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Eight simple amides have been subjected to UV irradiation in the presence of either MNP or NO. In all cases radical species were generated: these were detected by means of EPR spectroscopy in the form of different nitroxides resulting from the trapping of the primary radicals. NO acted as a double spin trap, scavenging a radical to afford a diamagnetic nitroso derivative that in turn acted as trap towards another radical unit. As amido-groups are present in components of skin tissue and may be present in many therapeutic or cosmetic products used as skin sunscreen, and NO is a ubiquitous endogenous reactive species, the nitroxides detected in the present studies might participate in radical processes triggered by sun exposure and resulting in damages, even severe, of biological tissues. (C) 2012 Elsevier Ltd. All rights reserved.

High energy radiation treatment of foodstuff for microbial control and shelf-life extension is being used in many countries. However, for consumer protection and information, the European Union has adopted the Directives 1999/2/EC and 1999/3/EC to harmonize the rules concerning the treatment and trade of irradiated foods in EU countries. Among the validated methods to detect irradiated foods the EU directives also include Electron Paramagnetic Resonance (EPR/ESR) spectroscopy. We describe herein the use of EPR for identification of four species of bivalve mollusks, i.e. brown Venus shells (Callista chione), clams (Tapes semidecussatus), mussels (Mytilus galloprovincialis) and oysters (Ostrea edulis) irradiated with 60Co γ-rays. EPR could definitely identify irradiated seashells due to the presence of long-lived free radicals, primarily CO2−, CO33−, SO2− and SO3− radical anions. The presence of other organic free radicals, believed to originate from conchiolin, a scleroprotein present in the shells, was also ascertained. The use of one of these radicals as a marker for irradiation of brown Venus shells and clams can be envisaged. We also propose a dosimetric protocol for the reconstruction of the administered dose in irradiated oysters.

Treatment of food with ionising radiations in order to increase its shelf-life is largely employed in many countries. Because of restrictions issued by different governments on the use of this technique, in addition to the identification of irradiated foodstuffs, it may be important to determine the radiation dose administered to the foodstuffs. An EPR based protocol to reconstruct the administered dose from samples of irradiated meats (rabbit, pork and duck) within an uncertainty of ±25% is reported. © 2010 Elsevier Ltd.

The antioxidant activity of five phenols, i.e. catechol, homovanillyl alcohol, homovanillic acid, gallic acid and syringic acid, present in all olive oils has been investigated. For gallic acid and syringic acid the Bond Dissociation Enthalpy BDE(O–H) has been determined through the EPR (Electron Paramagnetic Resonance spectroscopy) based on radical equilibration technique as 81.0 and 82.1 kcal mol–1, respectively. For both homovanillyl alcohol and homovanillic acid the BDE(O–H) values were assumed to be identical to that of the similar 2-methoxy-4-methylphenol (82.8 kcal mol–1). The inhibition rate constants of the above compounds and of catechol in the autoxidation of cumene (or styrene) were also determined in acetonitrile/chlorobenzene solution and corrected for hydrogen bonding by acetonitrile. The results indicate that in organic solvents gallic acid and catechol are fairly good antioxidants, while homovanillyl alcohol, homovanillic acid and syringic acid, i.e. the three 2-methoxy substituted derivatives, are much less efficient antioxidants.

The radical cation and anion of the title compound were obtained either by treatment with mercury trifluorocatetate in trifluoroacetic acid or by reduction with potassium in tetrahydrofurane. For both species the ESR spectra indicated magnetic non-equivalence of the two phosphorus atoms, as well as of the two methyl groups. Spectra attributed to the corresponding spin adducts were also observed when reacting the title compound with in situ-generated alkoxyl and thiyl radicals. MO calculations carried out for both the ionic radicals and the neutral spin adducts led to questioning the actual nature of some of the latter species.

Powdered samples of cotton, flax and viscose from textile fibres were subjected to electron beam irradiation (20–400 KGy). ESR signals were observed after irradiation. The intensity of the signals depended on the administered dose and exhibited an exponential decay with time. The ESR spectra, whose pattern depended drastically on the crystallinity of the samples, indicated the simultaneous presence of at least three carbon-centred radical species. When the whole irradiated textile fibres were quenched in a solution of glycidyl methacrylate (GMA) a significant increase of the weight was observed, the increase being strongly dependent on the administered dose and on the time interval elapsed between irradiation and quenching. Spectroscopic characterisation evidenced that GMA acted as cellulose radicals scavenger on the unsubstituted carbon of the double bond and was covalently linked to the fibre through a new C–C bond while maintaining unaltered the ester and the epoxide groups, available for further derivatisations. Because irradiation of the whole textile fibres in the range 20–200 KGy does not result in significant degradation of the material, GMA quenching of fibres irradiated in this dose range may represent an attractive route to their functionalisation.

