Spectroscopic and thermal studies on the inclusion of trans‐cinnamic acid and a number of its hydroxyl‐derivatives with α, β and γ‐cyclodextrins molecules

Abstract

The inclusion compounds of α-, β-and γ -cyclodextrins (α-CD, β-CD and γ -CD) with trans-cinnamic acid (t-CIA), 3-hydroxytrans-cinnamic acid (t-3OHCIA), 4-hydroxy-trans-cinnamic acid (t-4OHCIA) and 3,4-dihydroxy-trans-cinnamic acid (t-3,4OHCIA) were prepared and characterized, in the solid state, by means of thermogravimetry and Raman spectroscopy. The effects of the inclusion process on the guest molecules and on the hydrogen bond interactions of the guest were studied by monitoring sensitive vibrational modes, such as C O, C C and ring C-H stretching modes.By combining Raman and TG data with ab initio calculations and information from CSD database on similar compounds, inclusion geometries for the different compounds are proposed. The size of the host cavity and the maximization of host/guest hydrogen-bonding contacts appear to be the main factors determining the inclusion geometries.

Inclusion compounds of phenol derivatives with cyclodextrins: a combined spectroscopic and thermal analysis

“…As previously found for other aromatic inclusion compounds, [10,12,15,27] the band profile in the γ CD•3MeOPh inclusion complex is more similar to the one of the pure guest, probably as a result of lower constraints imposed by the larger γ CD cavity.…”

Physicochemical Characterization of Cyclodextrin–Drug Interactions in the Solid State and the Effect of Water on These Interactions

“…Therefore, it is possible to obtain the speculation of the molar ratios of an inclusion complex by using TGA. In addition, spectral features observed in the well‐characterized regions of the Raman spectra were justified in terms of specific guest–host interactions for guest molecules encapsulated in CD cavities . Furthermore, the distinct behavior on inclusion in α‐, β‐, and γ‐CD was associated with the dimensions of these cavities.…”

“…Finally, an abrupt weight loss was observed because of the decomposition of melted β‐CD. As mentioned above, the percentages of mass loss yielded molar ratios, which corresponded to the host/guest/H 2 O stoichiometries . Therefore, it is possible to obtain the speculation of the molar ratios of an inclusion complex by using TGA.…”

“…etc.) and aromatic CH bond stretching vibrations . This enables a vibrational study of guest molecules without spectral interference from the vibrational bands of the CD host on the selection of guest molecules showing vibrational bands in these spectral windows …”

“…The effects of the inclusion on guest molecules and hydrogen bond interactions were studied by monitoring sensitive vibrational frequencies, such as CO, CC, and aromatic CH stretching modes. In the crystal structure of the β‐CD–t‐CIA complex, t‐CIA molecules adopted an s‐trans orientation and β‐CD molecules stacked in a head‐to‐head arrangement . Although t‐CIA carboxylate groups were too far apart to form hydrogen‐bonded dimers, they formed OH···O hydrogen bonds with entrapped water molecules lying in the interdimeric space of the hydrophobic channel.…”