Carbonyl sulfide (OCS) is the most abundant and stable sulfur-containing triatomic gas present in the atmosphere that plays an important role in aerosol formation. Structure, energetics, and photoelectron spectral properties of the microhydrated OCS in its neutral and anionic forms have been studied by using the BP86, B3LYP, and MP2 methods. OCS is linear in the neutral state but bent in the anionic state. Water binds with the OCS through a single hydrogen bond (O-H···O) in the OCS-(H2O)n [n = 1-6], whereas binding of OCS(-) with water takes place through single as well as double hydrogen bonds (O-H···S and O-H···O). Energy decomposition analysis shows that electrostatic and exchange energies are the main contributors to the stabilization energy of the microhydrated OCS and OCS(-) clusters. Detachment as well as solvation energies are calculated with different levels of theory and compared with the existing experimental values. Finally, an analytical expression has been used to obtain the bulk value of the detachment and solvation energies from the existing information on the finite size clusters. The present study reveals that hydration increases the detachment energy of the OCS(-) by 3.2 eV. In the absence of experimental bulk values of the detachment and solvation energies for this system, the values obtained by the solvent-number-dependent theoretical expression will definitely reduce this gap and may be used for the modeling of the OCS in the atmosphere.

Structure, energetics, and vibrational frequency of the microhydrated carbonyl sulfide anion [OCS−(H2O)n (n = 1–6)] have been explored by the systematic ab initio study to have a comprehensive understanding about the hydration‐induced stabilization phenomenon of OCS−. Water binds with the OCS− in single hydrogen‐bonded (SHB) or double hydrogen‐bonded (DHB) fashion with OH ⋯S and OH ⋯O contacts. Maximum five water molecules can stay in a cyclic water network of these hydrated clusters forming interwater hydrogen bonding (IHB) with each other and out of this, maximum of two water molecules can bind directly to the OCS− in (DHB) arrangement. The stabilization energy values of OCS−(H2O)n depict that ion–water interaction is significant up to four water molecules and beyond that OCS− is stabilized by IHB between the water molecules. The CO stretching frequency of OCS− gets red shifted, whereas CS stretching frequency gets blue shifted on hydration. Charge analysis of hydrated clusters of OCS− indicates that negative charge moves toward oxygen from sulfur on hydration. © 2015 Wiley Periodicals, Inc.