Halogen Substituent Effects on the Relative Stability of Salicylidene Aniline Crystals of Different Stacking Types

Halogen substitution of N-salicylideneaniline (SA) molecules enables the modulation of intermolecular interaction modes, thereby allowing control over the structure of polytypic crystals with different stacking sequences. In crystals of halogen-substituted SA containing I or Br, type-II halogen bonding was observed in both I/I and Br/Br interlayer interfaces, while the symmetry of atomic arrangements at the stacking interfaces differed. Accordingly, we defined the Br/Br interlayer structure with C2 axis as type-IIa, and the I/I interlayer structure with 21 screw axis as type-IIb. In this study, we examined the relationship between halogen species and the stability of stacking interface structures for a polytype library of dihalogen-substituted SA using DFT calculations.