Abstract
The stable isomers and electronic states of [S,S,N,O](-) species are investigated with a special focus on the most relevant isomers that could be involved in the NO/H2S cross-talk pathways in biological media. This work identifies eight stable anions, among which are the already known cis-SSNO- and trans-SSNO- molecules and a new NO3--like anionic species, NS2O-. Our computations show that the previously determined structure in lab experiment is trans-SSNO-, which is not relevant for biological activity in vivo. Instead, NS2O- is proposed as the most likely key intermediate in vivo during important biological processes. This result alleviates the corresponding controversy in the literature.