accepting ability with great practical potential.
Researchers at Kyoto University
in Japan have gained new insights into the unique chemical properties
of spherical molecules composed entirely of carbon atoms, called
fullerenes.
Buckminsterfullerene (or simply ‘buckyball’) is a
molecule in which 60 carbon atoms are bonded to form a spherical shape.
It was named after structural similarities to the geodesic domes
designed by the celebrated architect Buckminster Fuller, and its unique
structure has continuously attracted the interest of scientists.
*The
buckminsterfullerene and related spherical carbon clusters with
different numbers of carbon atoms are colloquially known as fullerenes,
after Fuller’s surname.
*One of their most intriguing characteristics is a
capability to accept electrons, a process known as reduction. Because
of their electron-accepting character, fullerenes, and their derivatives
have been extensively investigated as electron-transporting materials
in organic thin-film transistors and organic photovoltaics.
*Nevertheless, fullerenes are an anomalous class of materials compared
with any other conventional organic electron-acceptors, due to their
robustness toward accepting multiple electrons.
Theoretical
chemists have proposed three possible factors that might be behind
fullerene’s electron-accepting ability:
--the high symmetry of the entire
molecule,
--its carbon atoms with pyramidally arranged bonds,
--and the
presence of pentagonal substructures distributed among six-membered
rings.
----The Kyoto team focused on the influence of the pentagonal
rings.
They designed and synthesized flattened fragments of fullerene,
and experimentally confirmed that these molecules could accept up to an
equal number of electrons as the number of five-membered rings in their
structure without decomposition.
“This surprising discovery
highlights the crucial significance of the pentagonal substructure for
generating stable multi-electron accepting systems,” says Fukazawa.
--Experiments
also revealed that the fragments display enhanced absorbance of
ultraviolet, visible, and near-infrared light compared to a more limited
absorbance by fullerene itself." SciTechDaily
