHMO-M6. The Ac CHMO-M10 catalyzed sulfide oxidation reaction reached 100% conversion after 16 hours at 30 °C, in contrast to 39.4% conversion in the case of Ac CHMO-M6. These results show that the potential of this thioether monooxygenase can be significantly improved by protein engineering.

Visible light generation of chromium(V)-oxo salen complexes and mechanistic insights into catalytic sulfide oxidation

Visible light irradiation of the photo-labile salen-chromium(III) chlorate or bromate precursors produced salen-chromium(V)-oxo complexes that were spectroscopically and kinetically indistinguishable from those formed by chemical oxidation of chromium(III) salens with PhI(OAc)2. The photochemistry observed in this work is ascribed to the heterolytic cleavage of the O-X bond in the apical counterion that results in a two-electron oxidation of the metal to form the chromium(V)-oxo species. Second-order rate constants for oxidation reactions of 3 with organic substrates were determined under pseudo-first order condition, and particularly low level of reactivity for sulfide oxidations was observed. In this study, chromium(III) salen complexes effectively catalyzed the oxidation of aryl sulfides into sulfoxides with PhI(OAc)2 in the presence of a small amount of water. The competition product studies with the Hammett correlation plot indicated that the observed chromium(V)-oxo species is not likely to serve as the major oxidant for the sulfide oxidations catalyzed by chromium(III) salens with PhI(OAc)2.

A novel binuclear iron(III)-salicylaldazine complex; synthesis, X-ray structure and catalytic activity in sulfide oxidation

A novel binuclear iron(III)-salicylaldazine complex has been synthesized and characterized by various techniques such as IR and UV–Vis spectroscopy and X-ray crystallography. The catalytic oxidation of sulfides in the presence of the aforementioned complex was explored at room temperature using urea hydrogen peroxide (UHP) as an oxidant. Effects of different reaction conditions consisting catalyst and oxidant amount, solvent effect and reaction time on the catalytic activity and selectivity in the reaction of methylphenylsulfide oxidation has been surveyed. Perfect selectivity toward sulfoxide was achieved after 15 min in CH3CN by choice of a properly optimized reaction condition.

Synthesis of Two-dimensional Hydrophobic Copper-based Nanosheets and Their Application in Catalytic Oxidation of Sulfides

Two-dimensional nanomaterials have received extensive attention because of their unique physicochemical properties. However, bottom-up synthesis of two-dimensional (2D) stable nanomaterials still remains great challenge. In this work, a novel 2D metal-organic (Cu-BDT) nanosheet is constructed at room temperature by coordinative self-assembly, namely, using monovalent copper ion as the metal precursor and 1,4-benzenedithiol as organic ligand. As-synthesized Cu-BDT nanosheets are fully characterized by various techniques including powder-diffraction of X-rays (P-XRD), Fourier transform infrared spectrometer (FT-IR), Raman spectra (Raman), scanning electron microscopy (SEM), transmission electron microscope (TEM), atomic force microscope (AFM), X-ray photoelectron spectroscopy (XPS), inductively coupled plasma optical emission spectrometer (ICP-OES) and contact angle test. The catalytic result verifies that the Cu-BDT nanosheet surfaces possess abundant active sites and good hydrophobicity, which facilitate oxidation of sulfides into sulfoxide compounds.

Lewis Acid Dominant Windmill-Shaped V8 Clusters: A Bifunctional Heterogeneous Catalyst for CO2 Cycloaddition and Oxidation of Sulfides.

