NMR diffusometry and conductometry study of the host-guest association between beta-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 ss-cyclodextrm and a bolaform surfactant: dodecane 1, 1 2-bis(trimethylammonium bromide). Both H-1 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 ss-cyclodextrin and the bolaform surfactant an association constant K = 3 x 10(3) Mb(-1) was obtained while the analysis of conductivity data gave a comparable value of K = 2.5 x 10(3) M-1. (c) 2006 Elsevier Inc. All rights reserved.