Spin trapping in heterogeneous electron transfer processes

Abstract

An overview of applications of spin trapping to electrochemical investigations is presented. Cited studies include characterizations of primary electrode reaction products (e.g., electrooxidations of hal.ide and pseudohalide species, electroreduction of /V-methylpyridinium ion) as well as the identification of transient intermediates arising from homogeneous reactions which are electroinitiated. The validity of spatially resolved spin trapping as a probe in the investigation of interfacial processes is demonstrated with examples drawn both from the previously reported co valent attachment of nitrone derived spin traps to silaceous surfaces and from recent studies of spin trapping in micelle and vesicle systems. Amphiphilic nitrone spin traps have been shown to coassemble with both micelles and vesicles such that the nitrone functionality resides in the interfacial region of the ordered system. The ability of these interfacially localized nitrones to trap transient radicals generated both in the hydrophobic domain of the micelle or vesicle and in the aqueous exterior domain is demonstrated. Une revue des applications des pièges à spins dans les études électrochimiques est présentée. Les travaux décrits comprennent la caractérisation des produits primaires des réactions sur les électrodes (par example, les électrooxydations des halides et des pseudohalides, et Γ électroréduction du N-méthylpyridinium) ainsi que l'identification des intermédiaires transitoires qui sont produits dans des réactions homogènes électroinitiées. La validité d'une méthode utilisant des pièges à spins situés à un endroit précis pour l'étude des procédés interfaciaux est montrée. Deux exemples sont donnés: les études déjà rapportées des pièges à spins dérivés du nitrone liés aux surfaces silacieuses, et les études récentes des pièges à spins dans les micelles et dans les vésicules. Il a été montré que les pièges à spins sont des nitrones amphiphiliques qui se sont rassemblés avec les micelles et les vésicules de sorte que le nitrone se situe dans la région interfaciale du système organisé. La capacité de ces nitrones, situés à l'inferface, de piéger les radicaux transitoires créés dans la région hydrophobique du micelle ou de la vésicule et dans la phase aqueuse extérieure est montrée.[Traduit par le journal]

Substituted α-Phenyl and α-Naphthlyl-N-tert-butyl Nitrones: Synthesis, Spin-Trapping, and Neuroprotection Evaluation

“…39,40 All of the nitrones studied have a stability domain of 3 V or more and would therefore be suitable for electrochemical spin-trapping experiments. 38,41 For PBN, the stability domain value was 3.72 V, as previously reported, 21 and for all of the functionalized nitrones, the stability domain ranges from 2.97 V for 4-HOOC−PBN−CH 2 OH to 3.82 V for NBN−CH 2 NHAc.…”

A Redox Shuttle Accelerates O2 Evolution of Photocatalysts Formed In Situ under Visible Light

“…These parameters exactly matched the simulated ESR spectrum of PBN‐Cl adducts (Figure a), which corroborated the formation of Cl· radicals under illumination. Besides, the line width of the signal was broader than that of PBN‐Cl adducts reported in the literature, because the compressed distance of radicals under heterogeneous circumstance would enhance the spin–spin interaction for broadened line width …”

The nature of chlorine-inhibition of photocatalytic degradation of dichloroacetic acid in a TiO2-based microreactor

“…6 C Cl (mM) n max (mmol g À1 There have already been reports on the detection of chlorine radicals in non-aqueous media with EPR spectrometry. [19][20][21] In our study, EPR measurements were conducted to detect the presence of chlorine radicals during the photocatalytic process by using the PBN spin-trap in chloroform solution. According to the literature, chlorine radicals react with the PBN spin-trap (I) and form a chlorinated PBN-Cl radical (II) with hyperfine splitting constants: a N E 12.7 G, a H E 0.82 G and a Cl E 5.1-6.2 G (depending on the type of Cl isotope).…”

“…According to the literature, chlorine radicals react with the PBN spin-trap (I) and form a chlorinated PBN-Cl radical (II) with hyperfine splitting constants: a N E 12.7 G, a H E 0.82 G and a Cl E 5.1-6.2 G (depending on the type of Cl isotope). 19,21 For the detection of the scavenging mechanism with chloride ions, BTACl (the source of chloride ions) and PBN were dissolved in chloroform and illuminated on the photocatalytic TiO 2 surface. The spectrum in Fig.…”