Lithium superoxide

Lithium superoxide (LiO₂) is an inorganic compound which has only been isolated in matrix isolation experiments at 15-40 K. It is an unstable free radical that has been analyzed using infrared (IR), Raman, electronic, electron spin resonance, soft X-ray spectroscopies, and a variety of theoretical methods.

Structure

Experimental studies indicate that the LiO₂ molecule contains highly ionic bonds. Eighteen different values were attained using six isotopic species. This indicated that the force constant between the two oxygen atoms corresponds with the constant found for the O₂⁻ ion. Studies indicate that there is little to no covalent character in the LiO₂ molecule.

The bond length for the O-O bond was determined to be 1.34 Å. Using a simple crystal structure optimization, the Li-O bond was calculated to be approximately 2.10 Å. Lithium superoxide is extremely reactive because of the odd electron present in the π* molecular orbital.

There have been quite a few studies regarding the clusters formed by LiO₂ molecules. The most common dimer has been found to be the cage isomer. Second to it is the singlet bypyramidal structure. Studies have also been done on the chair complex and the planar ring, but these two are less favorable, though not necessarily impossible.