Physicists Discover Theoretical Possibility of Large, Hollow Magnetic Cage Molecules

Physicists Discover Theoretical
Possibility of Large, Hollow
Magnetic Cage Molecules
July 31, 2013 — Virginia
Commonwealth University
researchers have discovered, in
theory, the possibility of creating
large, hollow magnetic cage
molecules that could one day be used
in medicine as a drug delivery system
to non-invasively treat tumors, and in
other emerging technologies.
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Approximately 25 years ago,
scientists first made the discovery of
C 60 fullerene -- better known as the
Buckminster Fullerene -- a molecule
composed of 60 carbon molecules
that formed a hollow cage. Due to its
unique hollow cage structure the
molecule offers serious technological
potential because it could hold other
atoms or small molecules inside, and
therefore, be used in applications
such as drug delivery.
That potential has since spurred
worldwide interest among scientists
who have been searching for similar
molecules. Although some hollow
cage structures have been found,
none of them is magnetic. Magnetic
properties of the structure are of
particular interest because a hollow
magnetic structure carrying an
embedded atom or molecule can be
guided by an external magnetic field
and may serve as an effective vehicle
for targeted drug delivery.
In a new study, published online on
July 22 in The Journal of Chemical
Physics, two VCU scientists employing
state-of-the-art theoretical methods
show that magnetic hollow cages
larger than the original C60 fullerene
that carry giant magnetic moments
are possible. A magnetic moment
refers to the measure of the
magnetic strength of a cluster.
"The potential benefit of this finding
is that it provides a route to the
synthesis of molecular magnets with
colossal magnetic moments," said co-
lead investigator Puru Jena, Ph.D.,
distinguished professor of physics in
the VCU College of Humanities and
Sciences. Jena collaborated with
Menghao Wu, Ph.D., co-author of
the paper and a postdoctoral scholar
in the VCU Department of Physics.
"These molecules can be used for
targeted non-invasive drug delivery.
When assembled, the molecules can
also form new high strength magnets
for device application," Jena said.
According to Jena, the pair of VCU
researchers demonstrated the
magnetic moment of the molecule by
focusing on hetero-atomic clusters
consisting of transition metal atoms
such as cobalt (Co) and manganese
(Mn) and carbon (C) atoms. In
particular, Co 12 C 6 , Mn 12 C6 , and
Mn 24 C 18 clusters consisting of 12
cobalt and six carbon atoms, 12
manganese and six carbon atoms,
and 24 manganese and 18 carbon
atoms, respectively, carry magnetic
moments as large as 14, 38 and 70
Bohr magnetons. In comparison, the
magnetic moment of an iron (Fe)
atom in crystalline iron is 2.2 Bohr
magnetons.
According to Jena, the team is still
early in its discovery process.
"There is a long way to go.
Experiments first have to be carried
out to prove the predictions of our
theory," said Jena.
"Ways must be found to synthesize
large quantities of these molecules
and study their magnetic properties
once they are assembled. Finally,
these molecules need to be
functionalized by embedding desired
atoms/molecules for practical
applications."