The antimalaric drug artemisinin (QHS) is believed to operate through a mechanism initiated with the cleavage of its endoperoxidic bond induced by transition metal ions. An ESR investigation of the reaction of QHS with human serum in the presence of two spin trapping agents has led to the detection of spin adducts of carbon-centred radicals. Experiments carried out replacing the human serum with iron(II) salts led to the observation of the same spin adducts, thus supporting previous suggestions that also in vivo the drug operates via a radical-based mechanism. UV irradiation of QHS also led to the trapping of transient free radicals.

This paper is aimed at providing an overview of our studies on the title compounds as spin trapping agents, and at emphasising the links between purely cognitive, academic research and industrial applications. Phosphoryl- and thiophosphoryl-dithioformates exhibit a comparable and interesting spin trapping ability, their efficiency being analogous to that of some aromatic thioketones. The spectral hyperfine structure may provide valuable information on the nature of the trapped radical but the phosphorus hfs constant cannot be used as an useful indicator. Thionformates are less efficient spin traps than the corresponding dithioformates, being inert towards stabilised radicals such as benzyl or relatively hindered radicals as tert-butoxyl. In no case could spin adducts to thiolformates be detected, this being an indication that their carbonyl group is significantly deactivated with respect to that of organic and organometallic ketones. Because of their ability in trapping either alkyl or alkoxy radicals both kind of dithioformates were exploited as stabilisers in the processing of such polymers as polypropylene, but their outstanding performance could not compensate for some organoleptic drawbacks that were intrinsic of the thiocarbonyl function. A much more promising application of dithioesters is instead their use as RAFT chain transfer agents in the controlled polymerisation of styrene. Preliminary experiments with benzyl diethoxyphosphoryldithioformate have afforded polystyrene with a polydispersity as low as 1.17, but further studies are needed to fully elucidate the RAFT-polymerisation mechanism and to optimise its outcome.

Unusual temperature-dependent linewidth variations were observed in spin adducts of (dimenthoxy)phosphoryl methyl dithioformate with bulky free radicals, possibly involving a combination of restricted rotation of a methyl group and slow molecular tumbling. Copyright © 2002 John Wiley & Sons, Ltd.

Benzyl (diethoxyphosphoryl)dithioformate (1) and benzyl (diethoxythiophosphoryl)dithioformate (2) were studied as RAFT agents in the polymerization of styrene. The reactive intermediates involved in the process were identified by electron spin resonance spectroscopy as the species deriving from the addition of the polymer propagating radical to the chain transfer agent, in agreement with the RAFT mechanism. Both thermally and AIBN-initiated RAFT styrene polymerizations were performed at different temperatures. In general, the molar mass increased with time as expected for a controlled polymerization process. The molar mass distribution also progressively increased. Inefficient control of the molar mass distribution appears to be related to the rate of radical formation, which is not sufficiently fast compared to the overall monomer conversion, as well as to the rate of bond dissociation and reformation with respect to the propagation rate. As a result, both 1 and 2 behave as RAFT agents but, at relatively high conversion, afford polymers endowed with polydispersities as large as in conventional radical polymerizations.

Differently aged needles from a Pinus nigra Arnold tree growing in a typical urban area have been examined by means of electron paramagnetic resonance (EPR) spectroscopy, and the variation of the observed six-line Mn (II) signal was monitored for 1 year. An inverse trend has been established between the photosynthetic efficiency of the plant and the measured content of Mn (II). The possibility of using EPR spectroscopy in studying ageing and in assessing stress situations in plants is considered.

Five new phosphoryldithioformates bearing different substituents on the phosphoryl group have been synthesised and exploited as spin trapping agents in ESR experiments. While the dilauroxy substituted compound led to the observation of ESR spectra indicating photolability of either the compound as such or of its radical adducts, the three diaryloxy-phosphoryl dithioformates exhibited an excellent spin trapping ability, thus proving an attractive alternative to previously described members of this family. This was also the case for the di(2-menthoxy)phosphoryl derivative which led in all cases to very persistent radical adducts. The low melt-flow index values measured in the extrusion of polypropylene with variable additions of some of the dithioformates investigated in this and in previous studies indicated that the tested compounds have a remarkable ability to act as process stabilisers.

