Experimental and theoretical determination of the magnetic susceptibility of C60 and C70

R. C. Haddon, Lynn Schneemeyer, J. V. Waszczak, S. H. Glarum, R. Tycko, G. Dabbagh, A. R. Kortan, A. J. Muller, A. M. Mujsce, M. J. Rosseinsky, S. M. Zahurak, A. V. Makhija, F. A. Thiel, K. Raghavachari, E. Cockayne, V. Elser

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Abstract

THE magnetic susceptibility of C60 and the possibility of magnetic-field-induced π-electron ring currents in this carbon spheroid have been of interest since the initial experiments on carbon clusters1. If the molecule is regarded as a sphere with a radius of 3.5 Å, on which 60 electrons are free to move, the Pauling ring-current model predicts a ring-current diamagnetic susceptibility 41 times the π-electron ring-current magnetic susceptibility of benzene with the field normal to the plane of the six-membered ring2,3. London theory predicts, however, that the π-electron ring currents in C60 should be weakly paramagnetic or diamagnetic, depending on the relative bond strengths used in the calculation2,3. With the availability of macroscopic quantities of C60 (ref. 4), it is now possible to study experimentally the magnetic properties of the molecule. Here we report on such measurements. We find that the diamagnetism of C60 is small, a result that we attribute to excited-state paramagnetic contributions to the π-electron ring-current magnetic susceptibility. Thus C60 seems to be an aromatic molecule with a vanishingly small π-electron ring-current magnetic susceptibility. We have performed similar measurements on C70, which indicate an appreciable π-electron diamagnetism, consistent with theoretical calculations. We attribute the differences in magnetic properties of these two molecules to their different fractions of five-membered ring structures. The fullerenes may thus constitute a class of compounds of 'ambiguous' aromatic character, traditional measures of which will not provide an adequate classification.

Original languageEnglish
Pages (from-to)46-47
Number of pages2
JournalNature
Volume350
Issue number6313
DOIs
StatePublished - 1 Jan 1991

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ring currents
magnetic permeability
diamagnetism
electrons
molecules
magnetic properties
carbon
ring structures
spheroids
free electrons
fullerenes
availability
benzene
radii
magnetic fields
excitation

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Haddon, R. C., Schneemeyer, L., Waszczak, J. V., Glarum, S. H., Tycko, R., Dabbagh, G., ... Elser, V. (1991). Experimental and theoretical determination of the magnetic susceptibility of C60 and C70 Nature, 350(6313), 46-47. https://doi.org/10.1038/350046a0
Haddon, R. C. ; Schneemeyer, Lynn ; Waszczak, J. V. ; Glarum, S. H. ; Tycko, R. ; Dabbagh, G. ; Kortan, A. R. ; Muller, A. J. ; Mujsce, A. M. ; Rosseinsky, M. J. ; Zahurak, S. M. ; Makhija, A. V. ; Thiel, F. A. ; Raghavachari, K. ; Cockayne, E. ; Elser, V. / Experimental and theoretical determination of the magnetic susceptibility of C60 and C70 In: Nature. 1991 ; Vol. 350, No. 6313. pp. 46-47.
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title = "Experimental and theoretical determination of the magnetic susceptibility of C60 and C70",
abstract = "THE magnetic susceptibility of C60 and the possibility of magnetic-field-induced π-electron ring currents in this carbon spheroid have been of interest since the initial experiments on carbon clusters1. If the molecule is regarded as a sphere with a radius of 3.5 {\AA}, on which 60 electrons are free to move, the Pauling ring-current model predicts a ring-current diamagnetic susceptibility 41 times the π-electron ring-current magnetic susceptibility of benzene with the field normal to the plane of the six-membered ring2,3. London theory predicts, however, that the π-electron ring currents in C60 should be weakly paramagnetic or diamagnetic, depending on the relative bond strengths used in the calculation2,3. With the availability of macroscopic quantities of C60 (ref. 4), it is now possible to study experimentally the magnetic properties of the molecule. Here we report on such measurements. We find that the diamagnetism of C60 is small, a result that we attribute to excited-state paramagnetic contributions to the π-electron ring-current magnetic susceptibility. Thus C60 seems to be an aromatic molecule with a vanishingly small π-electron ring-current magnetic susceptibility. We have performed similar measurements on C70, which indicate an appreciable π-electron diamagnetism, consistent with theoretical calculations. We attribute the differences in magnetic properties of these two molecules to their different fractions of five-membered ring structures. The fullerenes may thus constitute a class of compounds of 'ambiguous' aromatic character, traditional measures of which will not provide an adequate classification.",
author = "Haddon, {R. C.} and Lynn Schneemeyer and Waszczak, {J. V.} and Glarum, {S. H.} and R. Tycko and G. Dabbagh and Kortan, {A. R.} and Muller, {A. J.} and Mujsce, {A. M.} and Rosseinsky, {M. J.} and Zahurak, {S. M.} and Makhija, {A. V.} and Thiel, {F. A.} and K. Raghavachari and E. Cockayne and V. Elser",
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Haddon, RC, Schneemeyer, L, Waszczak, JV, Glarum, SH, Tycko, R, Dabbagh, G, Kortan, AR, Muller, AJ, Mujsce, AM, Rosseinsky, MJ, Zahurak, SM, Makhija, AV, Thiel, FA, Raghavachari, K, Cockayne, E & Elser, V 1991, 'Experimental and theoretical determination of the magnetic susceptibility of C60 and C70 ', Nature, vol. 350, no. 6313, pp. 46-47. https://doi.org/10.1038/350046a0

