Buckyballs or fullerenes are a class of allotrope of the element carbon infamous for the determination of their structure. They commonly compose the black, smooth soot commonly found in furnaces and fireplaces.
Even though it may seem like an article about Marvel’s Bucky Barnes, it isn’t. It is about something even more interesting from the world of chemistry. Buckyballs or fullerenes or Buckminsterfullerenes is the name given to a group of fairly recently discovered forms of elemental carbon.
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What are buckyballs or fullerenes?
It might sound difficult to believe but the fullerenes are molecules consisting of carbon atoms in pretty large numbers. Usually, they consist of 60 carbon atoms forming one molecule of the buckyball. Sometimes, however, it might also be 70, 76, 84, 90, 94, or even more carbon atoms.
They are spherical in shape so much so that together with their symmetry and sphere-like shape, they closely resemble a soccer ball. This structure is called a truncated icosahedron in technical language. It is a polygon with 60 vertices and 32 faces. 12 of these faces are pentagonal and 20 are hexagonal.
This spherical shape and the interconnections between the carbon atoms provide for a huge cage-like structure to this allotrope of carbon. This structure was initially difficult to guess. Who would have even thought that a 60 carbon molecule would turn out to resemble something as simple as a football?
You would guess the name “Buckminsterfullerene” has been given as a tribute to the scientist who discovered it but, as it happens that’s absolutely not the case.
Buckminster Fuller is the name of an architect renowned for his geodesic domes. It was these domes that gave an idea to the scientists about the structure of fullerenes. And as a tribute, this group of compounds was named after him.
Discovery of fullerenes
Fullerenes were discovered accidentally- what we call serendipity. A group of scientists was researching about certain particles found in space when they came across this group of molecules.
Fullerenes were discovered in 1985 by British chemist Harold W. Kroto of the University of Sussex and Rice University chemists Robert F. Curl and Richard E. Smalley. The team of researchers used Smalley’s experimental setup- used for things as small as a rice grain and began their experiments. They needed this since the scientists were dealing with atoms and molecules which are even smaller than a rice grain.
Carbon atoms were vaporized from graphite (another allotrope of carbon) and the technique of mass spectroscopy was used. Through this, it was concluded that the vaporized carbon atoms came together to form a 60 carbon atom molecule.
There were other clusters of a different number of carbon atoms too but they broke off making the mass spectroscopy signals vanish for them after some time.
And this is how the idea of 60 carbon atom allotrope existing came into existence!
Chemical properties of fullerenes
To figure out the structure of fullerene as a soccer ball was one big task because this allotrope of carbon was ridiculously unreactive! And it made the scientists and the researchers scratch their heads as to what makes this huge molecule so hugely inert.
Turns out, fullerenes tend to be so inert because of their closed cage-like structure. Chemically, these groups of molecules are this way because they do not have any ‘dangling bond’ or loose bonds. More simply, these are just free bonds that make a molecule react with other species.
Each carbon is connected to the other by two single bonds and one double bond- do note the number of bonds a carbon atom can form is four. Buckyballs are soluble in organic solvents like benzene. Shaking up the soot composed of fullerenes with toluene results in a red-colored solution!
Buckminsterfullerenes behave as electron-deficient species thus preferring to react with species rich in electrons, for example, the halogens or the hydroxyl group (-OH group). When they react with -OH, they are made into ‘fullerenols’.
Fullerenes tend to form two types of compounds- exohedral and endohedral. The former category comprises reacting species being present outside the cage and the latter representing the inside the cage situation.
Exohedral species are synthesized due to a chemical reaction, mostly an addition or a redox reaction, between the fullerenes and other reactive groups like the –OH group mentioned above.
Endohedral species, on the other hand, are synthesized when the transition metal complexes or metals like Lanthanum, Iridium, etc get trapped within the cage.
So even though fullerenes are themselves mostly unreactive, they have been made to, rather than synthesized
Applications of Fullerenes
Due to their recent discovery and relative inertness, there have not been many clear establishments of the applications of fullerenes. However, there are predicted applications that are being tested upon.
Buckyballs are insulators by nature but they have been observed to also possess conducting and superconducting properties at certain conditions. These properties, especially the superconducting property would lead to immense usage in the future especially in transistors and chips! (not the ones you eat)
There are also some therapeutic uses that the fullerenes can serve. Fullerenes that have metal atoms caged within them are being utilized in MRI and X Rays as contrast agents. This is because these metallofullerenes are harmless to the human body. They stay in the body for about an hour thus helping in imaging of the insides of the body.
Not just in diagnostic labs, fullerenes have also been found to possess anti-HIV properties which if exploited properly would be one of the greatest uses in medical science.
Fullerene derivatives are localized in an advantageous way thus making them suitable for the treatment of osteoporosis. Not just this, some of the derivatives have also proved themselves to have anti-microbial properties.
Even though fullerenes have been recently discovered and their structure has found us in awe, there are still a lot of applications that need to be experimented and researched upon. For how else would these allotropes with cute titles become practically effective to mankind! And not just fireplaces and furnaces even burnt food might contain fullerene in the form of soot!