Carbon dioxide (CO2) and sulfides in gasoline are the main causes of air pollution. Considerable attention has been devoted to solving the problems, and the catalytic reaction seems to be a good choice. Owing to the high density of Lewis acid (LA) active sites and large numbers of open methoxide groups, polyoxovanadates (POVs) are an undisputed option as a heterogeneous catalyst for the CO2 cycloaddition reaction and catalytic oxidation of sulfides. On the basis of the above, a series of V8 clusters, [(C2N2H8)4(CH3O)8VIV8O12]·CH3OH (V8-1a), [(C2N2H8)4(CH3O)4VIV4VV4O16]·4CH3OH (V8-1), [(C3N2H10)4(CH3O)4VIV4VV4O16]·5H2O (V8-2), [(C6N2H14)4(CH3O)4VIV4VV4O16]·5CH3OH·2H2O (V8-3), have been legitimately designed and triumphantly isolated. In the synthesis process, three different kinds of Lewis bases (LBs), ethanediamine, 1,2-diaminopropane, and 1,2-cyclohexanediamine, were used to modify LA {V8} clusters to form four diverting windmill-shaped configuration. Among them, the vanadium atoms in V8-1a are +4 valence of VIV, while the vanadium atoms in V8-1-3 are mixed valence states of VIV and VV. Magnetic property investigation indicates that the antiferromagnetic coupling interactions between VIV ions all exist in the four compounds. The compound V8-1 also demonstrated high catalytic activity in the cycloaddition of CO2 to several epoxides under relatively mild conditions (70 °C, 0.5 MPa). More importantly, the reaction pressure 0.5 MPa is the lowest among the high nuclear polyoxometallates (POMs). Furthermore, V8-1 also has an excellent catalytic conversion for the oxidation of sulfides. The catalytic tests manifested that V8-1 was a very efficient difunctional heterogeneous catalyst for CO2 cycloaddition reaction and catalytic oxidation of sulfides.

Investigation of 3,3′,5,5′-tetra-tert-butyl-4,4′-stilbenequinone-based catalyst in the reaction of liquid-phase oxidation of inorganic sulfides

ABSTRACTIn this paper, the intermediate and final reaction products of catalytic oxidation of inorganic sulfides in the presence of oxygen dissolved in the kerosene fraction and 3,3′,5,5′-tetra-tert-butyl-4,4′-stilbenequinone were investigated. The thiosulfate and sulfate are major products of the oxidation of sodium sulfide under these conditions. The intermediate and final products in the catalytic oxidation of sulfide sulfur do not affect the rate of its oxidation. The yield of catalytic oxidation products depends on the nature of the sulfide and on the pH of the solution. The catalytic cycle for sulfide oxidation in the presence of 3,3′,5,5′-tetra-tert-butyl-4,4′-stilbenequinone is shown. The role of 3,3′,5,5′-tetra-tert-butyl-4,4′-stilbenequinone is to create a new and a more effective way of electron transfer from the reducing agent (sulfide) to the oxidant (oxygen).

Mo(vi) complex supported on Fe3O4 nanoparticles: magnetically separable nanocatalysts for selective oxidation of sulfides to sulfoxides

A molybdenum complex was immobilized on amino propyl and Schiff base modified magnetic nanoparticles by covalent linkage. In catalytic oxidation of sulfides, the catalysts showed similar catalytic activity but different stability and recyclability.

Highly selective and efficient oxidation of sulfides with hydrogen peroxide catalyzed by a chromium substituted Keggin type polyoxometalate

The catalytic oxidation of sulfides into the corresponding sulfones by a chromium substituted Keggin type polyoxometalate, (TBA)4[PW11CrO39]·3H2O, was achieved using mild reaction conditions. Excellent yields were obtained using four equivalents of 30% H2O2. Under these reaction conditions, the sulfide group was highly reactive and other functional groups such as hydroxyl or a double bond were unaffected. Using a commercially available, eco-friendly, and cheap oxidant, mild reaction conditions, operational simplicity, practicality, short reaction times, high to excellent yields, and excellent chemoselectivity are some of the advantages of this catalytic system.

Oxidation of olefins and sulfides with different oxidants catalyzed by meso-tetra(n-propyl)porphyrinatomanganese(III) acetate: comparison with meso-tetra(phenyl)porphyrinatomanganese(III) acetate

