Aggregation and Host–Guest Interactions in Dansyl-Substituted Poly(acrylate)s in the Presence of β-Cyclodextrin and a β-Cyclodextrin Dimer in Aqueous Solution: A UV–Vis, Fluorescence, ¹H NMR, and Rheological Study

Abstract

The use of fluorescent polymers has been reported in studies of scintillators, 1 luminescent solar concentrators, 2 laser-resistant materials, 3 fiber-optic sensors, 4 and laser dyes. 5 Such polymers usually consist of a backbone substituted with fluorophores such as the naphthyl, 6À9 pyrenyl, 7,10À14 and dansyl 8,15À19 entities. The fluorescence intensities and lifetimes of such fluorophores are sensitive to local environment such that steady-state and time-dependent fluorescence studies have provided considerable insight into polymer interactions. 6À19 As part of an exploration of substituent interactions of randomly substituted poly(acrylate)s, PAA, 20À25 we report a UVÀvis, steady-state, and time-resolved fluorescence and 2D 1 H NOESY NMR study of the variation of dansyl substituent spectroscopic response to environmental change at the molecular level in dilute aqueous solution. These observations are used to interpret macroscopic observations gained through rheological studies of variations in the viscosities in terms of network formation in more concentrated solutions. The poly(acrylate)s studied are 3% randomly substituted by N-(2-aminoethyl)-, N-(6-aminohexyl)-, and N-(12-aminododecyl)-5-dansylsulfonamide, PAADSen, PAADShn, and PAADSddn, in which the dansyl substituent tether length progressively increases (Scheme 1). This facilitates studies of the effect of tether length on dansyl substituent, aggregation and complexation by β-cyclodextrin, βCD, and the linked dimer N,N 0 -bis(6 A -deoxy-6 A -β-cyclodextrin)urea, 66βCD 2 ur, in dilute aqueous solution where interactions occur dominantly within individual substituted poly(acrylate) strands.In more concentrated solutions aggregation of dansyl substituents between substituted poly(acrylate) strands occur to form networks which may either be disrupted through βCD forming

Design and Function of Supramolecular Recognition Systems Based on Guest-Targeting Probe-Modified Cyclodextrin Receptors for ATP

“…In NOESY measurements, protons that are in close proximity to each other give rise to correlation peaks. , According to Figure (i), there are correlations between 1 H derived from the dpa–azobenzene unit and H3 derived from the inside cavity of CyD in the presence of 1 equiv of ATP (enclosed in blue circles). The results suggested that conformations including and excluding the CyD-dpa-azobenzene unit exist in equilibrium in solution .…”

Development of Dipicolylamine-Modified Cyclodextrins for the Design of Selective Guest-Responsive Receptors for ATP

“…We also analyzed the supramolecular conformation of the ATP/ Cu·1 β complex by conducting nuclear Overhauser effect spectroscopy (NOESY) measurements of complex Cu·1 β. In the NOESY measurements, protons in close proximity to each other give rise to correlation peaks [ 43 , 44 ]. Correlations between the protons derived from the adenine moiety of ATP (α and β) and the protons derived from the inside cavity of CyD (H3 and H5) were observed ( Figure 7 ).…”

Reversible photo-responsive vesicle based on the complexation between an azobenzene containing molecule and α-cyclodextrin

“…The model used to determine the apparent complexation constant assumed that an equilibrium exists between a-CD, trans Azo-Cl and their complex formed as a host-guest 1 : 1 complex. 44 Therefore, a-CD complexed trans Azo-Cl according to eqn (4). The apparent complexation constant, K, at equilibrium was given by…”