Para-halogenated benzaldehyde molecules included in cyclodextrins: a combined spectroscopic and thermal analysis

Abstract

The inclusion complexes of 4-X-benzaldehyde guests (X = F, Cl, Br) in alpha-, beta-and gamma-cyclodextrins (alphaCD, betaCD and gammaCD) were prepared and characterized by means of thermogravimetry, differential scanning calorimetry (DSC) and vibrational spectroscopy. The stoichiometry of the inclusion complexes ranges from 2:1 to 1:2, depending on the cavity size of the host. Sensitive vibrational modes such as C-O and ring CH stretching modes were used to monitor the effects of the inclusion process and to assess the preferred inclusion geometry for each host-guest pair. On the whole, the spectral observations suggest that the small alphaCD cavity imposes important structural restrictions on the guest molecule, while the larger gammaCD cavity allows lsquoliquid-typersquo intermolecular contacts. Copyright © 2005 John Wiley & Sons, Ltd.