New all-metal molecules ape organics.

Researchers have stumbled upon the first all-metal molecules that seem to have properties like those of certain common carbon-based molecules, including some that underlie life and others widely used in industry.

The new metal structures show a tantalizing trait called aromaticity. This molecule-stabilizing property was named after the first such molecules identified, including benzene, which have noticeable aromas. But not all aromatics actually smell, and neither does this metallic newcomer, says Alexander I. Boldyrev of Utah State University in Logan. He and his colleagues report their finding in the Feb. 2 SCIENCE.

Last year, Boldyrev and his colleagues created the first flat, five-atom molecules with a carbon atom at the center. Normally, such combinations of atoms assume a tetrahedral shape. Following that accomplishment, the researchers sought to create related flat molecules--including one with four aluminum atoms linked to a different central metal atom, such as copper.

It didn't work, says team member Lai-Sheng Wang of Washington State University and the Pacific Northwest National Laboratory in Richland. Instead, they got something better.

When Wang beamed a laser at an aluminum-copper alloy, he created gaseous molecules that have pyramidal shapes--a perfect square of aluminum atoms attached to a copper atom at the apex. Wang's spectroscopy and Boldyrev's calculations revealed the product's unusual stability, as well as the presence of two so-called pi electrons, which are hallmarks of aromaticity.

The researchers have also made similar molecules with different apex atoms, such as lithium or sodium. They suspect they may be on to a large, new class of molecules. Some might eventually serve as the basis for novel materials with as-yet unimagined properties, Boldyrev says.