Cooperative Binding of 6-(p-Toluidinyl)naphthalene-2-sulfonate by β-Cyclodextrin Dimers

A fluorimetric study shows that 6-( p -toluidinyl)naphthalene-2-sulfonate (TNS - ) forms binary complexes with dimeric N, N ‘-bis(6 A -deoxy-6 A -β-cyclodextrin)glutaramide and its succinamide, malonamide, oxalamide, and urea analogues characterized by stability constants 13 010 ± 20, 16 700 ± 20, 11 000 ± 10, 32 640 ± 90, and 45 230 ± 70 dm 3 mol -1, respectively, in aqueous phosphate buffer at pH 7.0, I = 0.10 dm 3 mol -1 and 298.2 K. These values are substantially greater than that for the β-cyclodextrin·TNS - complex and are indicative of collaborative binding in the β-cyclodextrin dimer complexes. The factors affecting the stabilities of the cyclodextrin dimer complexes and their fluorescence characteristics are discussed, and comparisons are made with related systems.