Theoretical study on the structures, stabilities and electronic properties of S2 O5 2− isomers in the gas and solution phases

Different theoretical levels of theory including B3LYP/6-311 + G(3df,3pd), MP2/6-311 + G(3df,3pd), QCISD/6-311 + G(d,p), CBS-QB3 and CCSD(T)/6-311 + (d,p)//B3LYP/6-311 + G(3df,3pd) have been employed to determine the structures, relative stabilities, electronic properties and thermochemistry of the selected isomers in the gas phase and aqueous solution.

Atoms in molecules (AIM) method and natural bonding orbital (NBO) were used to characterize the origin of atomic bonds. The NBO and AIM calculations showed that the strength of S–O and S–S bonds in the (O3SSO2)2−, (O2SOSO2)2− and (OSOSO3)2− isomer are relatively weak and go toward dissociation to form , , SO− and radical anions.

For more confirmation, the dissociation equilibrium constant (K diss) of each isomer were calculated at 298 K and showed that by increasing the dielectric constant of the solvent, the stability of the isomer increases. Based on these result, the isomers are considerably unstable and dissociate in the gas phase compared with solution.