Buckyball Necklace

A new type of polymer material made by stringing together the tiny football-shaped fullerene molecules has been synthesised by chemists in Spain. Under the microscope, the material resembles a string of pearls.

It’s almost fifteen years since, as deputy editor on the RSC journal Chemical Communications, I assisted in the publication of Sir Harry Kroto’s seminal paper on the discovery of buckminsterfullerene. In that time, these all-carbon molecules with their spherical, or more precisely truncated icosahedral structure have hit the science headlines many times and have even raised questions in the House of Lords.

Building blocks of a buckypearl necklace (Credit: Angewandte/Martin)

Building blocks of a buckypearl necklace (Credit: Angewandte/Martin)

Unlike their cylindrical counterparts the carbon nanotubes, fullerenes are yet to reveal their killer application. Recently, Nazario Martín and his colleagues at the University of Madrid, have developed a novel electroactive fullerene receptor molecule, a molecule that specifically recognizes and binds to the surfaces of fullerenes.

Now, the team has taken that research one step further to make hybrid molecules chimeras that bring together the fullerene receptors with fullerene themselves to form linear aggregates of molecules lined up like a string of pearls. Atomic force microscopy reveals that some strings have up to 35 buckypearls

Nazario Martin

Nazario Martin

The researchers describe the recognition of fullerenes by the receptor as involving a pincer-like grasp in which aromatic carbon rings on the pincer latch on to sections of the fullerene surface. More technically, the new buckyball receptor is a pi-extended analogue of tetrathiafulvalene (TTF),2-[9-(1, 3-dithiol-2-ylidene)anthracen-10(9H)-ylidene]-1,3-dithiole (exTTF). The complete receptor is composed of two exTTF units connected through an isophthalic diester spacer. It is the resulting large and concave aromatic surface of the exTTF units that act as the recognition motifs for the convex surface of the fullerene (C60) molecule.

This recognition process leads to a strong bond between the pincer and the pinched. Numerous analytical techniques were used to demonstrate the chemical structure of the resulting materials, including nuclear magnetic resonance spectroscopy, mass spectrometry, UV-Visible spectroscopy, and atomic force microscopy.

The researchers also point out that under certain conditions, it is possible for electrons to transfer from one complementary system to the other, which could endow the new materials with interesting electromagnetic properties for optoelectronic applications.

Further reading

Angew. Chem. Int. Edn
http://dx.doi.org/10.1002/anie.200703049

Nazario Martín Group homepage
http://www.ucm.es/info/fullerene/

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