Aggregation and Host鈥揋uest Interactions in Dansyl-Substituted Poly(acrylate)s in the Presence of 尾-Cyclodextrin and a 尾-Cyclodextrin Dimer in Aqueous Solution: A UV鈥揤is, Fluorescence, 1H NM
文摘
A UV鈥搗is, steady-state, and time-resolved fluorescence 2D 1H NOESY NMR spectroscopic and rheological study of new poly(acrylate)s 3% randomly substituted with either N-(2-aminoethyl)-, N-(6-aminohexyl)-, or N-(12-aminododecyl)-5-dansyl-sulfonamide to give the substituted polymers PAADSen, PAADShn, and PAADSddn, respectively, is reported. Their dansyl substituent aggregation and complexation by 尾-cyclodextrin, 尾CD, and its covalently linked dimer N,N鈥?bis(6A-deoxy-6A-尾-cyclodextrin)urea, 66尾CD2ur, is also reported. The 尾CD complexation of the dansyl substituents is characterized by apparent complexation constants, K = 89, 105, and 55 dm3 mol鈥? for PAADSen, PAADShn, and PAADSddn, respectively, and the analogous complexations by 66尾CD2ur are characterized by K = 3.04 脳 103, 3.42 脳 104, and 2.42 脳 105 dm3 mol鈥? at pH 7.0 in aqueous 0.10 mol dm鈥? NaCl at 298.2 K. Under the same conditions the dansyl substituent shows three fluorescence decay constants assigned to the aggregated (蟿1 = 2.2, 2.5, and 3.2 ns), single (蟿2 = 5.0, 5.3, and 9.5 ns), 尾CD (蟿3 = 13.2, 11.7 ns, and undetected), and 66尾CD2ur complexed dansyl substituent states (蟿3 = 13.9, 20.8, and 19.3 ns) where the values in each data set correspond to PAADSen, PAADShn, and PAAddn solutions, respectively. 2D 1H NOESY NMR spectroscopy provides additional insight into dansyl substituent complexation by 尾CD and 66尾CD2ur, as do rheological studies. These data are interpreted in terms of the factors affecting dansyl substituent fluorescence quenching and the impact of tether length on dansyl substituent aggregation, complexation, and network formation.