The origin of the ‘spike’ in the EPR spectrum of C60−

Paul, Parimal; Bolskar, Robert D.; Clark, Alex M.; Reed, Christopher A.

doi:10.1039/b003428m

Cited by 26 publications

(28 citation statements)

References 9 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…As established earlier, 16 the central narrow signal seen with 0.8 equiv (g ) 2.0012, ∆H pp ) 2.0 G) is assigned to an S ) 1/2 (doublet) spin state of C 120 O -. The "wings" that grow in next with 2 equiv of reducing agent ( Figure 1b) are typical of overlapping signals arising from S ) 1 (triplet) spin states.…”

Section: Resultsmentioning

confidence: 74%

“…-(with its attendant narrow line "spike" due to C 120 O -) 16 gradually disappears (see Figure 3a,b). A slight excess of Co(Cp*) 2 can be added to push the reduction of C 60 2-to completion because, as judged by near-IR spectroscopy, Co-(Cp*) 2 is not a strong enough reducing agent to produce C 60 3-in the present solvent system.…”

Section: Resultsmentioning

confidence: 99%

“…We have recently shown that the long-debated origin of the extraneous "spike" in the EPR spectrum of C 60 -is due to the presence of C 120 O -. 16 This arises from C 120 O impurity in airexposed samples of C 60 . 17 It behooved us therefore to investigate whether the features ascribed to thermally accessible excited states in the EPR spectra of the C 60 2-and C 60 3-ions might also be reinterpreted in terms of C 120 O n-impurities.…”

mentioning

confidence: 99%

See 2 more Smart Citations

Artifacts in the Electron Paramagnetic Resonance Spectra of C₆₀ Fullerene Ions: Inevitable C₁₂₀O Impurity

et al. 2002

Self Cite

View full text Add to dashboard Cite

Aspects of the electron paramagnetic resonance (EPR) spectra of C60 n-fulleride ions (n ) 2, 3) and the EPR signal observed in solid C60 are reinterpreted. Insufficient levels of reduction and the unrecognized presence of C120O, a ubiquitous and unavoidable impurity in air-exposed C60, have compromised most previously reported spectra of fullerides. Central narrow line width signals ("spikes") are ascribed to C 120O n-(n ) odd). Signals arising from axial triplets (g ∼ 2.0015, D ) 26-29 G) in the spectrum of C60 2-are ascribed to C120O n-(n ) 2 or 4). Their D values are more realistic for C120O than C60. Less distinct signals from "powder" triplets (D ∼ 11 G) are ascribed to aggregates of C120O n-(n ) odd) arising from freezing nonglassing solvents. In highly purified samples of C60, we find no evidence for a broad ∼30 G signal previously assigned to a thermally accessible triplet of C60 2-. The C60 2-ion is EPRsilent. Signals previously ascribed to a quartet state of the C60 3-ion are ascribed to C120O 4-. Uncomplicated, authentic spectra of C60 -and C60 3-become available when fully reduced samples are prepared under strictly anaerobic conditions from freshly HPLC-purified C60. Solid off-the-shelf C60 has an EPR signal (g ∼ 2.0025, ∆Hpp ∼ 1.5 G) that is commonly ascribed to the radical cation C60•+ . This signal can be reproduced by exposing highly purified, EPR-silent C60 to oxygen in the dark. Doping C60 with an authentic C60•+ salt gives a signal with much greater line width (∆Hpp ) 6-8 G). It is suggested that the EPR signal in airexposed samples of C60 arises from a peroxide-bridged diradical, •C60-O-O-C60• or its decomposition products rather than from C60 •+ . Solid-state C60 is more sensitive to oxygen than previously appreciated such that contamination with C120O is almost impossible to avoid.The addition of electrons to C 60 is its most characteristic chemical property. As a consequence, over the past decade, a great deal of effort has been put into characterizing the electronic structure of fulleride anions, C 60 n-. 1 In this paper, we show that the electron paramagnetic resonance (EPR) characterization of these ions has been significantly compromised by imprecise levels of reduction and by the presence of an unrecognized impurity in [60]-fullerene, namely, C 120 O.In addition, we question the widely held belief that the EPR signal commonly observed in solid "pristine" C 60 is due to the radical cation C 60•+ . [2][3][4][5][6] In contrast to the easy addition of electrons, the removal of electrons from C 60 is extremely difficult. 7 Thus, the formation of air-stable C 60 •+ radical cation centers is not easy to chemically rationalize. Now that a synthetic route to C 60•+ has become available, 8 a purposeful doping experiment into C 60 can be performed.The C 60 3-ion is a particularly important fulleride ion to characterize well because it gives rise to superconductivity in A 3 C 60 fulleride phases (A ) alkali metal). The triply degenerate nature of the t 1u lowest unoccupied molecular or...