The addition of silyl and germyl radicals to a series of substituted cyclopentenones and cyclohexenones has been investigated using EPR spectroscopy. At low temperatures the 3-position is the preferred site for addition unless it is substituted or sterically hindered in which case addition occurs at the carbonyl oxygen. The latter process is also favoured at higher temperatures but no evidence has been obtained for either addition at the 2-position or for an intramolecular migration following initial attack at the 3- or 2-position.

The synthesis and characterisation of a new phosphorylated nitrone belonging to the spiro[indoline-naphthoxazinic] family are described. The results of spin trapping experiments which indicate the ability of this photochromic nitrone to react with carbon-, oxygen- and sulfur-centred radicals are also reported.

Electron paramagnetic resonance has been used to characterise free radicals formed by the reaction of photochemically generated tert-butoxyl radicals with a range of methyl substituted cyclopentenones and cyclohexenones. The spectra have been interpreted using computer analysis and simulation and assigned to cyclic allylic and alkyl radicals formed by abstraction of a hydrogen atom. The 1-oxocyclohept-2-en-4-yl radical derived by abstraction of bromine from 4-bromocyclohept-2-enone exhibits a temperature dependent EPR spectrum attributed to ring inversion.

Radical allylations with 2-functionalized allyl phenyl sulfones have been performed by using tris(trimethylsilyl)silane as radical mediator. Yields varied from moderate to good depending on the nature of the starting materials. EPR studies on the alkyl radical adducts of allyl sulfones have been performed and conformational information has been obtained for the tert-butyl and tetrahydrofuranyl adducts of 2-carboxy allyl tris(trimethylsilyl)silane.

Glucosyl radicals from the photoreaction of α-bromo-2,3,4,6-tetra- O -acetylglucose ( ABG ) with hexabutylditin react with phenols. 4-H 3 COC 6 H 4 O• was identified by means of EPR spectroscopy in the case of 4-methoxyphenol, and the corresponding α - O -glucoside was isolated along with 1- and 2-deoxysugars and the dimers of glucosyl radical. The present results are consistent with the formation of α - O -glucosides observed in the electrochemical reaction of ABG and phenols, although in this case the dimers represent the main reaction products.

The addition of a variety of radicals to triphenylmethyl l, allyl 2, benzyl 3 and but-3-enyl (diethoxyphosphoryl)dithioformate 4 has been investigated by EPR spectroscopy. Reactions with the first substrate always led to displacement of the triphenylmethyl radical; release of the allylic or benzylic moieties from 2 and 3 was observed above 243 K under photolytic conditions, while at lower temperatures or in the dark the adducts resulting from thiophilic addition of the radicals were detected. The weak EPR spectra detected when reacting dithioformates 1–4 and methyl(diethoxyphosphono)dithioformate 5 with Grignard reagents are attributed to the radical anions of the starting compounds and to their ion pairs with magnesium cations.

Contrary to the symmetrically substituted 1,8-dibenzoylnaphthalenes the corresponding 1,8-diacylnaphthalenes were found to exist solely in the anti (racemic) conformation. The structure was assessed by 13 C (magic angle spinning) NMR spectroscopy as well as by X-ray diffraction in the solid and by differential NOE experiments in solution. The presence of prochiral substituents allowed to measure the degenerate enantiomerisation barrier by computer simulation of the 1 H NMR line shape as fuction of temperature. The barriers increased with the bulkiness of the alkyl substituents R bonded to the carbonyl moiety: they cover the range 6.7 kcal mol -1 (R=CH 2 Me) to 9.0 kcal mol -1 (R=CH 2 Ph)

New physical evidence to support a ketyl radical-anion mechanism for the [3,3]-sigmatropic rearrangement is presented. With use of EPR spectroscopy, spectra are observed that can be attributed to 8, an acyl radical-anion species resulting from a [3,3]-rearrangement; this also functions as a key intermediate in the process. The spectrum of an additional paramagnetic species resulting from further addition of tin-centered radicals to the reaction product was also observed.

The analysis of the NOE effects based upon the interproton distances obtained by MM2 calculations yields a quantitative assessment of the conformer population of 1- and 2-naphthaldehydes (Z-conformer 85% and 12% respectively).

