Structures of inclusion complexes of halogenbenzoic acids and α-cyclodextrin based on AM1 calculations

Semi-empirical quantum mechanics calculations using AM1 (Austin Method 1) were carried out for various host-guest combinations of α-cyclodextrin and mono-halogen benzoic acids. The energetically favorable inclusion structures were identified. The AM1 results show that α-cyclodextrin complexes with mono-halogen benzoic acid acids (where the halogen is chlorine, bromide, iodine) as guest compounds are more stable in the "head first" position than in the "tail-first" position for meta and para isomers while ortho mono-halogen benzoic acids complexes with α-cyclodextrin are more stable in "tail-first" position. The calculated structures were found to be in good agreement with those obtained from crystalographic databases.