Endohedral metallofullerenes: Metallic Clusters inside fullerene cages (Campus Seminar)

Harry C. Dorn (Department of Chemistry, Virginia Tech, USA)

Location: Sala de Graus, Facultat de Química
Start time: Oct. 13, 2010, 11:30 a.m.

Abstract

Since the discovery of fullerenes 25 years ago, a plethora of new carbonaceous nanomaterials have been discovered including endofullerenes, nanotubes, nanohorns and graphene. Although the field of fullerenes, endohedral fullerenes, nanotubes and nanohorns is still relatively new, it is clear that there are a number of potential applications in diverse areas for these exciting new carbonaceous materials. Of special interest to our laboratory at Virginia Polytechnic and State University are the encapsulation of metals in fullerenes (endohedral metallofullerenes). Metallofullerenes, because of their shapes, capacity for multiple endo-encapsulants, isolation from the bio-environment and exo-functionalizability, are interesting constructs to study from a fundamental and practical application perspective. Over 10 years ago, we reported a family of very stable metal endohedral metallofullerenes (EMFs), A 3-x B x N@C 80 (x=0-3, A,B=metals) that are formed via a trimetallic nitride template (TNT) process.2 During the last 5 years, this family of new nanomaterials has greatly expanded and provides new research opportunities. In this presentation, we will describe recent results obtained for these new carbonaceous nanomaterials and their potential applications.

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About Harry C. Dorn

Institution: Department of Chemistry, Virginia Tech, USA

Dr. Harry C. Dorn joined the faculty at Virginia Polytechnic Institute & State University (VT) in 1974 and initiated a research program that involved analytical applications and development of NMR techniques including direct coupling of high-performance liquid chromatography and nuclear magnetic resonance (HPLC-NMR) [Analytical Chemistry, 1980]. Today, the HPLC-NMR technique has evolved as an important multi-million dollar tool in the pharmaceutical and bio-medical fields [Analytical Chemistry, 1984]. In the mid-1980’s, the Dorn laboratory initiated a second research area involving electron paramagnetic resonance (EPR) and dynamic nuclear polarization (DNP). These later studies provided new insight toward understanding fundamental nuclear/electron interactions. In these spectroscopic studies, weak intermolecular bonding interactions (e.g. hydrogen bonding) are studied for intermolecular liquid/liquid, solid/liquid and solid/solid interfaces. Recently, the DNP work has led to new approaches for next-generation magnetic resonance imaging (MRI) instruments currently under development at various sites (GE, Siemens, MIT, UCSB and other academic institutions).

In the early 1990’s, the Dorn laboratory also began a new area of research involving the synthesis, separation and functionalization of the newly discovered carbonaceous nanomaterials, nanotubes, fullerenes and metal-encapsulated fullerenes (endohedral metallofullerenes). In collaboration with Don Bethune and other scientists at IBM (Almaden), seminal papers involving the first bond length measurements and the corresponding solid-state dynamics of the soccer ball-shaped fullerene C60 were published [Science, 1991]. In a collaborative study by VT, the IBM group and Silvera (Harvard), a new phase of carbon was reported by collapse of solid C60 [Physical Review, 1992]. Later, the IBM team and the Dorn laboratory at VT published the first direct confirmation of metal encapsulation in a fullerene cage, Sc2@C84 [Nature, 1994]. In 1999, Dorn and Steven Stevenson (VT) discovered a new family of trimetallic nitride template (TNT) endohedral metallofullerenes A3N@C80 (A=Group IIIB and rare-earth metals) [Nature, 1999]. The trimetallic nitride templated endohedral metallofullerene technology has been licensed to Luna Innovations (Roanoke, VA) and a plant to manufacture these materials, Luna nanoWorks, is in Danville, VA.

In collaboration with P.W. Fowler (University of Exeter), the Dorn Group reported the first family of non-classical endohedral metallofullerenes, A3N@C68, that are exceptions to the well-known isolated pentagon rule (IPR) [Nature, 2000]. In collaboration with Alan Balch (University of California, Davis), x-ray structural studies of other cage TNT endohedral metallofullerenes, A3N@C78 [Angewandte Chemie, 2001] and mixed TNT derivatives ErSc2N@C80 [Journal of the American Chemical Society, 2001] were reported.

The Dorn Group et al reported the first exohedral organic functionalization of a TNT endohedral metallofullerene, Sc3N@C80 [Journal of the American Chemical Society, 2002]. In collaboration with H.W. Gibson (VT), the Dorn Group reported a unique chemical separation of these TNT endohedral metallofullerenes, A2N@C80, based on selective chemical reactivity [Journal of the American Chemical Society, 2005]. In collaboration with Panos Fatouros, Jim Tatum and Bill Broaddus (Virginia Commonwealth University), the Dorn Group published the first in vitro and in vivo results utilizing TNT endohedral metallofullerenes as next-generation MRI contrast agents. These agents exhibit MRI contrast images 25-30 times superior to commercial agents [Radiology, 2006]. Recently, the Dorn Group and Professor Alan Balch (University of California, Davis) have discovered a new non-spherical fullerene cage, namely a “BuckyEgg”, ellipsoidal Tb3N@C84 molecule. Websites containing information about the BuckyEgg have been viewed more than 30,000 times [Journal of the American Chemical Society, 2006]. The Dorn Group and Alan Balch have also recently reported a new class of metalloheterofullerenes, M2@C79N [Journal of the American Chemical Society, 2008].

In 2009, the Dorn laboratory (in collaboration with scientists at Medical College of Virginia [MCV]) reported a remotely new class of radiolabeled fullerenes, extensively reported in the news.

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