NMR diffusometry and conductometry study of the host–guest association between β-cyclodextrin and dodecane 1,12-bis(trimethylammonium bromide)

Surfactants form association complexes with cyclodextrins. In the present investigation we have used NMR-diffusometry and electrical conductivity to follow the interactions which take place between β-cyclodextrin and a bolaform surfactant: dodecane 1,12-bis(trimethylammonium bromide). Both 1H NMR self-diffusion and conductometry data indicate the formation of a 1:1 inclusion complex. Assuming this stoichiometry, it was possible to calculate the association constant; from the analysis of the self-diffusion coefficients of free β  -cyclodextrin and the bolaform surfactant an association constant K=3×103M−1 was obtained while the analysis of conductivity data gave a comparable value of K=2.5×103M−1.

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