Fri, Oct 17, 2008 - Page 1 News List

Local scientist and tiny bonds make for big discovery

By Meggie Lu  /  STAFF REPORTER

The miniscule distance of 0.01 angstrom — or 10-12 meters — has helped a young Taiwanese scientist bag the science equivalent of an “Olympic gold medal” in the global race to find the shortest metal-metal bond in chemistry. The feat has also helped Taiwan gain some recognition on the international scientific stage.

The achievement, reported in the renowned magazine Science and the journal Nature, came this year when Tsai Yi-chou (蔡易州), an associate chemistry professor at National Tsing Hua University (NTHU), synthesized a stable quintuple-bonded dichromium complex (a molecule that contains two chromium atoms that has five metal-metal bonds between them).

Tsai’s discovery broke a four-decade stagnation in chemistry where scientists were previously only able to make very short quadruple-bonded metal-metal bonds, the National Science Council (NSC) said at a press conference yesterday.

Though the compound has yet to find industrial or commercial application, its academic implications are profound, the NSC said, adding that Tsai’s breakthrough was published this August in Germany’s Angewandte Chemie as well as the Journal of the American Chemical Society.

In the past century, scientists had always believed that the more bonds that exist between two atoms, the shorter the bond distance would be, Tsai said.

In 2005, a quintuple-bonded dichromium compound was synthesized by Philip Power and colleagues, but the bond distance was 1.83 angstrom, Tsai said.

“Inorganic chemists have long thought that the fewer ligands on metal atoms, the better [stronger and shorter] a quintuple-bonded compound could be made … However, we made our compound with two or three ligands attached to each of our chromium atoms and the bond distance is 1.74 angstrom,” Tsai said.

Quoting US chemist Klaus Theopold, the record would be very difficult to break, as 1.74 angstrom may very well be the limit for the shortest metal-metal bond, he said.

Though Rhett Kempe, a professor at Germany’s Bayreuth University, had also submitted a quintuple-bonded compound to Angewandte Chemie in August, his chromium-chromium bond was 1.75 angstrom, the NSC said.

“My work focuses on the chemistry of low-valent and low-coordinate [or “coordination unsaturated”] transition metal complexes,” Tsai told reporters.

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