Radical allylations with 2-functionalized allyl phenyl sulfones have been performed by using tris(trimethylsilyl)silane as radical mediator. Yields varied from moderate to good depending on the nature of the starting materials. EPR studies on the alkyl radical adducts of allyl sulfones have been performed and conformational information has been obtained for the tert-butyl and tetrahydrofuranyl adducts of 2-carboxy allyl tris(trimethylsilyl)silane.

The radical anions from thiobenzophenone, thiobenzoyltriphenylsilane, and 3,5-di-tert-butylthiobenzoyltriphenylsilane were detected by EPR spectroscopy when these compounds were reacted with a number of Grignard reagents, RMgBr. The radical adducts resulting from addition of R• radicals to the thiones were also detected. The formation of the radical anions indicates unambiguously the occurrence of a SET process which might be the initial stage of these reactions. In the case of tris(trimethylsilyl)ethanethial only the radical adducts were detected. The first reduction potentials of these thiones have also been measured in order to verify the feasibility of the SET process. In agreement with the EPR experiments, the calculated standard free energy changes suggest that electron transfer is possible in the first three cases and disfavored with the thioaldehyde.

The reactions of six differently substituted photochromic spiro[indoline-naphtopyrans] with ‡NO or ‡NO2 under normal daylight conditions have been investigated by means of EPR spectroscopy along with those of three structurally related spiro[indoline-benzopyrans]. The spectra due to cyclic oxynitroxides originating from double trapping of biradicals by ‡NO were observed with the three latter derivatives, this finding being in agreement with previous results. Similar signals were also observed with the six former compounds, but in this case they were responsible for just a minor component of the spectra, the main spectral signals being due to hitherto unreported paramagnetic species that on the basis of their spectral parameters are identified as iminoxy radicals. DFT calculations at the B3LYP/6-31G* level carried out on a variety of radicals support this assignment.

The reactions of six differently substituted photochromic spiro[indoline-naphtopyrans] with ·NO or ·NO2 under normal daylight conditions have been investigated by means of EPR spectroscopy along with those of three structurally related spiro[indoline-benzopyrans]. The spectra due to cyclic oxynitroxides originating from double trapping of biradicals by ·NO were observed with the three latter derivatives, this finding being in agreement with previous results. Similar signals were also observed with the six former compounds, but in this case they were responsible for just a minor component of the spectra, the main spectral signals being due to hitherto unreported paramagnetic species that on the basis of their spectral parameters are identified as iminoxy radicals. DFT calculations at the B3LYP/6-31G* level carried out on a variety of radicals support this assignment. Copyright © 2009 John Wiley & Sons, Ltd.

The redox properties of ethyl diethoxyphosphoryldithioacetate (1), methyl diethoxyphosphorylfluorodithioacetate (2) and methyl diethoxyphosphoryldifluorodithioacetate (3) were measured by cyclic voltammetry. Addition of free radicals to the three dithioesters led to the detection of the ESR spectra of the spin adducts only with the last two compounds. Based on the reduction potentials of the three dithioacetates, this may be explained by capto-dative stabilization of the adducts. On the basis of DFT calculations, the temperature dependent variations of the spectral patterns exhibited by the radicals were attributed to restricted rotation about the Calpha-SMe bond.

