Unexpected binding mode of gemini surfactants and γ-cyclodextrin: DOSY as a tool for the study of complexation

Diffusion-ordered NMR measurements for aqueous solutions at 298 K containing oxyethylene spacer gemini surfactants (12-EOi-12), in the absence and presence of γ-cyclodextrin ( γ-CD), were analyzed to determine the binding mode of the complex, and the effect of the complexation on the aggregation. The analysis of the self-diffusion coefficients reveals the formation of complexes of 1:1 stoichiometry (12-EOi-12:γ-CD). This complexation is strong enough to destroy aggregates in an extension that confirms the 1:1 stoichiometry. The structure of surfactants and ROE enhancements point to a complex in which both hydrophobic chains thread one γ-CD.