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Web Date: June 5, 2012

Cheap And Fast Way To Purify Metallofullerenes

Chemical Separations: Lewis acids could help researchers quickly separate metallofullerenes from fullerenes
Department: Science & Technology
News Channels: Materials SCENE, Analytical SCENE, JACS In C&EN
Keywords: metallofullerene, fullerene, MRI contrast agent, solar cell, Lewis acids
Metal Detector
About 18 TiCl4 ¬molecules (yellow) bind to C82 buckyballs (light blue), but only when a gadolinium atom (not shown) is trapped inside.
Credit: J. Am. Chem. Soc.
Structure of TiCl4 bound to C82 filled a gadolinium atom.
Metal Detector
About 18 TiCl4 ¬molecules (yellow) bind to C82 buckyballs (light blue), but only when a gadolinium atom (not shown) is trapped inside.
Credit: J. Am. Chem. Soc.

Japanese researchers have developed a simple method to purify metallofullerenes in minutes (J. Am. Chem. Soc., DOI: 10.1021/ja3030627). The new technique could make the materials attractive for applications in medicine and electronics, the researchers say.

Metallofullerenes are fullerenes, or buckyballs such as C¬70, with metal atoms trapped inside the carbon cage. Based on the materials’ electronic properties, chemists have thought that metallofullerenes could be used as contrast agents for magnetic resonance imaging or as components of flexible solar cells. But separating fullerenes that hold a metal atom inside from those that don’t requires many cycles of purification using high-performance liquid chromatography. As a result of this costly and time-intensive process, the materials’ promise has largely gone unfulfilled, says Hisanori Shinohara of Nagoya University, in Japan.

Shinohara and his coworkers have found a much simpler separation process that doesn’t involve HPLC. They had read reports that Lewis acids prefer to bind to metal-holding buckyballs than to bind to empty ones (Inorg. Chem., DOI: 10.1021/ic9017147). Intrigued, the team decided to test the ability of six metal halides to purify 10 metallofullerenes, such as C82 containing a gadolinium atom.

Titanium tetrachloride, which is a liquid at room temperature, worked the best by far. Minutes after the chemists added a few drops of TiCl4 to mixed solutions of metallofullerenes and metal-lacking fullerenes, a metallofullerene-TiCl4 complex precipitated out of the organic solvents. The scientists could easily remove the bound TiCl4 by washing the precipitate with water.

At the end of the process, which usually took less than 10 minutes, the metallofullerenes had purities greater than 99%, similar to the levels obtained by HPLC methods. The efficiency of the reaction depended on the oxidation potential of the metallofullerene: Materials with higher oxidation potentials were more difficult to purify.

Besides being faster, the TiCl4 purification method costs about 1/100 as much as HPLC methods, says Shinohara. The team has patented the process and hopes to work with a company to develop a commercial application.

Chemical & Engineering News
ISSN 0009-2347
Copyright © American Chemical Society
carbon (Wed Jun 06 05:17:07 EDT 2012)
that's a very great story!!!

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