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Graphite is good conductor of electricity because one carbon atom is bonded only three carbon atoms, which enables the presence of free electrons. In fullerene 60 the carbon atoms are also bonded to three atoms so why is fullerene concidered a bad conductor of electricity?

The structure of fullerene 60

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To reiterate Ivan's comment fullerene is a bad conductor because that's what the measured properties produce as a result. The mechanism that makes it a bad conductor is that it has shorter range continuity than graphite. In graphite the carbon is made of sheets that can be as long as the sample. These sheets have fairly high conductivity, but when the electrons must jump between sheets to continue its path, this is when the conductivity value for the bulk material lowers. Extrapolate this to fullerene. If the fullerene molecule itself had high conductivity, it would still require the electrons to jump between molecules every few nanometers. This can produce a rather large resistivity for the bulk material much more so than observed in graphite.

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The sheets in graphene basically extend all through the entire material; you essentially have one macroscopic orbital going from one side of a pencil to the other. Push an electron in on one side and one will come out on the other. Great.

In fullerene, however, you have distinct little footballs that are just lying next to each other. You can easily push electrons around within one football, but it’s hard to get them moving between footballs. You would need to push them from one end of your material to the other, though; so it doesn’t help that they happily circle their football.

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    $\begingroup$ I think it's worthwhile mentioning that (ideal) graphene is a 2D conductor. And a single Bucky ball should be quite a good conductor... but that's just atomic scale thought experimentation. $\endgroup$ Dec 28, 2019 at 10:15
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The answer lies apparently in the symmetry of the molecule. Have a look at this explanation. (However, I found this question because I wanted more info, since I am not comfortable with all the symmetry arguments made there. So if any expert could have a look and agree to what is said there, id be happy.)

Also saying that the charge carriers have to jump which makes it an insulator, might also not be a good explanation. There is plenty research done in the field of organic electronics, where $\ce{C60}$ serves as electron acceptor an then also conducts current. Have a look here for example. This also does make sense considering the picture given in the above link.

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  • $\begingroup$ The symmetry argument is pretty much irrelevant. The problem is that buckminsterfullerene is a small molecule not a large flat plane where electrons are delocalised across the whole plane as is the case in graphite. Electrons have no easy mechanism to jump between the very small individual molecules but in graphite can easily move across the whole plane. $\endgroup$
    – matt_black
    Apr 29 at 18:54
  • $\begingroup$ It's not that simple. If so why is superconductivity observed on doping with alkali metals ? $\endgroup$
    – Ian Bush
    Apr 29 at 21:00
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    $\begingroup$ Well but the symmetry argument gives a closed shell. If the next state has an energy that cannot be reached with thermal energy, it is an insulator not matter if it was a small molecule or an extended sheet. At least that is how I understand that. $\endgroup$
    – Martin
    Apr 30 at 9:17

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