Electron Spin Resonance Spin Trapping Technique: Application to the Cleavage Process of Photoinitiators

Criqui, Adrien; Lalevée, Jacques; Allonas, Xavier; Fouassier, Jean‐Pierre

doi:10.1002/macp.200800303

Cited by 85 publications

(67 citation statements)

References 52 publications

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“…Spin trapping has been extensively reviewed in the past [88][89][90][91]. An interesting overview of electron spin resonance spin trapping technique (EPR-ST) has been described by Lalevée and coworkers for detecting radicals formed during the cleavage of photoinitiators [92]. The hyperfine splitting constants for the different adducts with PBN or DMPO were measured and a new set of data has been provided.…”

Section: Spin-trapping Experiments and Their Relevance In Epr Studiesmentioning

confidence: 99%

EPR Spectroscopy as a Tool in Homogeneous Catalysis Research

et al. 2015

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In the context of homogeneous catalysis, openshell systems are often quite challenging to characterize. Nuclear magnetic resonance (NMR) spectroscopy is the most frequently applied tool to characterize organometallic compounds, but NMR spectra are usually broad, difficult to interpret and often futile for the study of paramagnetic compounds. As such, electron paramagnetic resonance (EPR) has proven itself as a useful spectroscopic technique to characterize paramagnetic complexes and reactive intermediates. EPR spectroscopy is a particularly useful tool to investigate their electronic structures, which is fundamental to understand their reactivity. This paper describes some selected examples of studies where EPR spectroscopy has been useful for the characterization of open-shell organometallic complexes. The paper concentrates in particular on systems where EPR spectroscopy has proven useful to understand catalytic reaction mechanisms involving paramagnetic organometallic catalysts. The expediency of EPR spectroscopy in the study of organometallic chemistry and homogenous catalysis is contextualized in the introductory Sect. 1. Section 2 of the review focusses on examples of C-C and C-N bond formation reactions, with an emphasis on catalytic reactions where ligand/substrate non-innocence plays an important role. Both carbon and nitrogen centered radicals have been shown to play an important role in these reactions. A few selected examples of catalytic alcohol oxidation proceeding via related N-centered ligand radicals are included in this section as well. Section 3 covers examples of the use of EPR spectroscopy to study important commercial ethylene oligomerization and polymerization processes. In Sect. 4 the use of EPR spectroscopy to understand the mechanisms of Atom Transfer Radical Polymerization is discussed. While this review focusses predominantly on the application of EPR spectroscopy in mechanistic studies of C-C and C-N bond formation reactions mediated by organometallic catalysts, a few selected examples describing the application of EPR spectroscopy in other catalytic reactions such as water splitting, photo-catalysis, photo-redox-catalysis and related reactions in which metal initiated (free) radical formation plays a role are included as well. EPR spectroscopic investigation in this area of research are dominated by EPR spectroscopic studies in isotropic solution, including spin trapping experiments. These reactions are highlighted in Sect. 5. EPR spectroscopic studies have proven useful to discern the correct oxidation states of the active catalysts and also to determine the effective concentrations of the active species. EPR is definitely a spectroscopic technique that is indispensable in understanding the reactivity of paramagnetic complexes and in conjunction with other advanced techniques such as X-ray absorption spectroscopy and pulsed laser polymerization it will continue to be a very practical tool.

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Section: Spin-trapping Experiments and Their Relevance In Epr Studiesmentioning

confidence: 99%

EPR Spectroscopy as a Tool in Homogeneous Catalysis Research

et al. 2015

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“…Furthermore, the generated species in the three‐component system PMo12/(TMS) 3 Si‐H/Iod were also studied: the results (Figure S2, Supporting Information) show that both tris(trimethylsilyl)silyl radicals and phenyl radicals were formed. Interestingly, the benzyl radical19, 20 ( a N = 14.4 G, a H = 2.5 G; Figure S2, Supporting Information) could also be generated and trapped by PBN for PMo12 alone in toluene upon the Xe–Hg‐lamp irradiation; also in agreement with a hydrogen abstraction reaction.…”

Section: Resultsmentioning

confidence: 57%

“…The new species generated from the interaction between PMo12 and (TMS) 3 Si‐H, Ph 3 GeH, or Iod were clarified using ESR spin trapping experiments on PMo12/(TMS) 3 Si‐H, PMo12/Ph 3 GeH, or PMo12/Iod upon the Xe–Hg lamp irradiation. The spectra of the PBN spin adducts are given in Figure 3 and Figure S2 in the Supporting Information ( a N = 14.6 G, a H = 5.5 G; a N = 14.2 G, a H = 5.0 G, and a N = 14.2 G, a H = 2.2 G); they correspond to those of the tris(trimethylsilyl)silyl,17 the triphenylgermyl,18 and the phenyl radicals 19. No radical was observed in the absence of PMo12 or without irradiation in agreement with the photoactivated processes (3‐4).…”

