Tiny bond makes big news

Chemists from UD, in collaboration with a colleague at the University of Wisconsin, recently set a new world record for the shortest chemical bond ever recorded between two metals, in this case two atoms of chromium.

The distance? A minuscule 1.803 Ångstroms, which is on the order of a billionth of the thickness of a human hair.
Of course, records are made to be broken. Klaus Theopold, professor and chairperson of UD’s Department of Chemistry and Biochemistry, says a Taiwanese research group soon is expected to report an even shorter metal-metal bond, also using chromium.

Theopold and his colleagues weren’t motivated by the Guinness Book of World Records or even a friendly bet. As is often the case in science, they discovered the molecule, which has a fivefold bond, quite by accident.

“Sometimes things like this just happen,” Theopold says.

He and Kevin Kreisel, who earned his doctorate from UD last year and now is a postdoctoral researcher at the University of Wisconsin, made the finding, working with research associate Glenn Yap and postdoctoral fellow Olga Dmitrenko, both from UD, and Clark Landis at the University of Wisconsin.

The research was reported in the Journal of the American Chemical Society.
For some time, Theopold has been researching the chemistry of chromium, a metal that’s an important industrial catalyst for making plastics such as polyethylene. “We discovered this interesting-looking molecule and realized that it had an extremely short distance between the metal atoms,” he says.

Using an analytical technique called X-ray diffraction, the scientists were able to look directly at the atomic structure of the new molecule and measure the distance between the chromium atoms.

“This molecule is probably not practically useful. We’re not going to get a patent here or cure cancer,” Theopold says. “Records define the range in which things can exist. It’s just an interesting molecule from a fundamental scientific standpoint.”

Before the latest discoveries, he says, the last record, achieved by researchers at Texas A&M University, stood for nearly 30 years.