CNDO–MO Study of the Ozonide Ion and Related Species

The unpaired electron in the ozonide ion (O3−) is expected to occupy an antibonding molecular orbital; yet published experimental results indicate a shorter bond length and larger force constants than in neutral ozone. Molecular orbital calculations in the CNDO approximation are reported for this ion and related species (O3, SO2, SO2−, OF2+, OF2), using both the CNDO/2 and CNDO/BW parametrizations. Both methods predict that the bond lengths in O3− are 0.04 Å longer than in O3, in agreement with qualitative molecular orbital theory, and that the bond angle is 1° less than in O3. The CNDO/BW method predicts that the electron affinity of O3 is higher than that of the O atom, in agreement with experiment, since a stabilizing exchange effect outweighs the antibonding nature of the orbital occupied by the extra electron.