Section: Resultsmentioning

confidence: 99%

Keggin‐Type Polyoxometalate ([PMo₁₂O₄₀]³⁻) in Radical Initiating Systems: Application to Radical and Cationic Photopolymerization Reactions

Xiao

Dumur

Tehfe

et al. 2013

Macro Chemistry & Physics

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New photoinitiating systems based on a polyoxometalate (POM) are proposed: phosphomolybdic acid in combination with silane, germane, or iodonium salt can be used to generate silyl, germyl, or phenyl radicals as well as silylium cations. The photochemical mechanisms are studied by steady‐state photolysis and electron spin resonance. The phosphomolybdic acid/silane/iodonium salt system can initiate either the radical photopolymerization of acrylates or the cationic photopolymerization of epoxides. The synthesis of interpenetrated polymer networks can also be carried out. The mechanical properties of the synthesized polymers are affected by the presence of POM in the matrix, as shown by their dynamic mechanical analysis (DMA).

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“…As previously mentioned, we have synthesized the [Si‐E n ‐2959Im‐A][TsO] with α‐hydroxy alkylphenone groups, therefore, the [Si‐E n ‐2959Im‐A][TsO] will form benzoyl radicals and isopropylketyl radicals after UV irradiation …”

Section: Resultsmentioning

confidence: 99%

Initiating the Photopolymerization Behaviors of Water‐Soluble Polymerizable Polysiloxane–Polyether Block Imidazolium Ionic Liquids with Antibacterial Capability

Zhang

Jiang

Gao

et al. 2017

Macro Chemistry & Physics

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Three water‐soluble polymerizable polysiloxane–polyether block imidazolium ionic liquids containing α‐hydroxy alkylphenone groups ([Si‐En‐2959Im‐A][TsO] (n = 1, 3, 5) are designed and synthesized as novel green photoinitiators. The photochemical properties and photoinitiation mechanism of the [Si‐En‐2959Im‐A][TsO] are investigated by ultraviolet absorption spectroscopy, real‐time infrared spectroscopy and electron spin resonance. [Si‐En‐2959Im‐A][TsO] exhibit good water solubility that reaches up to 12%. [Si‐En‐2959Im‐A][TsO] not only show desirable thermal properties and low saturated vapor pressure, but also effectively initiate photopolymerization. The initial weight loss of [Si‐En‐2959Im‐A][TsO] (n = 1, 3, 5) is at 256 °C and their saturated vapor pressures are less than 3.0 Pa. The migration of the photolysis fragments of [Si‐En‐2959Im‐A][TsO] from the cured material is mitigated significantly by their polymerizability and high molecular weights. Furthermore, biological tests involving Escherichia coli and Staphylococcus aureus strains in contact with the UV‐cured films initiated by [Si‐En‐2959Im‐A][TsO] demonstrate that [Si‐En‐2959Im‐A][TsO] are effective antibacterial agents. Therefore, [Si‐En‐2959Im‐A][TsO] are promising components for the preparation of environmentally friendly materials and antibacterial coatings.

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Electron Spin Resonance Spin Trapping Technique: Application to the Cleavage Process of Photoinitiators

Cited by 85 publications

References 52 publications

EPR Spectroscopy as a Tool in Homogeneous Catalysis Research

EPR Spectroscopy as a Tool in Homogeneous Catalysis Research

Keggin‐Type Polyoxometalate ([PMo₁₂O₄₀]³⁻) in Radical Initiating Systems: Application to Radical and Cationic Photopolymerization Reactions

Initiating the Photopolymerization Behaviors of Water‐Soluble Polymerizable Polysiloxane–Polyether Block Imidazolium Ionic Liquids with Antibacterial Capability

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Electron Spin Resonance Spin Trapping Technique: Application to the Cleavage Process of Photoinitiators

Cited by 85 publications

References 52 publications

EPR Spectroscopy as a Tool in Homogeneous Catalysis Research

EPR Spectroscopy as a Tool in Homogeneous Catalysis Research

Keggin‐Type Polyoxometalate ([PMo12O40]3−) in Radical Initiating Systems: Application to Radical and Cationic Photopolymerization Reactions

Initiating the Photopolymerization Behaviors of Water‐Soluble Polymerizable Polysiloxane–Polyether Block Imidazolium Ionic Liquids with Antibacterial Capability

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Keggin‐Type Polyoxometalate ([PMo₁₂O₄₀]³⁻) in Radical Initiating Systems: Application to Radical and Cationic Photopolymerization Reactions