Thioether Oxidation with H<sub>2</sub>O<sub>2</sub> Catalyzed by Nb‐Substituted Polyoxotungstates: Mechanistic Insights

Zalomaeva, Olga V.; Maksimchuk, Nataliya V.; Maksimov, G. M.; Kholdeeva, Oxana A.

doi:10.1002/ejic.201801108

Cited by 14 publications

(7 citation statements)

References 80 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…After 48 h of hydrogen peroxide treatment, the signal due to a sulfoxide group in the infrared spectrum at 1065 cm –1 increases. The mechanism of oxidation of sulfur to sulfones via sulfoxides is well known from previous studies. − After 120 h of treatment, all signals, besides the carbonyl, amide I, and amide II bands, showed a decrease in intensity. The reduced intensity of the SO signal at 1038 cm –1 in comparison to 48 h suggests that sulfur dioxide is eliminated in the oxidation process.…”

Section: Resultsmentioning

confidence: 69%

Oxidation-Sensitive Core–Multishell Nanocarriers for the Controlled Delivery of Hydrophobic Drugs

Rajes

Walker

Hadam

et al. 2021

ACS Biomater. Sci. Eng.

View full text Add to dashboard Cite

A synthetic route for oxidation-sensitive core− multishell (osCMS) nanocarriers was established, and their drug loading and release properties were analyzed based on their structural variations. The nanocarriers showed a drug loading of 0.3−3 wt % for the anti-inflammatory drugs rapamycin and dexamethasone and the photosensitizer meso-tetra-hydroxyphenylporphyrin (mTHPP). Oxidative processes of the nanocarriers were probed in vitro by hydrogen peroxide, and the degradation products were identified by infrared spectroscopy supported by ab initio calculations, yielding mechanistic details on the chemical changes occurring in redox-sensitive nanocarriers. Oxidationtriggered drug release of the model drug Nile Red measured and assessed by time-dependent fluorescence spectroscopy showed a release of up to 80% within 24 h. The drug delivery capacity of the new osCMS nanocarriers was tested in ex vivo human skin with and without pretreatments to induce local oxidative stress. It was found that the delivery of mTHPP was selectively enhanced in skin under oxidative stress. The number and position of the thioether groups influenced the physicochemical as well as drug delivery properties of the carriers.

show abstract

Section: Resultsmentioning

confidence: 69%

Oxidation-Sensitive Core–Multishell Nanocarriers for the Controlled Delivery of Hydrophobic Drugs

Rajes

Walker

Hadam

et al. 2021

ACS Biomater. Sci. Eng.

View full text Add to dashboard Cite

show abstract

“…% PW 4 /CNTs, which was prepared without acid, showed lower sulfoxide selectivity (84%). Therefore, catalyst acidity favors the formation of sulfoxide, most likely due to increasing electrophilicity of the oxidizing species (Zalomaeva et al, 2019). However, an unexpected trend was observed for catalyst activity.…”

Section: Catalytic Performances Of Pw 4 /Cnts Catalysts In Selective mentioning

confidence: 91%

Carbon Nanotubes Modified by Venturello Complex as Highly Efficient Catalysts for Alkene and Thioethers Oxidation With Hydrogen Peroxide

et al. 2019

Self Cite

View full text Add to dashboard Cite

In this work, we elaborated heterogeneous catalysts on the basis of the Venturello complex [PO 4 {WO(O 2 ) 2 } 4 ] 3− (PW 4 ) and nitrogen-free or nitrogen-doped carbon nanotubes (CNTs or N-CNTs) for epoxidation of alkenes and sulfoxidation of thioethers with aqueous hydrogen peroxide. Catalysts PW 4 /CNTs and PW 4 /N-CNTs (1.8 at. % N) containing 5-15 wt. % of PW 4 and differing in acidity have been prepared and characterized by elemental analysis, N 2 adsorption, IR spectroscopy, HR-TEM, and HAADF-STEM. Studies by STEM in HAADF mode revealed a quasi-molecular dispersion of PW 4 on the surface of CNTs. The addition of acid during the immobilization is not obligatory to ensure site isolation and strong binding of PW 4 on the surface of CNTs, but it allows one to increase the PW 4 loading and affects both catalytic activity and product selectivity. Catalytic performance of the supported PW 4 catalysts was evaluated in H 2 O 2 -based oxidation of two model substrates, cyclooctene and methyl phenyl sulfide, under mild conditions (25-50 • C). The best results in terms of activity and selectivity were obtained using PW 4 immobilized on N-free CNTs in acetonitrile or dimethyl carbonate as solvents. Catalysts PW 4 /CNTs can be applied for selective oxidation of a wide range of alkenes and thioethers provided a balance between activity and selectivity of the catalyst is tuned by a careful control of the amount of acid added during the immobilization of PW 4 . Selectivity, conversion, and turnover frequencies achieved in epoxidations over PW 4 /CNTs catalysts are close to those reported in the literature for homogeneous systems based on PW 4 . IR spectroscopy confirmed the retention of the Venturello structure after use in the catalytic reactions. The elaborated catalysts are stable to metal leaching, show a truly heterogeneous nature of the catalysis, can be easily recovered by filtration, regenerated by washing and evacuation, and then reused several times without loss of the catalytic performance.

