The team--led by Guy Bertrand of both the University of California, Riverside, and Paul Sabatier University, Toulouse, France--predicted that the compound would be stable as a singlet 1,3-diradical [Science, 295, 1880 (2002)].

Singlet 1,3-diradicals are short-lived because the free electrons tend to form bonds. Previously, the longest lifetime observed at room temperature was on the order of microseconds.

Singlet radicals that can be handled under standard conditions could pave "the way for new developments in various fields," the researchers point out. In a commentary, Curt Wentrup, at the University of Queensland, in Australia, concurs. Molecules containing many nonbonding electrons could lead to new superconducting materials or compounds with magnetic properties, he writes.

In the new diradical, electrostatic repulsion of the negative charges on the boron atoms prevents bond formation. In addition, low-lying s* orbitals at the phosphorus atoms stabilize the radical sites. "The substituents were selected to reinforce both these effects," Bertrand explains.

At room temperature, the compound exists as yellow crystals, which melt at 212 º C without apparent decomposition. Protected from air and moisture, the crystals are stable for a couple of months, Bertrand says. Solutions can keep for one week in a refrigerator or overnight at room temperature. The color disappears when the material is exposed to air.

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