Nowadays cyclodextrins, cyclic compounds consisted from α-D-glucopyranose connected through 1,4-glycosidic bonds, are one of the well studied class of “host” molecules [1]. β-Cyclodextrin, the most important homologue of this class formed by seven α-D-glucopyranose units, has wide application in chemistry, medicine and food industry [2]. It can be explained by its capability to form inclusion complexes of the host-guest type with many organic molecules (Fig.1, left). Therefore, it is very important to be able to predict the possibility of formation of β-cyclodextrin complexes [3].
The main purpose of this work is to evaluate the possibility of formation of β-cyclodextrin complexes with various organic molecules using geometric and quantum-mechanical methods.
We have evaluated the β-cyclodextrin cavity volume and volume of guest molecule with the Voronoi polyhedron method (Fig.1, right) as implemented in ToposPro [4]. Also we estimated the contribution of the geometrical factor in the adsorption process, and simulated the β-cyclodextrin complexation by AM1, PM3, HF/6-321G (d,p) and DFT methods with 1,3,5-trimethylbenzene, benzene, p-xylene, o-xylene, m-xylene, toluene, and ethylbenzene. The results obtained were compared with experimental absorption data.
It is shown that the Voronoi approach can be effectively used for predicting stability of β-cyclodextrin complexes; the prediction fits both quantum-mechanical modeling and the experimental results.
Fig. 1. A complex of β-cyclodextrin with 4,4'-diaminobiphenyl (left) and the Voronoi polyhedron of the 4,4'-diaminobiphenyl molecule included in the cavity of the β-cyclodextrin molecule (right).
The work was supported by the Russian government (Grant 14.B25.31.0005).
References
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