Protonation of the ozone analogue S2O: structures, energies and vibrational spectra of HS2O+ isomers

Abstract

Protonation is a simple reaction that can both reveal and induce changes in the electronic structure of molecules. The protonation of various S2O isomers: SSO, cyclic S2O, and SOS does not qualitatively change the underlying potential energy surface of these isomers. The protonated SSO isomers are lowest in energy, and cis-SSOH+ is the lowest of these. S-protonated and O-protonated cyclic S2O are next highest in energy, with the S-protonated isomer slightly lower in energy than the O-protonated isomer. For SOS we find, contrary to previous results, that the lowest energy isomer is a 3B2 rather than a 3A2 state. Protonated SOS, however, has a singlet ground state. Both geometry changes and vibrational frequency changes upon protonation illustrate the nature of the bonding in the various S2O isomers.