Researchers tore up a few pages of the chemistry rule book this year with the discovery of new types of bonds, electrical connections that hold molecules together. Most significant was the September unveiling by Japanese researchers of a powerful linkage between two silicon atoms that share three pairs of electrons—a so-called triple bond.
Chemists have long believed that elements heavier than neon could share only one pair of electrons. The discovery in 1981 of silicon-silicon and silicon-carbon double bonds showed that nature had more tricks in store and inspired a long, arduous search for even more elaborate triple bonds among the heavier elements. Akira Sekiguchi and his colleagues at the University of Tsukuba finally found this chemical connection when they altered a silicon compound to form a new material they call disilyne, an emerald-green crystal, and then illuminated it with X-rays to reveal the presence of triple bonds within. “This is a really important step forward,” says Robert West, a chemist at the University of Wisconsin who used to be Sekiguchi’s adviser. Polymers based on silicon-silicon or silicon-carbon triple bonds, he says, could possibly act as perfect electrical conductors, allowing the construction of extremely rapid digital circuits.
In parallel work, Mikhail Eremets of the Max Planck Institute for Chemistry in Germany found a novel bond between atoms of nitrogen, the most common element in Earth’s atmosphere. Unlike silicon, nitrogen normally forms a triple bond. But at high pressures and temperatures above 3,140 degrees Fahrenheit, nitrogen atoms transform into a polymer, a chain of single-bonded atoms. When polymeric nitrogen reverts back to its atmospheric form, Eremets believes, it should release a vast amount of energy—more than five times as much as TNT.