show abstract

Section: Resultsmentioning

confidence: 74%

Section: Resultsmentioning

confidence: 99%

mentioning

confidence: 99%

See 1 more Smart Citation

Artifacts in the Electron Paramagnetic Resonance Spectra of C₆₀ Fullerene Ions: Inevitable C₁₂₀O Impurity

et al. 2002

Self Cite

View full text Add to dashboard Cite

show abstract

“…Such ESR spectra resemble closely those reported at high temperatures for many fullerides, comprising a very narrow 'spike' ESR line with DH pp of 1-2 G, frequently superimposed on a much broader signal of C À 60 ions [1]. Recent experiments have shown that the frequently debated origin of this sharp ESR signal is related to the presence of C 120 O of an unrecognized impurity in the air-exposed samples of C 60 [13,14]. Specifically, this narrow ESR signal has been assigned to a doublet spin state (S = 1/2) of C 120 O À which also accounts for the frequent temporal reduction of the C À 60 ESR line intensity, as C 60 is more easily Fig.…”

Section: Methodsmentioning

confidence: 58%

Spin dynamics and charge transfer in C60·2ferrocene studied by electron spin resonance

Guskos

Soldatov

Żołnierkiewicz

et al. 2008

Journal of Non-Crystalline Solids

View full text Add to dashboard Cite

“…The line width is very temperature dependent and decreases with decreasing temperature [32,39]. This peak has been widely discussed [1,36,40,41] and is assumed to derive from C 120 O, which is often present in C 60 samples as an impurity. At room temperature a sharp, weak signal occurs in most of the measurements.…”

Section: Solventmentioning

confidence: 99%

Reduction

2004

Fullerenes

View full text Add to dashboard Cite

The origin of the ‘spike’ in the EPR spectrum of C60−

Abstract: The long-debated origin of the narrow line-width signal in the EPR spectrum of C 60 2 is shown to be C 120 O 2 , arising from unavoidable C 120 O impurity in air-exposed samples of C 60 .

Cited by 26 publications

References 9 publications

Artifacts in the Electron Paramagnetic Resonance Spectra of C₆₀ Fullerene Ions: Inevitable C₁₂₀O Impurity

Artifacts in the Electron Paramagnetic Resonance Spectra of C₆₀ Fullerene Ions: Inevitable C₁₂₀O Impurity

Spin dynamics and charge transfer in C60·2ferrocene studied by electron spin resonance

Reduction

Contact Info

Product

Resources

About

The origin of the ‘spike’ in the EPR spectrum of C60−

Abstract: The long-debated origin of the narrow line-width signal in the EPR spectrum of C 60 2 is shown to be C 120 O 2 , arising from unavoidable C 120 O impurity in air-exposed samples of C 60 .

Cited by 26 publications

References 9 publications

Artifacts in the Electron Paramagnetic Resonance Spectra of C60 Fullerene Ions: Inevitable C120O Impurity

Artifacts in the Electron Paramagnetic Resonance Spectra of C60 Fullerene Ions: Inevitable C120O Impurity

Spin dynamics and charge transfer in C60·2ferrocene studied by electron spin resonance

Reduction

Contact Info

Product

Resources

About

Artifacts in the Electron Paramagnetic Resonance Spectra of C₆₀ Fullerene Ions: Inevitable C₁₂₀O Impurity

Artifacts in the Electron Paramagnetic Resonance Spectra of C₆₀ Fullerene Ions: Inevitable C₁₂₀O Impurity