Structural Studies of Giant Empty and Endohedral Fullerenes.

Song Wang,Fukun Li,Xingmin Wang,Guizhi Zhang,Qing Chang,Shangfeng Yang,Sergey I Troyanov

doi:10.3389/fchem.2020.607712

Abstract

Structure elucidations of giant fullerenes composed of 100 or more carbon atoms are severely hampered by their extremely low yield, poor solubility and huge numbers of possible cage isomers. High-temperature exohedral chlorination followed by X-ray single crystal diffraction studies of the chloro derivatives offers a practical solution for structure elucidations of giant fullerenes. Various isomers of giant fullerenes have been determined by this method, specially, non-classical giant fullerenes containing heptagons generated by the skeletal transformations of carbon cages. Alternatively, giant fullerenes can be also stabilized by encapsulating metal atoms or clusters through intramolecular electron transfer from the encapsulated species to the outer fullerene cage. In this review, we present a comprehensive overview on synthesis, separation and structural elucidation of giant fullerenes. The isomer structures, chlorination patterns of a series of giant fullerenes C2n (2n = 100-108) and heptagon-containing non-classical fullerenes derived from giant fullerenes are summarized. On the other hand, giant endohedral fullerenes bearing different endohedral species are also discussed. At the end, we propose an outlook on the future development of giant fullerenes.

Highlights

Giant fullerenes are those with 100 or more carbon atoms, namely, beginning with C100
It is remarkable that the giant empty fullerenes always possess different cage isomers compared with the giant endohedral metallofullerenes
When metal ions or clusters are encapsulated in a fullerene cage, charge transfer occurring between the embedded species and the carbon cage results in the carbon cage being negatively charged

Summary

INTRODUCTION

Giant fullerenes are those with 100 or more carbon atoms, namely, beginning with C100. In situ crystal growth, and subsequent single-crystal diffraction to solve the structure of the giant fullerenes using synchrotron radiation (Troyanov and Kemnitz, 2012). This method is applicable to the individual isomers of fullerenes but sometimes to fullerene mixtures. Dozens of giant fullerenes have been identified by chlorination, and the attachment patterns of chlorine atoms usually possess unique features contributing to stabilization of the chlorinated molecule. We focus on the isomer structures of giant fullerenes, and the attachment patterns of chlorine atoms. We summarize the giant endohedral metallofullerenes that have been reported and discuss their structural features

METHODOLOGY

CONCLUSION AND PROSPECTS