Theoretical AM1 studies of inclusion complexes of alpha- and beta-cyclodextrins with methylated benzoic acids and phenol, and gamma-cyclodextrin with buckminsterfullerene

Semiempirical AM1 calculations have been performed on the inclusion complexes of alpha- and beta-cyclodextrin with benzoic acid and phenol and beta-cyclodextrin with methylated benzoic acids in the ''head first'' and ''tail first'' positions. The results show that alpha-cyclodextrin complexes with phenol and benzoic acid guests in the ''head first'' position are more stable than in the ''tail first'' position, while beta-cyclodextrin complexes with the same guests prefer the ''tail first'' position. The preferred orientation for beta-cyclodextrin with methylated benzoic acids is determined by the position of the methyl substituent(s). In general, para-methyl benzoic acid derivatives prefer the ''tail first'' position. gamma-cyclodextrin forms a slightly unstable 1:1 complex with C-60 (3.4 kcal/mol), but two gamma-cyclodextrins provide enough stabilization by about 10 kcal/mol to ''cage-in'' the C-60.