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 S 2 O isomers: SSO, cyclic S 2 O, 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. Sprotonated and O-protonated cyclic S 2 O are next highest in energy, with the S-protonated isomer slightly lower in energy than the O-protonated isomer. For SOS we ® nd, contrary to previous results, that the lowest energy isomer is a 3 B 2 rather than a 3 A 2 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 S 2 O isomers.