show abstract

“…Polyoxometalates (POMs), a diverse family of anionic metal-oxygen species, are recognized as one of the promising catalysts for oxidation reactions. − In addition, the exposed oxygen ligands on the surface of POM are remarkably basic and thus can accept protons derived from the substrate, which significantly promotes catalytic reactions. − In recent years, the catalytic activity of POM derivatives in various organic oxidation reactions including oxidation of alkane, alcohol, benzene, aldehyde, and amine has been demonstrated by Wei and co-workers, − Neumann and co-workers, − Kholdeeva and co-workers, − Weinstock and co-workers, − and Proust et al Most notably, the organic oxidation reaction catalyzed by POM derivatives operates with oxygen (O 2 ) or hydrogen peroxide (H 2 O 2 ) as a moderate and environmentally benign oxidant.…”

Section: Introductionmentioning

confidence: 99%

Theoretical Insight into Oxidation of Anilines to Azobenzenes Catalyzed by Hexamolybdate: Outer-Sphere Electron and Proton Transfer

Wei

et al. 2023

J. Phys. Chem. C

View full text Add to dashboard Cite

Recently, the catalytic activity of Lindqvist-type hexamolybdate [Mo6O19]2– in the oxidation of an aniline derivative (LPhNH2, L = substituent) was demonstrated by Wei and co-workers (Angew. Chem. Int. Ed. 2021, 60, 6382–6385). Herein, taking phenylamine (PhNH2) oxidation to azobenzene (PhNNPh) as a model reaction, we report the density functional theory investigation of the catalytic mechanism of [Mo6O19]2– and illustrate the critical experimental phenomena. During the catalytic reaction, once the preassociation of [Mo6O19]2– and PhNH2 takes place, electron transfer and proton transfer immediately proceed to form an N radical intermediate. The higher the highest occupied molecular orbital energy of the substrate, the easier the formation of the N radical intermediate. The N–N bond formation proceeds via the second PhNH2 nucleophilic attack on the N radical intermediate. The substituent position and the N reaction site of the substrate have a significant effect on the second PhNH2 nucleophilic attack process. In the reaction process, the six MoVI of [Mo6O19]2– are still hexacoordinated, which is defined as the outer-sphere pathway. One of the factors determining the product selectivity is the electrostatic repulsion between LPhNH2 and the N radical intermediate. The experiment reveals that the product yield is increased by the addition of Na2S2O3, while the catalytic reaction is completely deactivated with Na2CO3 or K3PO4. Based on the proposed mechanism, the experimental observation was rationalized. The S2O3 2– part of Na2S2O3 has a similar function as the electron-withdrawing substituent due to its low lowest unoccupied molecular orbital (LUMO) energy, which reduces the LUMO energy of the N radical intermediate and thus facilitates PhNH2 nucleophilic attack, while the CO3 2– part of Na2CO3 or PO4 3– part of K3PO4 has an undesirable effect on the electrophilicity of the N radical intermediate, resulting in the interruption of the catalytic reaction. This work would provide a detailed understanding of the catalytic reaction.

show abstract

Thioether Oxidation with H₂O₂ Catalyzed by Nb‐Substituted Polyoxotungstates: Mechanistic Insights

Cited by 14 publications

References 80 publications

Oxidation-Sensitive Core–Multishell Nanocarriers for the Controlled Delivery of Hydrophobic Drugs

Oxidation-Sensitive Core–Multishell Nanocarriers for the Controlled Delivery of Hydrophobic Drugs

Carbon Nanotubes Modified by Venturello Complex as Highly Efficient Catalysts for Alkene and Thioethers Oxidation With Hydrogen Peroxide

Theoretical Insight into Oxidation of Anilines to Azobenzenes Catalyzed by Hexamolybdate: Outer-Sphere Electron and Proton Transfer

Contact Info

Product

Resources

About

Thioether Oxidation with H2O2 Catalyzed by Nb‐Substituted Polyoxotungstates: Mechanistic Insights

Cited by 14 publications

References 80 publications

Oxidation-Sensitive Core–Multishell Nanocarriers for the Controlled Delivery of Hydrophobic Drugs

Oxidation-Sensitive Core–Multishell Nanocarriers for the Controlled Delivery of Hydrophobic Drugs

Carbon Nanotubes Modified by Venturello Complex as Highly Efficient Catalysts for Alkene and Thioethers Oxidation With Hydrogen Peroxide

Theoretical Insight into Oxidation of Anilines to Azobenzenes Catalyzed by Hexamolybdate: Outer-Sphere Electron and Proton Transfer

Contact Info

Product

Resources

About

Thioether Oxidation with H₂O₂ Catalyzed by Nb‐Substituted Polyoxotungstates: Mechanistic Insights