Polymorphism, pseudopolymorphism and amorphism of peracetylated alpha-, beta- and gamma cyclodextrins

Polymorphism, pseudopolymorphism, and amorphism of hexakis(2,3,6-tri-O-acetyl)--cyclodextrin (TACyD), heptakis(2,3,6-tri-O-acetyl)--cyclodextrin (TACyD), and octakis(2,3,6-tri-O-acetyl)--cyclodextrin (TACyD) were investigated using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), powder X-ray diffractometry (XRPD), Fourier transform infrared spectroscopy (FTIR) and optical microscopy. An anhydrous and a bi-hydrate crystalline forms of TACyD, two monotropic anhydrous polymorphs and three pseudopolymorphs (i.e. methanolate, hydrate, and isopropanolate-hydrate) of TACyD, as well as two monotropic anhydrous polymorphs and isostructural pseudopolymorphs (e.g. hydrate and isopropanolate-hydrate) of TACyD were isolated and characterized. The amorphous forms of each TACyD were also obtained. Thermal data for desolvation of TACyD·2H2O and TACyD·CH3OH were reconciled with their crystal packing features. Melting temperatures and enthalpies of the crystalline forms of each TACyD can be referred to for possible solid-state interactions with drugs.