Does complete electron dissociation occur in fullerenes?

[RyanJ]

A question I came upon when I was reading about fullerenes today.

 

In benzene we have one non-bonded p electron in each carbon atom. Due to the overlap in the p shells the electrons are dissociated above and below the plane of the molecule in a pi delocalised system.

 

In a fullerene that for example has carbons linked in the same way, with only three bonds leaving one non-bonded electron.

 

Would the p orbitals in adjacent carbon rings over lap allowing the electrons to be dissociated over the whole molecule or are they limited to just a few ring groups?

 

Thanks!

[5614]

AFAIK the electrons are most likely to be found in the center of the fullerene, ie. within the ball structure.

 

You know the electron's position is given by a probability field, so I would have as a guess that the regions inside the fullerene and very close to the outside would be where the probability field is highest - that is, where the electrons are most likely to be found.

 

Hmm, interestingly enough if you check out the QM part of the fullerene entry on wiki:

http://en.wikipedia.org/wiki/Fullerene#Quantum_mechanics

then it says that the electrons do not delocalise over the whole Buckminsterfullerene molecule. This is to do with whether the electrons can delocalise over the whole molecule whilst remaining in a stable state. 60 electrons cannot do this. It says that in water it tends to pick up two more electrons and become an anion. It also suggests that bucky balls might try to form a metallic bond between each other.

 

Which doesn't really answer the question... maybe someone else can help us.

[RyanJ]

Actually it does provide more of an answer than you would think.

 

If this can't actually occur for larger fullerenes as it would have an adverse affect on stability, maybe it could still occur on smaller ones.

 

If the electron density is higher inside the actual molecule this also makes for some interesting discussion points, the fillerenes should be quite inert but if you could construct one with molecules inside it then it should be far more reactive and able to form different compounds. I wonder if there is a way to test this? I've heard of metals being "sealed" within the fullerene as well as other things but I wonder if the inner surface would actually be more reactive.

 

If anyone has any more information please post, fullerene's are very interesting and I'm interested in their chemical properties.

[5614]

It's not the fact that lots of electrons make it unstable, it is that having specifically 60 electrons is not stable. 50 or 98 electrons would be.

 

I've heard of a molecule being held within another molecule, that would be called host-guest chemistry, I think. I suppose if a molecule was inside a fullerene it would be trapped, but how would it get there in the first place?

 

Also I think that adding another molecule inside the fullerene would change the electron configuration. You can't have the electrons deep inside the fullerene if there's a big molecule there. And if the outside of this inner-molecule was negative, like CCl4, then the fullere's electrons would be repelled from the inside. I'm not saying they would go outside, I don't know, but it would have an effect.

[RyanJ]

Reading Wiki's entry is interesting because it suggests Buckminsterfullerene doesn't actually delocalise over the whole system but others actually may.

 

If this is the case then this would be of great interest because of the similarities it may have with benzene (and the extreme differences).

 

Your correct, my research shows that adding any molecule within the fullerene does affect its electron structure. Depending on the molecule of course. (Wasn't using a metal within the atom or replacing one of its carbons with a metallic element something they consider to be a potential super conductor?). I've heard of grouped being bonded to the outside of the molecule but not the inside, I wonder if this is some indication as too the bonding within the molecule.

 

Research suggests the bonding within the molecule may be similar too graphite, if this is so then it does explain some of its properties such as electrical conductivity. I quote:

 

Graphite can conduct electricity due to the vast electron delocalization within the carbon layers. These electrons are free to move' date=' so are able to conduct electricity. However, the electricity is only conducted within the plane of the layers.

[/quote']

 

If the bonding within the molecule is similar doesn't this mean something similar to delocalisation can occur over a whole molecule (on the larger ones anyway)?

[5614]

If the bonding within the molecule is similar doesn't this mean something similar to delocalisation can occur over a whole molecule (on the larger ones anyway)?

I'm lost, where's the quote from?

 

Graphite conducts because there are many delocalised electrons between the planes of graphite. As the quote says, as the electrons are situated between the graphite layers or planes it can only conduct along the planes, the electrons cannot easily travel through the layers of carbon atoms.

 

Whereas in a fullerene you have electrons in the middle of a sphere of carbon atoms. How is that, in any way, similar to graphite?

 

My chemistry teacher thinks that trying to get a guest-compound to go inside a fullerene (which would act as the host) would be a good PhD project. He's also interested in what the electrons would do in that situation, as well as where exactly they are in a standard C60 molecule.

[RyanJ]

I'm lost, where's the quote from?

 

From an organic textbook in school, it is discussing similar aspects of benzene, fullerenes and other carbon-type compounds including graphite and diamond.

 

Whereas in a fullerene you have electrons in the middle of a sphere of carbon atoms. How is that, in any way, similar to graphite?

 

If I understand it the book was referring to the way electrons can delocalise over the separate hexagonal segments. I'm reading another book and hopefully it will give a little more insight into how the electrons act

 

My chemistry teacher thinks that trying to get a guest-compound to go inside a fullerene (which would act as the host) would be a good PhD project. He's also interested in what the electrons would do in that situation, as well as where exactly they are in a standard C60 molecule.

 

That would be really interesting, studies have been done but a yet little in-depth work... could be interesting!

[RyanJ]

I was doing a little internet research into this and I dig up an interesting web pagehere.

 

It suggests that trapping a molecule inside such ad tritium, nitrogen, carbon monoxide etc. inside a molecule it does not make the more the fullerene more unstable as I would expect from a structure with most of its electrons delocalised inside the compound. Does this mean that maybe the electrons would be evenly disociated over the inner and outer surfaces of the structure rather than taking preference to one or the other?

 

I'm not all too sure about it but it seems to make scene that if the electrons were dissociated over the inner surface then shouldn't the repulsion of the molecule inside the structure try to push it apart or do we need to consider the energy of confinement of the molecule inside verses the energy to break the bonds allowing it to escape?

[Klor204]

Hi, I know this is an old post but it came up on google.

 

Fullerene has 5 degenerate HOMO orbitals and 3 degenerate LUMO orbitals, the de-localization isn't throughout the whole ball because of the strained shape.

 

Here is an electronic model developed computationally HOMO is Blue and Yellow, LUMO is

and LUMO is Gold and Green

 

Sources: My Dissertation was on this