Inorganic Polysulfides in Solution: Structural Properties and Conformational Isomerism

Abstract

We present a comprehensive theoretical examination of the structural properties of dianionic polysulfides [Sn]2– (n = 2–6), their conjugated monoacids [HSn]− (n = 2–6), and a selection of 1e–-oxidized radical anions [Sn]•– (n = 2–4), in aqueous and dimethyl sulfoxide (DMSO) solutions. We investigated the structures and stabilities of various conformational isomers within these families of compounds by employing Quantum Mechanics–Molecular Mechanics (QM-MM) Molecular Dynamics (MD) simulations. The explicit inclusion of solvent molecules in the calculations revealed stable conformational structures that were previously unreported and might have appreciable concentrations in real systems. The interconversions between the isomeric structures proceed on the order of hundreds of picoseconds and are energetically similar to the isomerization processes in substituted cyclohexanes. We also conducted a detailed analysis of the stability of different isomers of the radical anion [S4]•– in solution. Our findings highlight the significant influence of the solvent on the isomerizations, a result that could be particularly relevant for enhancing the performance of metal–sulfur batteries.