Ab Initio Approach to the Structure, Vibrational Properties, and Electron Binding Energies of H2S•••SO2

The present study employs high-level ab initio calculations to investigate the structure, vibrational frequencies, and electronic properties of H2S<middle dot> <middle dot> <middle dot>SO2. The analysis of vibrational frequencies reveals an intramolecular vibrational energy transfer phenomenon, where energy from the stretching modes of H2S is transferred to the v1s mode of SO2. At the CCSD(T)/aug-cc-pVQZ level, the interaction energy between H2S and SO2 is predicted to be 2.78 kcal/mol. Electron propagator theory calculations yield a HOMO-LUMO gap of 8.24 eV for H2S<middle dot> <middle dot> <middle dot>SO2. Furthermore, by utilizing ab initio results for the adiabatic ionization energy and electron affinity, the electrophilicity of H2S<middle dot> <middle dot> <middle dot>SO2 is estimated to be 2.01 eV. This value is similar to the electrophilicity of SO2, suggesting comparable reactivity and chemical behavior. The non-covalent interaction (NCI) analysis of the H2S<middle dot> <middle dot> <middle dot>SO2 complex emphasizes the significant contribution of non-covalent van der Waals interactions in its energetic stabilization.