EXPERIMENTAL AND THEORETICAL DETERMINATION OF THE MAGNETIC-SUSCEPTIBILITY OF C60 AND C70

被引：167

作者：

HADDON, RC ^{[1
]}

SCHNEEMEYER, LF ^{[1
]}

WASZCZAK, JV ^{[1
]}

GLARUM, SH ^{[1
]}

TYCKO, R ^{[1
]}

DABBAGH, G ^{[1
]}

KORTAN, AR ^{[1
]}

MULLER, AJ ^{[1
]}

MUJSCE, AM ^{[1
]}

ROSSEINSKY, MJ ^{[1
]}

ZAHURAK, SM ^{[1
]}

MAKHIJA, AV ^{[1
]}

THIEL, FA ^{[1
]}

RAGHAVACHARI, K ^{[1
]}

COCKAYNE, E ^{[1
]}

ELSER, V ^{[1
]}

机构：

[1] CORNELL UNIV,DEPT PHYS,ITHACA,NY 14853

来源：

NATURE | 1991年 / 350卷 / 6313期

关键词：

D O I：

10.1038/350046a0

中图分类号：

O [数理科学和化学]; P [天文学、地球科学]; Q [生物科学]; N [自然科学总论];

学科分类号：

07 ; 0710 ; 09 ;

摘要：

THE magnetic susceptibility of C60 and the possibility of magnetic-field-induced pi-electron ring currents in this carbon spheroid have been of interest since the initial experiments on carbon clusters 1. If the molecule is regarded as a sphere with a radius of 3.5 angstrom, on which 60 electrons are free to move, the Pauling ring-current model predicts a ring-current diamagnetic susceptibility 41 times the pi-electron ring-current magnetic susceptibility of benzene with the field normal to the plane of the six-membered ring 2,3. London theory predicts, however, that the pi-electron ring currents in C60 should be weakly paramagnetic or diamagnetic, depending on the relative bond strengths used in the calculation 2,3. 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 pi-electron ring-current magnetic susceptibility. Thus C60 seems to be an aromatic molecule with a vanishingly small pi-electron ring-current magnetic susceptibility. We have performed similar measurements on C70, which indicate an appreciable pi-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.

引用

页码：46 / 47

页数：2

共 21 条

[1]

ALEMAND PM, 1991, J AM CHEM SOC, V113, P1050

[2]

Coulson C.A., 1978, HUCKEL THEORY ORGANI

[3] RING MAGNETIC-SUSCEPTIBILITIES IN CONJUGATED HYDROCARBONS [J].