The effect of the head-group spacer length of 12-s-12 gemini surfactants in the host-guest association with beta-cyclodextrin
Författare
Summary, in English
NMR spectroscopy has been used to study and characterize the interactions in solution between beta-CD and alkyl-alpha,omega-bis(dodecyldimethyl ammonium bromide) gemini surfactants with the following head-group spacer lengths: 2, 4, 6, 8, and 10. The application of the method of continuous variation gives as a result that 1:1 and 2:1 (beta-cyclodextrin-gemini) complexes are formed; the association stoichiometry is dependent on the spacer chain length, varying from 1.5 (for s = 2) to 1.8 (for s = 10). Assuming a two-step mechanism, the binding constants have been computed. In general, the overall binding constant slightly increases with an increase of the number of methylene groups in the spacer. The H-1 NMR spectra of the N-(CH3)(2) groups in beta-cyclodextrin/gemini mixed solutions are split into two peaks for 12-10-12, suggesting that the gemini spacer can thread the beta-cyclodextrin so that the latter is positioned between the gemini head-groups. Inspection of the ROESY spectra allowed the establishment of several spatial proximities between the protons from the beta-CD and the gemini and for a spacer length of 10, the data indeed indicate that complexes are formed with the CD molecule positioned between the two charged head groups with the spacer passing through the CD molecule. (C) 2010 Elsevier Inc. All rights reserved.
Avdelning/ar
Publiceringsår
2011
Språk
Engelska
Sidor
725-732
Publikation/Tidskrift/Serie
Journal of Colloid and Interface Science
Volym
354
Issue
2
Dokumenttyp
Artikel i tidskrift
Förlag
Elsevier
Ämne
- Physical Chemistry
Nyckelord
- Binding constants
- structures
- Supramolecular
- H-1 NMR spectroscopy
- Cyclodextrins
- Gemini surfactants
Status
Published
ISBN/ISSN/Övrigt
- ISSN: 1095-7103