2023

Koivuporras, Alisa; Mailman, Aaron; Guo, Hongshuang; Priimagi, Arri; Puttreddy, Rakesh;

Thiophenes bearing monotopic and symmetric ditopic halogen substituents and asymmetric ditopic halogen and pyridine substituents that act as halogen bond acceptors were evaluated for their halogen bonding interactions with 1,4-diiodotetrafluorobenzene and N-iodosuccinimide. The combinations resulted in C/N–I···X′ (X′ = Cl, Br, I) and C/N–I···NPy (Py = pyridine) interactions, the former characterized by an interaction energy (ΔEint) ranging from −4.4 to −18.7 kJ mol–1 and the latter from −26.3 to −56.0 kJ mol–1. X-ray crystallography studies show that the ditopic asymmetric systems consisting of both halogens and pyridine self-associate through C–X···NPy (X = Cl, Br, I) halogen bonding, and in their optimized structures the energies range from −5.4 to −19.6 kJ mol–1 depending on the type of halogen atom present. The 1H NMR association constants of N–I···NPy halogen bonds range between 1405 and 6397 M–1. The σ-hole strengths of halogens have been useful in describing the interaction energies and solution models.