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((2^Adextrin)-S,3^AS)-3^A-deoxy-3^A-β-cyclodextrin)succinamide, 33βCD₂su, N-((2^AS,3^AS)-3^A-deoxy-3^A-β-cyclodextrin)N′-(6^A-deoxy-6^A-β-cyclodextrin)urea, 36βCD₂su, N,N-bis(6^A-deoxy-6^A-β-cyclodextrin)succinamide, 66βCD₂su, N-((2^AS,3^AS)-3^A-deoxy-3^A-β-cyclodextrin)-N′-(6^A-deoxy-6^A-β-cyclodextrin)urea, 36βCD₂ur, and N,N-bis(6^A-deoxy-6^A-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.