The electrochemical reduction on silver of peracetylated 6-iodo-6-deoxy-beta-maltose (2), 6-iodo-6-deoxy-beta-maltotriose (3) and 6'-iodo-6'-deoxy-beta-maltose (4) has been investigated by cyclic voltammetry and performed on a preparative scale, according to the stoichiometry, -CH(2)I(2-4) + e(-) --> -CH(2)(*) + I(-). In agreement with the preparative electrolysis results, cyclic voltammetry showed different profiles for the reducing terminal-iodinated 2 and 3 and for the non-reducing terminal-iodinated 4. Compounds 2 and 3 partly dimerised to maltotetraoses mimics 7 (6,6-dimer) and 8 (5',5'-dimer) in 38% overall yield and to maltohexaose mimics 12 (6,6-dimer) and 13 (5',5'-dimer) in 30% overall yield, respectively. Compounds 7 and 12 came from the dimerisation of -CH(2)(*), primary radicals at C-6, which could also abstract H-5', becoming CH(3) and generating the C-5' quaternary radicals that dimerised in 8 and 13, respectively. These products were accompanied by the maltose derivatives 9, 10 and 11 a/b in 42% overall yield and by the maltotriose derivatives 14, 15 and 16 in 48% overall yield, respectively. Compounds 9, 14 and 10, 15 came from -CH(2)(*) disproportionation to CH(3) and CH(2)=C, respectively (exocyclic double bond C-6/C-5). Compounds 11 a/b and 16 came from C-5' radical reduction, followed by acetate anion elimination (double bonds C-6'/C-5' and C-5'/C-4'). In turn, 4 afforded only the 6',6'-dimer maltotetraose mimic 17 in 60% yield, accompanied by the reduced maltose 18 in 20% yield, in which the starting CH(2)I became CH(3). Compounds 7, 8, 12, 13 and 17 belong to a class of mixed O/C malto-mimic oligosaccharides wherein an unnatural C-C bond between two saccharide units increases metabolic stability compared to their O-analogues and modulates the sugar chain conformational flexibility, a fundamental parameter in determining protein-carbohydrate binding. Direct and spin-trapping EPR studies substantiated the radical-based nature of the dimerisation processes and allowed the identification of some of the paramagnetic species involved.

The analysis of the NOE effects based upon the interproton distances obtained by MM2 calculations yields a quantitative assessment of the conformer population of 1- and 2-naphthaldehydes (Z-conformer 85% and 12% respectively).

NOE measurements, combined with MM-2 calculations, predict that the proportion of the Z conformer in the title compound is high enough (14% at room temperature) as to give line broadening effects due to E,Z exchange. Line shape analysis of the dynamic C-13 NMR signals at variable temperature yielded a free energy of activation of 8.3 Kcal/mol. One of the lines of the spectrum of the Z conformer was also directly observed (0.8% at −140°C, corresponding to 11% at room temperature if the entropy difference is assumed zero). ESR spectra and INDO calculations show that also the σ-radical (obtained by H-abstraction from the HCO moiety of the title compound) essentially adopts the E conformation.

ESR studies carried out during the reaction of ferrocenoylsilanes with Grignard reagents at low temperature led to the detection of the radical anions of the former compounds. Cyclic voltammetric experiments indicate that the observed radical anions are likely to originate through an inner-sphere electron transfer process. Different radical species were observed upon annealing, originating from destruction of the ferrocenyl moiety. Paramagnetic species were also detected on reacting ferrocenoylsilanes with LiAlH4. Copyright © 2004 John Wiley & Sons, Ltd.

The 3,3''',3'''''-tris(butylsulfanyl)- 2,2':5',2'':5'',2''',5''',2'''':5'''',2'''''-sexithiophene 1 was investigated through spectroscopic (NMR, EPR, UV/Vis-NIR), electrochemical, spectroelectrochemical and theoretical (DFT) studies. The charged species obtained upon its oxidation and reduction were characterised, showing that 1 can exist in at least five different oxidation states, that is, a neutral species, a radical cation, a dication, a radical anion, and a dianion. The long term stability of the radical cation 1+. was evidenced by the 1H NMR study in the presence of small quantities of trifluoroacetic acid (TFA). This approach allowed a comparison of the relative broadening of proton signals of 1, induced by the electron exchange process with traces of radical cation 1+., and the hfc (hyperfine coupling) constants obtained from the EPR study and DFT calculations. In the radical cation, all of the heterocyclic sulphur atoms are not significantly involved in the delocalisation of the unpaired electron, whereas the opposite holds for the radical anion. Time-dependent DFT calculations reproduced well the wavelengths of the optical transitions observed in the spectroelectrochemical experiments for all the five oxidation states and support the formation of the dianion 1(2-).

