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The infrared spectra of inclusion compounds of terephthalaldehyde and two aromatic esters with α- or β- cyclodextrin are studied. A wide range of temperatures provides significant modifications of the spectra which are explained by rotational isomerism of the guest molecule.

The investigation by FT-IR and Raman spectroscopy of several cyclodextrin inclusion complexes reveals structural features not readily accessible by other spectroscopic methods. Thus, the cis conformation of terephthalaldehyde dominates within the α-cyclodextrin cavity. The locked and unlocked acetate group of hydroquinone diacetate in β-cyclodextrin can be easily distinguished, while p-benzenedimethanol diacetate displays the features of a “solid solution”. Finally, the detection of hydrogen bonding in the α-cyclodextrin inclusion compound of butanediol diacetate brings to light even more complex supramolecular structures.