Fullerene Bonding Type – Chemical Bonding and Electronic Structure of Buckyballs

There are plenty of reasons why you should know more about fullerene bonding type. Since its discovery, Buckminsterfullerene draws an attention of the whole scientific world as it has absolutely amazing chemical and physical properties which can be used in many possible applications.

It is its unique structure that holds the key to its full potential and naturally its bonding type has a lot to do with it.

Therefore in this article you will get to know more elaborate information about buckyballs’ structure and bonding in order to gain a better understanding regarding this subject.

It is a thrilling journey full of surprises and you can be a part of it.


Fullerene Bonding Type – Let’s Start with the Basics

Buckyball, Buckminsterfullerene or C₆₀ all these names stand for the same molecule. Its shape is very easy to remember as it resembles the soccer (football) ball. If you look at the actual ball there are twelve black pentagons and twenty white hexagons.

Now remove the leather, but keep the seams. What are left are sixty vertexes of carbon atoms. There are ninety covalent (also called molecular) bonds between them. To be more precise there are sixty single bonds and thirty double bonds.


C₆₀ Is an Truncated Icosahedron

In geometry it means that there are twelve regular pentagonal faces and twenty regular hexagonal faces and also sixty vertices and ninety edges.

The famous Geodesic dome is based on this structure as well. It was designed by an American architect Buckminster Fuller. And because its shape is very similar to the shape of our C₆₀, the molecule was named after it.

You should also know that buckyball is the roundest and most symmetrical molecule in the world. And this perfect symmetry is its most outstanding property. Based on these facts we can assume that buckyball is a perfect sphere.


The Actual Buckminsterfullerene Bonding Is More Complex

If you look at the model of its structure (Lewis electron dot structure), you can notice that all carbon atoms are equivalent. You can also see that each carbon is a part of two hexagons and one pentagon with two single bonds and one double bond. This is the usual carbon valence of four.

According to the valence shell electron pair repulsion (VSEPR) theory, each carbon atom has sp² hybridization.

In chemistry, the VSEPR theory is used to determine the geometry of particular molecules based on the number of electron pairs surrounding their central atoms.


What Does It Mean?

It basically means that the remaining p-orbital is available for the π- bonding with one of the neighboring carbon atoms.

In other words each carbon creates three σ bonds which have their sp² hybrid orbitals and also one π- bond that has the remaining p-orbital.

Sigma bonds (σ - bond) are the strongest types of covalent bonds. They are formed by direct overlapping between the neighboring atomic orbitals.

Pi bonds (π- bond) are also covalent chemical bonds and they are created between two adjacent atom’s unbounded p-orbitals.

So, why is the actual bonding more complex? Usually, the sp² hybrid orbitals lie in the same plane. We can take graphite as an example. It has a limitless number of planar sheets of sp² carbons which are formed into edge-sharing hexagons, where the p orbitals (p refers to the remaining 2p orbital which is responsible for the π- bond) lie parallel to each other and vertically to the graphite plane. This produces an ocean of π-electron density both below and above the plane.


The Proposed Structure of Buckminsterfullerene Is Not Planar

That is the reason why we should think about its structure in more complex way. It is a fact that all sp² hybrid orbitals are in the same plane, but if you look closely at any model of formula C₆₀, it shows pretty clearly that the environment at each carbon atom is not planar.

It means:

  • Theta (), the angle between a C-C bond vector and a p axis is 101.6°C. In planar graphite it is 90°C.
  • There is a certain strain in the molecule, because of the concavity at each sp² carbon center, but because this molecule is perfectly symmetrical, the strain is distributed evenly across the whole structure.


You might also like to know that the recent researches propose that the actual hybridization is not sp², but sp²∙³. However, the sp² hybridization is assumed as the first approach in order to create a simple, but sufficient model of the bonding and electronic structure of Buckminsterfullerene.


Other Possible Structures of Molecule C₆₀

It is very important to mention that the truncated icosahedron structure was proposed based on an unusually big peak at 720 in the mass spectrum, which was the only supporting experimental evidence. Truncated icosahedron is an elegant and attractive structure, but there were other buckyball cluster structures possible such as:

  1. Planar graphite fragments – this structure has many unsatisfied valences and it does not explain why buckyball should be any more stable than any other cluster size.
  2. Cyclic polyalkynes – this type does not have any unsatisfied valences, but the stability of C₆₀ comparing to other cluster sizes is not very easy to rationalize.
  3. Other fullerenes, for example other hollow spheres that have different atom arrangements. These fullerenes would not be as perfectly symmetrical as the truncated icosahedron and also the strain would not be distributed evenly around the whole molecule

Because of these less aesthetically-pleasing alternatives, it was essential to provide additional experimental evidence for the structure of Buckminsterfullerene.

The structure is simply fascinating and that is also the reason why it is the most researched fullerene.


Thanks to Its Structure and Bonding It Has Extraordinary Chemical and Physical Properties Such as:

  • Great stability, pressure and temperature resistance.
  • Wave-particle duality.
  • It is insoluble in water, but soluble in aromatic solvent.
  • Because it behaves like electron deficient, it reacts willingly with electron rich species.
  • Absolutely perfect symmetry
  • It can also be found in outer space.


Did You Know?

Fullerenes were discovered in 1985, but it took some time till the scientists were actually able to produce amount big enough to start proper investigations and analysis. Once it was possible the scientists all over the world got crazy about it. In that time there was high demand for fullerenes for sale although the price of it exceeded 1000 dollars per 1mg. Time has changed since then. Thanks to advanced technology and research progress, you can buy fullerenes for much more affordable prices.


The Summary

Fullerenes and their derivatives are already successfully implemented in our lives. The use of their full potential would be revolutionary.

This article described the type of the bonding of Buckminsterfullerene and introduced the possible types that could occur as well.

Now you know that the actual bonding is more complex and according to latest researches its hybridization is sp²∙³.

Do you agree with the statement that the use of their full potential would be revolutionary? Is there a bright future ahead of us or you have concerns on that matter? Please do not hesitate and share your opinion with us.

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