In this study, the catalytic activity of meso-tetra(n-propyl)porphyrinatomanganese(III) acetate, MnT(n-pr)(OAc) in oxidation of olefins and sulfides with tetra-n-butylammonium Oxone (TBAO), tetra-n-butylammonium periodate (TBAP), aqueous hydrogen peroxide, sodium periodate and Oxone in the presence of imidazole (ImH) has been studied. The comparison of catalytic performance of MnT(n-pr)P(OAc) and MnTPP(OAc) in oxidation of olefins with TBAP shows that while the latter is four times more efficient than the former, the extent of oxidative degradation of the former is ca. 3.5 times greater than the latter. The use of excess amount of styrene resulted in only a ca. 10 % increase in the catalyst stability, suggesting a mainly intramolecular mechanism for the catalyst degradation. On the other hand, in the case of TBAO, the oxidative degradation of the former is four times greater than the latter, but the catalytic performance of the latter for the oxidation of cyclohexene was only ca. 2 times larger than the former. This observation shows that the decreased catalytic performance of MnT(n-pr)P(OAc) relative to MnTPP(OAc) is essentially due to the high degree of degradation of the former. Due to the high degree of catalyst degradation, oxidation of olefins with periodate and Oxone in the presence of the two manganese porphyrins in aqueous solution (or with hydrogen peroxide in dichloromethane) gave little or no product. Oxidation of sulfides with TBAO and TBAP in the presence of MnT(n-pr)P(OAc) showed a conversion of ca. 15 % for the catalytic oxidation of sulfides to sulfones.

SnO2 Nanoparticles: Preparation and Evaluation of their Catalytic Activity in the Oxidation of Aldehyde Derivatives to their Carboxylic Acid and Sulfides to Sulfoxide Analogs

A variety of aromatic and aliphatic aldehydes were converted to the corresponding carboxylic acid derivatives with 30% H2O2 and tert-butyl hydroperoxide as the oxidant in the presence of a catalytic amount of SnO2 nanoparticles as a precursor. These nanoparticles were also used for the efficient catalytic oxidation of sulfides to sulfoxides using 30% H2O2. The present methodology offers several advantages such as applicability to a wide range of aldehydes/ sulfides, convenient work-up, mild reaction conditions as well as good yields and reasonable time of the reactions. Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file.

Retracted: A new nano bismuth(III) salophen catalyst for green and efficient catalytic oxidation of sulfides into the corresponding sulfoxides

Bismuth(III) salophen as a new catalyst has been synthesized. Structural properties of this complex have been studied by Fourier transform infrared spectroscopy, X-ray diffraction, differential scanning calorimetry, and thermal gravimetric analyses. The average crystalline size of Bi-salophen particles was 86 nm. Thermal analyses show that the complex is stable over 300°C. Catalytic activity of this catalyst has been investigated in oxidation of sulfides. Different kinds of sulfides have been oxidized to the corresponding sulfoxides efficiently in the presence of sodium periodate as oxidant in glacial acetic acid as solvent at room temperature. These sulfides were selectively and completely converted into their corresponding sulfoxides in very short reaction times. Selectivity of this method was excellent, which is another advantage of this method.

New chiral molybdenum complex catalyzed sulfide oxidation with hydrogen peroxide

Six new cis-dioxomolybdenum(VI) complexes of chiral Schiff-base ligands, derived from condensation of various amino alcohols and substituted salicylaldehydes, have been prepared and characterized by NMR, IR, ESI-MS and single crystal X-ray diffraction techniques. The geometry around the molybdenum center is distorted octahedral in which a tridentate Schiff-base ligand with two anionic oxygens and one neutral imine nitrogen occupies meridional position. The octahedral geometry of the cis-dioxomolybdenum center is additionally completed by a coordinated labile solvent molecule. In some complexes the sixth site is found to be vacant where the relatively bulky substituents hinder the coordination of the solvent. These complexes are tested for catalytic enantioselective sulfoxidation reactions using hydrogen peroxide as oxidant at low temperature which shows high selectivity along with good to moderate enantiomeric excess. ESI-MS study of the reaction mixture indicates the formation of oxoperoxoMo(VI) complexes during catalysis. The steric effect originated from the substituent on chiral ligand on the catalytic reaction is also discussed. It is found that the substituents at the β position of the amino alcohol seem to greatly influence the enantioselectivity of the oxidation reactions.

Catalytic oxidation of sulfides to sulfoxides using aluminium hydrogen sulfate, sodium nitrite and catalytic amounts of metal bromide

A catalytic, chemoselective and environmentally friendly procedure for the oxidation of sulfides is described. A wide range of aliphatic or aromatic sulfides were successfully oxidized to the corresponding sulfoxides using NaNO2, Al(HSO4)3 and a catalytic amount of KBr or NaBr in the presence of wet SiO2 (50% w/w) in CH3CN under heterogeneous conditions in moderate to high yields.

