On the Bonding Nature of Ozone (O3) and Its Sulfur-Substituted Analogues SO2, OS2, and S3: Correlation between Their Biradical Character and Molecular Properties
We investigate the bonding mechanism in ozone (O3) and its sulfur-substituted analogues, SO2, OS2, and S3. By analyzing their ground-state multireference configuration interaction wave functions, we demonstrate that the bonding in these systems can be represented as a mixture of a closed-shell structure with one and a half bonds between the central and terminal atoms and an open-shell structure with a single bond and two lone electrons on each terminal atom (biradical). The biradical character (β) further emerges as a simple measure of the relative contribution of those two classical Lewis structures emanating from the interpretation of the respective wave functions. Our analysis yields a biradical character of 3.5% for OSO, 4.4% for SSO, 11% for S3, 18% for O3, 26% for SOO, and 35% for SOS. The size/electronegativity of the end atoms relative to the central one is the prevalent factor for determining the magnitude of β: smaller and more electronegative central atoms better accommodate a pair of electrons facilitating the localization of the remaining two lone π-electrons on each of the end atoms, therefore increasing the weight of the second picture in the mixed bonding scenario (larger β). The proposed mixture of these two bonding scenarios allows for the definition of the bond order of the covalent bonds being (3-β)/2, and this accounts for the different O–O, S–S, or S–O bond lengths in the triatomic series. The biradical character was furthermore found to be a useful concept for explaining several structural and energetic trends in the series: larger values of β mark a smaller singlet–triplet splitting, closer bond lengths in the ground 1A' and the first excited 3A' states, and larger bond dissociation and atomization energies in the ground state. Finally, the latter explains the relative energy difference between the OSS/SOS and OOS/OSO isomers due to their different β values.
- Research Organization:
- Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC05-76RL01830
- OSTI ID:
- 1129334
- Report Number(s):
- PNNL-SA-98997; KC0301020
- Journal Information:
- Journal of the American Chemical Society, Vol. 136, Issue 7; ISSN 0002-7863
- Publisher:
- American Chemical Society (ACS)
- Country of Publication:
- United States
- Language:
- English
Similar Records
Sulfur X-Ray Absorption And Vibrational Spectroscopic Study of Sulfur Dioxide, Sulfite, And Sulfonate Solutions And of the Substituted Sulfonate Ions X(3)CSO(3-)(X = H, Cl, F)
Valence bonds in the main group elements. 2. The sulfur oxides