Complexation of 6-(4′-(toluidinyl)naphthalene-2-sulfonate by β-cyclodextrin and linked β-cyclodextrin dimers

Abstract

The complexation of 6-(4′-(toluidinyl)naphthalene-2-sulfonate, TNS−, by β-cyclodextrin (βCD) and five linked βCD-dimers is characterized by UV-Vis, fluorescence and 1H NMR spectroscopy. In aqueous phosphate buffer at pH 7.0, I = 0.10 mol dm−3 and 298.2 K, TNS− forms host–guest complexes with βCD of stoichiometry βCD·TNS− {K1 = [βCD·TNS−]/([βCD][TNS−]) = 3300 dm3 mol−1} and βCD2·TNS− {K2 = [βCD2·TNS−]/([βCD][βCD·TNS−]) = 11 dm3 mol−1} as shown by fluorescence studies. For N,N-bis((2Adextrin)-S,3AS)-3A-deoxy-3A-β-cyclodextrin)succinamide, 33βCD2su, N-((2AS,3AS)-3A-deoxy-3A-β-cyclodextrin)N′-(6A-deoxy-6A-β-cyclodextrin)urea, 36βCD2su, N,N-bis(6A-deoxy-6A-β-cyclodextrin)succinamide, 66βCD2su, N-((2AS,3AS)-3A-deoxy-3A-β-cyclodextrin)-N′-(6A-deoxy-6A-β-cyclodextrin)urea, 36βCD2ur, and N,N-bis(6A-deoxy-6A-β-cyclodextrin)urea, 66βCD2ur, the analogous K1 = 9600, 8700, 12 500, 9800, and 38 000 dm3 mol−1, respectively. 1H NMR ROESY studies provide evidence for variation of the mode of complexation of the TNS− guest as the host is changed. The factors affecting complexation are discussed and the synthesis of the new linked βCD-dimer 36βCD2su is reported.