Catalytic Sulfoxidation by Dinuclear Copper Complexes

The ability of the copper enzyme tyrosinase to promote oxygen atom insertion into the aromatic C! H bond of phenolic substrates, and also the simpler oxidation of o-diphenols, by O2 [1] has stimulated an enormous number of biomimetic studies based on copper complexes. [2] The enzymatic reactions occur through a key oxygenated intermediate that has been thoroughly characterized spectroscopically [3] and, more recently, also structurally. [4] Synthetic copper‐dioxygen complexes can be formed with different stoichiometries and binding modes depending on the ligand, temperature, solvent, counterion, etc. [2] The enzymatic oxygen atom transfer reaction to exogenous phenols has been reproduced by using two types of copper‐dioxygen complexes, namely, the m-h 2 :h 2 -peroxodicopper(II) and bisAm-oxo)dicopperA species. [2] Recently, we reported a new reactivity for tyrosinase: The asymmetric oxidation of sulfides to sulfoxides, in which the enzyme behaves as an external monooxygenase, with a co-substrate to support the catalytic reaction. [5] The only precedent for the oxidation of an exogenous sulfide by a synthetic copper complex is the report by Itoh et al. on the stoichiometric sulfoxidation reaction promoted by a bisAm-oxo)dicopperA complex. [6] They found that the reaction proceeds with fast substrate binding to the copper followed by oxygen transfer, with the latter process occurring through a direct oxygen transfer mechanism. Other examples are known in which the sulfide group undergoing oxidation is part of the ligand supporting the Cu I complex. [7] Herein we report that m-h 2 :h 2 -peroxodicopper(II) complexes derived from diaminetetrabenzimidazole ligands can also support a sulfoxidation reaction with O2 and that with a suitable sacrificial co-substrate the reaction can be carried out catalytically, similarly to reactions promoted by tyrosinase. The catalytic oxidation of sulfides is a process of considerable interest because organic sulfoxides are synthetic intermediates for the preparation of biologically active molecules. [8a] However, the methods based on metal catalysis in general make use of peroxides, [8b‐e] whereas use of molecular oxygen is less frequent. [8f] In any case, the nature of the catalyst oxidizing species is often unknown. Of the catalytic processes reported, only a few that concern the oxidation of sulfides by Cu II complexes in the presence of hydrogen peroxide have appeared, [9] and the catalytic reaction occurs with high efficiency in only one case. [9c]

Isolation of Ochrobactrum sp.QZ2 from sulfide and nitrite treatment system

A bacterial strain QZ2 was isolated from sludge of anoxic sulfide-oxidizing (ASO) reactor. Based on 16S rDNA sequence analysis and morphology, the isolate was identified as Ochrobactrum sp. QZ2. The strain was facultative chemolithotroph, able of using sulfide to reduce nitrite anaerobically. It produced either elemental sulfur or sulfate as the product of sulfide oxidation, depending on the initial sulfide and nitrite concentrations. The optimum growth pH and temperature for Ochrobactrum sp. QZ2 were found as 6.5–7.0 and 30 °C, respectively. The specific growth rate (μ) was found as 0.06 h −1 with a doubling time of 19.75 h; the growth seemed more sensitive to highly alkaline pH. Ochrobactrum sp. QZ2 catalyzed sulfide oxidation to sulfate was more sensitive to sulfide compared with nitrite as indicated by IC 50 values for sulfide and nitrite utilization implying that isolate was relatively more tolerant to nitrite. The comparison of physiology of Ochrobactrum sp. QZ2 with those of other known sulfide-oxidizing bacteria suggested that the present isolate resembled to Ochrobactrum anthropi in its denitrification ability.

New chiral Schiff bases derived from (+)- and (−)-α-pinenes in the metal complex catalyzed asymmetric oxidation of sulfides

New chiral Schiff bases were derived from (+)- and (−)-α-pinenes for the first time. Coordinated to vanadium ions, they can be used as ligands in catalytic oxidation of sulfides into chiral sulfoxides. Conditions for the asymmetric oxidation of thioanisole to methyl phenyl sulfoxide in optical purity up to 32% were found. Variation of substituents in the ligand has a significant effect not only on enantioselectivity of the reaction, but also on absolute configuration of the sulfoxide formed.