Cooperative binding of 6-(p-toluidinyl)naphthalene-2-sulfonate by beta-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)-beta-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 beta-cyclodextrin . TNS- complex and are indicative of collaborative binding in the beta-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.