5H-Pyridophenoxazin-5-one (PPH), a new anticancer iminoquinone, is able to inhibit a large number of lymphoblastoid and solid-tumor derived cells at submicromolar concentrations. Molecular modeling calculations indicated that this compound might intercalate into DNA double strand. This was also supported by nuclear magnetic resonance studies. Since free radicals arising from anticancer quinonic drugs have been proposed to be key species responsible for the DNA cleavage, we have endeavored in a study aimed to intercept and identify free radicals from PPH generated in bioreductive conditions. The first and second mono-electronic reduction potential of PPH were measured by means of cyclic voltammetry: the reduction potential of PPH is compatible with its reduction by such compounds as NADH, and suggested that reduction of PPH may play a role in its cytotoxicity. The radical anion PPH·- was detected by means of electron paramagnetic resonance spectroscopy and its identification was supported by DFT calculations. EPR experiments in the presence of the spin traps 5,5-dimethylpyrroline N-oxide and 5-(diethoxyphosphoryl)-5-methyl-pyrroline N-oxide suggested the occurrence of an electron transfer between the radical anion of the drug and oxygen resulting in the formation of the superoxide anion (O2·-). The enthalpy of the reaction of PPH·- with O2 was determined both in the gas phase and in solution at the B3LYP/6-31+G* level using the isodensity PCM method, and the overall process in dimethylsulfoxide was predicted as slightly exothermic. We propose that the mono-electronic reduction of PPH in close proximity to DNA may eventually lead to radicals that could cause considerable damage to DNA, thus accounting for the high cytotoxic activity of the drug. Indeed a comet assay (alkaline single cell electrophoresis) showed that PPH causes free radical induced DNA damage.

Benzyl (diethoxyphosphoryl)dithioformate (1) has been used to control the AIBN initiated radical polymerization of Styrene. In a comparative study with the more popular RAFT transfer agent benzyl dithiobenzoate (2), compound 1 led to higher molecular weight polymers, although with a slightly worse polydispersity. During the polymerization process mediated by 1 a few radicals have been intercepted and characterized by means of ESR spectroscopy. The nature and relative amount of the various radical species varied as the polymerization proceeded, matching expectations based on the generally accepted RAFT mechanism. The present ESR results induce to a reassessment of the identity of a radical species observed in a previous preliminary study.

Indolinonic and quinolinic aromatic nitroxides have been shown to efficiently inhibit free radical mediated oxidation reactions in biological systems. Since all antioxidants also possess pro-oxidant activity, possibly through a hydrogen abstraction process from suitable substrates, the relative hydrogen abstraction abilities of these compounds were evaluated also in relation to their structure. Therefore, different hydrogen donors were reacted with indolinic, indolinonic and quinolinic nitroxides and the rates of hydrogen abstraction were determined using UV-Vis spectroscopy. From the data obtained, a structure-activity relationship was found for indolinonic and indolinic nitroxides. In addition, hydrogen abstraction abilities of these compounds were much greater when compared to that of the aliphatic nitroxide TEMPO, although the antioxidant activities of these two classes of compounds are very similar.

The identification of the species observed by EPR spectroscopy in the SmI(2)-promoted coupling of N-(N', N'-dialkylaminoalkyl)benzotriazoles as substituted benzyl radicals is disputed on the basis of results obtained studying the model radical derived from tribenzylamine.

The reduction of a number of phosphoryl- and thiophosphoryl formates, monothioformates and dithioformates has been studied by means of cyclic voltammetry and EPR spectroscopy. The reduction potentials of all dithioformates are close to −1 V vs. SCE, and increase for S-alkyl monothioformates and even more for O-alkyl monothioformates. The radical anions of the compounds bearing the thiocarbonyl function have been characterised by means of EPR spectroscopy, whereas those of the compounds having the carbonyl function underwent decomposition before detection. Reduction at higher potentials led in most cases to the detection of paramagnetic dianions derived from fragmentation of the initially formed radical anions.

An α-terthiophene/cellulose triacetate film system exposed to γ-rays and electron beam shows two new bands in the visible region of the spectrum. The absorbance at 490 nm is almost stable for a long time and responds linearly to the dose applied up to 400 kGy. A second band developed at 700 nm depends on dose rate and may indicate a chain-growth. The main species responsible for the color change and EPR signal is likely to be an enlarged oligomer radical cation stabilized by a semiquinoid structure.

Irradiation of a number of different sutures largely employed in the clinical practice with either high energy electrons or with g-rays followed by quenching with glycidyl methacrylate (GMA) conveniently led to derivatization through a radical-based process. The radicals involved were detected by means of ESR spectroscopy and were characterized on the basis of their ESR spectral parameters which were also found to be consistent with the hfs constants predicted by DFT calculations. Evidence of the GMA derivatization of the sutures was obtained via (13)C CP-MAS NMR spectroscopy, while its extent was evaluated gravimetrically.

The paramagnetic species detected by EPR spectroscopy upon electrochemical reduction of bis(2,4,7-tri-tert-butyl-phenyl)-1,3-diphosphaallene in THF solution has been unambiguously identified as the title radical, the identi-fication being supported by DFT calculations