Scope and limitations of the TEMPO/EPR method for singlet oxygen detection: the misleading role of electron transfer

Nardi, Giacomo; Manet, Ilse; Monti, Sandra; Miranda, Miguel A.; Lhiaubet‐Vallet, Virginie

doi:10.1016/j.freeradbiomed.2014.08.020

Cited by 196 publications

(105 citation statements)

References 48 publications

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“…, both possibly derived from the dealkylation of trace DIPEA‐ N ‐oxide (Figure S44, Supporting Information). Upon irradiation, the same signals display a steep increase in intensity, reaching a maximum which is likely caused by the consumption of residual trace O 2 . Then, a decrease in signal intensity is detected within a few seconds, possibly due to the scavenging of the paramagnetic N1 .…”

Section: Resultsmentioning

confidence: 98%

Customizing Photoredox Properties of PXX‐based Dyes through Energy Level Rigid Shifts of Frontier Molecular Orbitals

Sciutto

Fermi

Folli

et al. 2018

Chemistry A European J

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Here we describe the synthesis of electron-rich PXX derivatives in which the energy levels of the excited states have been rigidly shifted through the insertion of imide groups. This has allowed the development of a new series of oxygen-doped photoredox-active chromophores with improved oxidizing and reducing properties. Capitalizing on the dehalogenation of organic halides as a model reaction, we could investigate the photooxidative and photoreductive potential of these molecules in model chemical transformations. Depending on the substrate, solvent and dye the reaction mechanism can follow different paths. This prompted us to consider the first chemoselective transformation protocol, in which two different C-Br bonds could be chemoselectively reacted through the sequential photoactivation of two different colorants.

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Section: Resultsmentioning

confidence: 98%

Customizing Photoredox Properties of PXX‐based Dyes through Energy Level Rigid Shifts of Frontier Molecular Orbitals

Sciutto

Fermi

Folli

et al. 2018

Chemistry A European J

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“…Thespin trap is electrochemically oxidized, which triggers ar eaction with triplet oxygen to form 4-Oxo-TEMPO. [24,31] Thepresence of these four phases shows that at ime-and voltage-resolved in operando EPR experiment is critical for unraveling the different mechanisms for the formation and decomposition of 4-Oxo-TEMPO (Figure 3).…”

Section: Angewandte Chemiementioning

confidence: 99%

Singlet Oxygen Formation during the Charging Process of an Aprotic Lithium–Oxygen Battery

et al. 2016

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Aprotic lithium-oxygen (Li-O2 ) batteries have attracted considerable attention in recent years owing to their outstanding theoretical energy density. A major challenge is their poor reversibility caused by degradation reactions, which mainly occur during battery charge and are still poorly understood. Herein, we show that singlet oxygen ((1) Δg ) is formed upon Li2 O2 oxidation at potentials above 3.5 V. Singlet oxygen was detected through a reaction with a spin trap to form a stable radical that was observed by time- and voltage-resolved in operando EPR spectroscopy in a purpose-built spectroelectrochemical cell. According to our estimate, a lower limit of approximately 0.5 % of the evolved oxygen is singlet oxygen. The occurrence of highly reactive singlet oxygen might be the long-overlooked missing link in the understanding of the electrolyte degradation and carbon corrosion reactions that occur during the charging of Li-O2 cells.

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“…The4 -Oxo-TEMPO amount starts to increase once the electrode potential exceeds about 3.55 V, which is close to the thermodynamic threshold for 1 O 2 formation (3.45-3.55 V), thus suggesting that this increase is caused by the reaction of the spin trap with 1 O 2 (Scheme 1). [24,31] Thepresence of these four phases shows that at ime-and voltage-resolved in operando EPR experiment is critical for unraveling the different mechanisms for the formation and decomposition of 4-Oxo-TEMPO ( Figure 3). [28][29][30] Above approximately 3.9 Vduring phase IV,another increase in the amount of 4-Oxo-TEMPO is accompanied by the consumption of oxygen, as seen in the OEMS data.…”

Section: Angewandte Chemiementioning

confidence: 99%

Singlet Oxygen Formation during the Charging Process of an Aprotic Lithium–Oxygen Battery

et al. 2016

View full text Add to dashboard Cite

Aprotic lithium-oxygen (Li-O 2 )b atteries have attracted considerable attention in recent years owing to their outstanding theoretical energy density.Am ajor challenge is their poor reversibility caused by degradation reactions,which mainly occur during battery charge and are still poorly understood. Herein, we showt hat singlet oxygen ( 1 D g )i s formed upon Li 2 O 2 oxidation at potentials above 3.5 V. Singlet oxygen was detected through areaction with aspin trap to form as table radical that was observed by time-and voltageresolved in operando EPR spectroscopyi nap urpose-built spectroelectrochemical cell. According to our estimate,alower limit of approximately 0.5 %o ft he evolved oxygen is singlet oxygen. The occurrence of highly reactive singlet oxygen might be the long-overlooked missing link in the understanding of the electrolyte degradation and carbon corrosion reactions that occur during the charging of Li-O 2 cells.

show abstract

Scope and limitations of the TEMPO/EPR method for singlet oxygen detection: the misleading role of electron transfer

Cited by 196 publications

References 48 publications

Customizing Photoredox Properties of PXX‐based Dyes through Energy Level Rigid Shifts of Frontier Molecular Orbitals

Customizing Photoredox Properties of PXX‐based Dyes through Energy Level Rigid Shifts of Frontier Molecular Orbitals

Singlet Oxygen Formation during the Charging Process of an Aprotic Lithium–Oxygen Battery

Singlet Oxygen Formation during the Charging Process of an Aprotic Lithium–Oxygen Battery

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