Experimental and theoretical determination of the magnetic susceptibility of C60 and C70 . / Haddon, R. C.; Schneemeyer, Lynn; Waszczak, J. V.; Glarum, S. H.; Tycko, R.; Dabbagh, G.; Kortan, A. R.; Muller, A. J.; Mujsce, A. M.; Rosseinsky, M. J.; Zahurak, S. M.; Makhija, A. V.; Thiel, F. A.; Raghavachari, K.; Cockayne, E.; Elser, V.

In: Nature, Vol. 350, No. 6313, 01.01.1991, p. 46-47.

Research output: Contribution to journalArticleResearchpeer-review

TY - JOUR

T1 - Experimental and theoretical determination of the magnetic susceptibility of C60 and C70

AU - Haddon, R. C.

AU - Schneemeyer, Lynn

AU - Waszczak, J. V.

AU - Glarum, S. H.

AU - Tycko, R.

AU - Dabbagh, G.

AU - Kortan, A. R.

AU - Muller, A. J.

AU - Mujsce, A. M.

AU - Rosseinsky, M. J.

AU - Zahurak, S. M.

AU - Makhija, A. V.

AU - Thiel, F. A.

AU - Raghavachari, K.

AU - Cockayne, E.

AU - Elser, V.

PY - 1991/1/1

Y1 - 1991/1/1

N2 - THE magnetic susceptibility of C60 and the possibility of magnetic-field-induced π-electron ring currents in this carbon spheroid have been of interest since the initial experiments on carbon clusters1. If the molecule is regarded as a sphere with a radius of 3.5 Å, on which 60 electrons are free to move, the Pauling ring-current model predicts a ring-current diamagnetic susceptibility 41 times the π-electron ring-current magnetic susceptibility of benzene with the field normal to the plane of the six-membered ring2,3. London theory predicts, however, that the π-electron ring currents in C60 should be weakly paramagnetic or diamagnetic, depending on the relative bond strengths used in the calculation2,3. With the availability of macroscopic quantities of C60 (ref. 4), it is now possible to study experimentally the magnetic properties of the molecule. Here we report on such measurements. We find that the diamagnetism of C60 is small, a result that we attribute to excited-state paramagnetic contributions to the π-electron ring-current magnetic susceptibility. Thus C60 seems to be an aromatic molecule with a vanishingly small π-electron ring-current magnetic susceptibility. We have performed similar measurements on C70, which indicate an appreciable π-electron diamagnetism, consistent with theoretical calculations. We attribute the differences in magnetic properties of these two molecules to their different fractions of five-membered ring structures. The fullerenes may thus constitute a class of compounds of 'ambiguous' aromatic character, traditional measures of which will not provide an adequate classification.

AB - THE magnetic susceptibility of C60 and the possibility of magnetic-field-induced π-electron ring currents in this carbon spheroid have been of interest since the initial experiments on carbon clusters1. If the molecule is regarded as a sphere with a radius of 3.5 Å, on which 60 electrons are free to move, the Pauling ring-current model predicts a ring-current diamagnetic susceptibility 41 times the π-electron ring-current magnetic susceptibility of benzene with the field normal to the plane of the six-membered ring2,3. London theory predicts, however, that the π-electron ring currents in C60 should be weakly paramagnetic or diamagnetic, depending on the relative bond strengths used in the calculation2,3. With the availability of macroscopic quantities of C60 (ref. 4), it is now possible to study experimentally the magnetic properties of the molecule. Here we report on such measurements. We find that the diamagnetism of C60 is small, a result that we attribute to excited-state paramagnetic contributions to the π-electron ring-current magnetic susceptibility. Thus C60 seems to be an aromatic molecule with a vanishingly small π-electron ring-current magnetic susceptibility. We have performed similar measurements on C70, which indicate an appreciable π-electron diamagnetism, consistent with theoretical calculations. We attribute the differences in magnetic properties of these two molecules to their different fractions of five-membered ring structures. The fullerenes may thus constitute a class of compounds of 'ambiguous' aromatic character, traditional measures of which will not provide an adequate classification.

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