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Fine structure in the solution state 13C-NMR spectrum of C60 and its endofullerene derivatives

Fine structure in the solution state 13C-NMR spectrum of C60 and its endofullerene derivatives
Fine structure in the solution state 13C-NMR spectrum of C60 and its endofullerene derivatives
The 13C NMR spectrum of fullerene C60 in solution displays two small “side peaks" on the shielding side of the main 13C peak, with integrated intensities of 1.63% and 0.81% of the main peak. The two side peaks are shifted by -12.6 ppb and -20.0 ppb with respect to the main peak. The side peaks are also observed in the 13C NMR spectra of endofullerenes, but with slightly different shifts relative to the main peak. We ascribe the small additional peaks to minor isotopomers of C60 containing two adjacent 13C nuclei. The shifts of the additional peaks are due to a secondary isotope shift of the 13C resonance caused by the substitution of a 12C neighbour by 13C. Two peaks are observed since the C60 structure contains two different classes of carbon-carbon bonds with different vibrational characteristics. The 2:1 ratio of the side peak intensities is consistent with the known structure of C60. The origin and intensities of the 13C side peaks are discussed, together with an analysis of the 13C solution NMR spectrum of a 13C-enriched sample of C60, which displays a relatively broad 13C NMR peak due to a statistical distribution of 13C isotopes. The spectrum of 13C-enriched C60 is analyzed by a Monte Carlo simulation technique, using a theorem for the second moment of the NMR spectrum generated by J-coupled spin clusters.
1463-9076
11850-11860
Bacanu, George, Razvan
181f3a56-e8da-445f-b9c6-c8ead171433f
Hoffman, Gabriela
8b98ba1c-ee09-4922-82e4-a9240aa12e64
Amponsah, Michael
b044d17f-e98e-4ddf-ab5b-2ffe74fe5c85
Concistre, Maria
ec95c9d4-ecb8-4c28-a464-8c3adba9e86d
Whitby, Richard J.
45632236-ab00-4ad0-a02d-6209043e818b
Levitt, Malcolm H.
bcc5a80a-e5c5-4e0e-9a9a-249d036747c3
Bacanu, George, Razvan
181f3a56-e8da-445f-b9c6-c8ead171433f
Hoffman, Gabriela
8b98ba1c-ee09-4922-82e4-a9240aa12e64
Amponsah, Michael
b044d17f-e98e-4ddf-ab5b-2ffe74fe5c85
Concistre, Maria
ec95c9d4-ecb8-4c28-a464-8c3adba9e86d
Whitby, Richard J.
45632236-ab00-4ad0-a02d-6209043e818b
Levitt, Malcolm H.
bcc5a80a-e5c5-4e0e-9a9a-249d036747c3

Bacanu, George, Razvan, Hoffman, Gabriela, Amponsah, Michael, Concistre, Maria, Whitby, Richard J. and Levitt, Malcolm H. (2020) Fine structure in the solution state 13C-NMR spectrum of C60 and its endofullerene derivatives. Physical Chemistry Chemical Physics, 22 (21), 11850-11860. (doi:10.1039/D0CP01282C).

Record type: Article

Abstract

The 13C NMR spectrum of fullerene C60 in solution displays two small “side peaks" on the shielding side of the main 13C peak, with integrated intensities of 1.63% and 0.81% of the main peak. The two side peaks are shifted by -12.6 ppb and -20.0 ppb with respect to the main peak. The side peaks are also observed in the 13C NMR spectra of endofullerenes, but with slightly different shifts relative to the main peak. We ascribe the small additional peaks to minor isotopomers of C60 containing two adjacent 13C nuclei. The shifts of the additional peaks are due to a secondary isotope shift of the 13C resonance caused by the substitution of a 12C neighbour by 13C. Two peaks are observed since the C60 structure contains two different classes of carbon-carbon bonds with different vibrational characteristics. The 2:1 ratio of the side peak intensities is consistent with the known structure of C60. The origin and intensities of the 13C side peaks are discussed, together with an analysis of the 13C solution NMR spectrum of a 13C-enriched sample of C60, which displays a relatively broad 13C NMR peak due to a statistical distribution of 13C isotopes. The spectrum of 13C-enriched C60 is analyzed by a Monte Carlo simulation technique, using a theorem for the second moment of the NMR spectrum generated by J-coupled spin clusters.

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D0CP01282C - Accepted Manuscript
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Accepted/In Press date: 13 May 2020
e-pub ahead of print date: 13 May 2020
Additional Information: Funding Information: We thank Sally Bloodworth for experimental help. This research was supported by EPSRC (UK), grant codes EP/P009980/1, EP/P030491/1, EP/K00509X/1 and EP/T004320/1. Publisher Copyright: © the Owner Societies 2020. Copyright: Copyright 2020 Elsevier B.V., All rights reserved.

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Local EPrints ID: 440670
URI: http://eprints.soton.ac.uk/id/eprint/440670
ISSN: 1463-9076
PURE UUID: 16ed597d-df54-4992-beb7-37dc94b92be3
ORCID for Richard J. Whitby: ORCID iD orcid.org/0000-0002-9891-5502
ORCID for Malcolm H. Levitt: ORCID iD orcid.org/0000-0001-9878-1180

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Date deposited: 13 May 2020 16:34
Last modified: 15 Sep 2021 01:45

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Contributors

Author: George, Razvan Bacanu
Author: Gabriela Hoffman
Author: Michael Amponsah
Author: Maria Concistre

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