Halogen vs hydrogen bonding in thiazoline-2-thione stabilization with σ- and π-electron acceptors adducts: Theoretical and experimental study

Abstract

Molecular charge-transfer complexes (CT) between thiazoline-2-thione (THZ) and different σ- (I2) and π-acceptors (Tetracyanoethylene (TCNE), 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ), and 2,3,5,6-tetrachloro-1,4-benzoquinone (CHL)) were investigated. UV–Vis absorption spectroscopy and theoretical calculations using both MP2/aug-cc-pVDZ-PP and B3LYP/6-311++G(d,p) level of theory were corroborated to study the nature of the stabilizing forces for THZ-I2, THZ–DDQ, THZ–TCNE, and THZ–CHL. Halogen bonding (XB) was the stabilizing attractive force in THZ-I2 and THZ–CHL whereas; hydrogen bonding (HB) was dominated in both THZ–TCNE, and THZ–DDQ complexes. Formation constant (K), extinction coefficient (ɛ), thermodynamic parameters such as enthalpy change (ΔH), entropy (ΔS), and Gibbs free energy (ΔG) were measured in different solvents.