Theoretical Study of the α-Cyclodextrin Dimer

• Published in: The journal of physical chemistry. A, Molecules, spectroscopy, kinetics, environment, & general theory Molecules, spectroscopy, kinetics, environment, & general theory, 2005-04, Vol.109 (14), p.3209-3219
• Main Authors: Nascimento, Clebio S., Anconi, Cleber P. A., Dos Santos, Hélio F., De Almeida, Wagner B.
• Format: Article
• Language: English
• Subjects: alpha-Cyclodextrins - chemistry; Computer Simulation; Dimerization; Models, Molecular; Thermodynamics
• ISSN: 1089-5639; 1520-5215
• DOI: 10.1021/jp044490j

The molecular structure, stabilization energy, and thermodynamic properties of the plausible modes of the interaction for the three possible α-cyclodextrin (α-CD) dimers (head-to-head, tail-to-tail, and head-to-tail) with a water cluster were obtained using quantum chemical methods for the first time. Nine distinct spatial arrangements were investigated. The head-to-head mode of interaction with water is preferred by more than 10 kcal·mol-1 (BLYP/6-31G(d,p)//PM3 Gibbs free energy difference value at room temperature) in relation to the next stable structure, with a water dimer structure placed inside each cavity and cyclic water tetramers surrounding each tail end. The inter α-CD hydrogen bonds play a major role to stabilize the dimeric structures, with no water tetramer being found between the two α-CD subunits for the preferred global minimum structure. Therefore, a theoretical model aimed to describe the behavior of α-CD dimer, or their inclusion complexes, in the aqueous media should take into account this preference for binding of the water molecules.