title: Theoretical study of the alpha-cyclodextrin dimer.
abstract: The molecular structure, stabilization energy, and thermodynamic properties of the plausible modes of the interaction for the three possible alpha-cyclodextrin (alpha-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 alpha-CD hydrogen bonds play a major role to stabilize the dimeric structures, with no water tetramer being found between the two alpha-CD subunits for the preferred global minimum structure. Therefore, a theoretical model aimed to describe the behavior of alpha-CD dimer, or their inclusion complexes, in the aqueous media should take into account this preference for binding of the water molecules.
authors.affiliation: NEQC: Núcleo de Estudos em Química Computacional, Departamento de Química, ICE, Universidade Federal de Juiz de Fora (UFJF), Campus Universitario, Martelos, Juiz de Fora, MG, 36036-900, Brazil.
authors.forename: Clebio S
authors.initials: CS
authors.lastname: Nascimento
authors.forename: Cleber P A
authors.initials: CP
authors.lastname: Anconi
authors.forename: Hélio F
authors.initials: HF
authors.lastname: Dos Santos
authors.forename: Wagner B
authors.initials: WB
authors.lastname: De Almeida
mesh_terms: D003198:Computer Simulation; D019281:Dimerization; D008958:Models, Molecular; D013816:Thermodynamics; D047391:alpha-Cyclodextrins / Q000737:chemistry*
chemical_list: D047391:alpha-Cyclodextrins; C032613:alpha-cyclodextrin