Crystal Structure of Iodinated Mesoionic Triphenylthiazol‐3‐ium‐4‐olates: Combination of Stacking and Halogen Bonding Interactions

The crystal structures of triphenylthiazol-3-ium-4-olates substituted with iodine atoms on different phenyl rings are investigated. Analysis of single molecule crystal structures reveals consistent torsion angles across all compounds. Specifically, excellent planarity with the mesoionic ring is achieved when the phenyl ring at the 5-position enables effective conjugation with the enolate moiety. Three types of halogen interactions are identified depending on the iodine substituent position: CO···I, π-electron···I, and I···I interactions. All crystal structures exhibited columnar stacking arrangements. Density functional theory calculations show that stacking interactions provide greater energetic stabilization than halogen bonds. Additionally, the columnar stacking arrangement is influenced by the nature of the halogen bonding.