Inclusion Behavior of β‐Cyclodextrin with Bipyridine Molecules: Factors Governing Host‐Guest Inclusion Geometries

Abstract

The 1:1 complexation of beta-cyclodextrin (beta-CD) with structurally similar bipyridine guests which lead to the formation of six inclusion complexes (1-6) of beta-CD with 4,4'-vinylenedipyridine, 2,2'-vinylenedipyridine, 1-(2-pyridyl)-2-(4-pyridyl)ethylene, 4,4'-ethylene-dipyridine, 4,4'-dithiodipyridine, and 2,2'-dithiodipyridine has been investigated comprehensively by X-ray crystallography in the solid state and by (1)H NMR spectroscopy and microcalorimetric titration in aqueous solution. The complex formation constants (K(S)) for the stoichiometric 1:1 host-guest inclusion complexation of beta-CD with the bipyridine derivatives were determined in aqueous solution by microcalorimetry and the host-guest inclusion geometries of the complexes were deduced from (1)H ROESY NMR spectroscopy. It transpires that the guest bipyridine molecules are included in the beta-CD cavity with a range of different inclusion geometries. In the solid state, the crystal superstructures for the beta-CD complexes 1, 4, and 5 are characterized by the triclinic crystal system (space group P1) commensurate with AAAA type supramolecular aggregation. By contrast, the beta-CD complexes 2, 3, and 6 display either monoclinic (space group P2(1)) or orthorhombic (space group C222(1)) crystal systems, characteristic of ABAB type supramolecular aggregation. The results demonstrate that the relative locations of the nitrogen atom positions and the bridge-bond links between the two pyridine rings in these bipyridine guests, not only lead to distinct crystal systems and space groups, but also to different binding geometries and thermodynamical parameters on complexation of the bipyridines with beta-CD. The knowledge obtained from this research improves our understanding of the molecular recognition and self-assembly processes exhibited by beta-CD, both in the solid state and in aqueous solution.

β-Cyclodextrin dimethylformamide 12.5 hydrate: a deeper insight into β-cyclodextrin crystal packing

“…It is rather the formation of the hydrogen-bonded network, and hence the location of hydration water molecules, which ultimately determines the separation between neighbouring 'herringbones'. Previous studies proposed that the formation of hydrogen-bonded networks in -CD complexes is highly influenced by the guest and that guests that are similar in size and shape can lead to unrelated hydrogen-bonded networks, unit cells and space groups (Zhao et al, 2009;Zhang et al, 2012). This idea is supported by observations on XEGTAF [see (vi)].…”

Cyclodextrins Initiated Ring-Opening Polymerization of Lactide Using 4-Dimethylaminopyridine (DMAP) as Catalyst: Study of DMAP/β-CD Inclusion Complex and Access to New Structures

“…This contrasts with the ability of lactones to form inclusion complexes with cyclodextrins, such as the ε-caprolactone/β-CD inclusion complex [ 24 ]. However, the inclusion of nitrogenous heterocyclic bases such as, e.g., adenine [ 25 ], bipyridines [ 26 ] or α-aminopyridine [ 27 ] into β-CD has been reported in the literature. As far as we know, inclusion complexes between DMAP and β-cyclodextrin have never been reported in the literature.…”

“…Based on the model study, we decided to synthesize the inclusion complex DMAP/β-CD by applying the synthesis in water, as reported for other similar inclusion complexes [ 26 , 27 , 30 ] (see experimental section). Entries representative of the polymerization of rac -lactide mediated by the inclusion complex are presented in Table 2 .…”

Determination of the Absolute Configuration of Aegelinol by Crystallization of Its Inclusion Complex with β-Cyclodextrin

“…The structure of the β-CD-aegelinol complex was solved by atomic coordination replacement methods using a β-CD complex structure from CSD [BOSZOZ] [40] with the same cell parameters after making suitable transformation and deleting the guest from the structure. Extra electronic density in the cavity corresponded to aegelinol.…”