Thickness Recognition of Bolaamphiphiles by α‐Cyclodextrin

Abstract

The minimum internal diameters of alpha-, beta-, and gamma-cyclodextrin were calculated by a space filling algorithm, MolShape, from the electron density maps created by semiempirical AM1 and PM3 calculations using Gaussian03. In addition, the minimum diameters of a series of dicationic bolaamphiphiles were calculated by MolShape as well. The calculated diameters of these hosts and guests allowed prognosis about the stabilities of the corresponding inclusion compounds. The experimental binding data, obtained by isothermal titration calorimetry (ITC), revealed indeed a very pronounced thickness recognition and correlate well with the calculated diameters.

Solubilization of Polycyclic Aromatics in Water by γ‐Cyclodextrin Derivatives

“…The cross-sectional area A of the g-CD cavity was obtained by analysis of the electron density map of g-CD with the program MolShape, [22] which was already useful for prediction of stoichiometries of polyrotaxanes. According to this view, g-CD was selected as a simple model host throughout the theoretical calculations.…”

“…The calculated DG values of the aromatic guests with g-CD or g-CD derivatives are summarized in Table 7. [22] These entropic effects would also explain why the slim guest STI shows a strongly negative DG value, whereas its DE value is only moderate. Pronounced differences between the DG values were observed for the various guests.…”

Molecular solubilization of fullerene C60 in water by γ-cyclodextrin thioethers

“…CDs form water-soluble inclusion complexes with many hydrophobic or amphiphilic guest molecules [26], mainly driven by hydrophobic interactions [27]. Among the commercially available CDs, γ-CD with a clear width of d = 0.74 nm [28] is only large enough to partially accommodate C 60 , which has a still greater van der Waals diameter of 1.0 nm [2]. Molecular dynamics studies strongly favour a sandwich-like structure of the complex, in which two γ-CD molecules tightly interact through hydrogen bonds between their secondary rims and in which C 60 is situated in the middle at the widest sites of both CDs (see Fig.…”

Solid‐Phase Synthesis of Oligo(phenylene ethynylene) Rotaxanes

“…[15] bulky phenylene residue. [18] This is the first cyclodextrin [3]rotaxane to be formed selectively as the head-to-tail isomer; [19] previous examples have been synthesized as tailto-tail isomers (with both 6-rims at the center), [20,21] or as mixtures of stereoisomers. [22,23] This work represents the first solid-phase synthesis of a cyclodextrin rotaxane, the first solid-phase synthesis of any [3]rotaxane, and the first stereoselective synthesis of a cyclodextrin [3]rotaxane with a head-to-tail stereochemistry (with the 2,3-rims of both CDs pointing in the same direction).…”