New research has revealed that the substance believed to be C₆₀F₁₆ has a double-caged structure and is actually (C₆₀F₁₆)(C₆₀).¹ 

Sergey Troyanov at Moscow State University, Russia and colleagues used x-ray diffraction to uncover the true structure of the fluorinated fullerene. 

The previously overlooked and unexpected possibility of the association of fullerene molecules during fluorination may lead to a new direction of research into the properties of fluorinated fullerene oligomers and polymers, said Troyanov. 

The double-caged fluorofullerene contains two C-60 cages, bridged by a four-membered carbon ring. Fluorine atoms are shown in green.

Isolation of what was believed to be C₆₀F₁₆ was first reported in 2000 when it was thought to have a similar structure to C₆₀F₁₈ in which all the fluorines are concentrated at one end of the fullerene molecule.² However, there has been some doubt over this structure. 'The late Professor Roger Taylor made a brilliant guess.regarding the possible dimeric nature of this compound,' said Troyanov, explaining the team's motivation. 

Halogenated fullerenes, added Troyanov, have a strong, unutilised potential as electron acceptors. The main challenges are to increase the number of compounds known and to rationalise their formation and rearrangements. This, he anticipates, will ultimately lead to their incorporation in novel functional materials.  

Caroline Moore