A comparative study on inclusion complexation of substituted anilinonaphthalene sulfonic acids with 1,6,20,25-tetraaza[6.1.6.1]-paracyclophane and β-cyclodextrin
The inclusion complexations of paracyclophane (CP44) and β-cyclodextrin (β-CD) with several anilinonaphthalene sulfonic acids (ANSs) have been characterized via the enhancement of fluorescence spectra upon inclusion. β-CD and CP44 formed 1:1 inclusion complexes with ANSs, and the high stability of inclusion complexes of the latter was demonstrated. The thermodynamic parameters observed from the temperature dependence of the inclusion constants (van’t Hoff analysis) showed that CP44 inclusion complexations with ANSs are enthalpy-driven. Furthermore, the structure of the inclusion complexes was discussed based on 1H- and 2D ROESY-NMR measurements. It was found that CP44 encapsulates the naphthalene moiety of ANSs. On the other hand, differences in the structures of the β-CD inclusion complexes were observed for the 4-OH-substituted ANS. The molecular recognition for the inclusion of β-CD was found to be sensitive compared with that of CP44. In addition, the local polarity inside the CP44 and β-CD cavities was evaluated using ANSs as the fluorescence probe. Based on these results, we have suggested that the local polarity of ANSs in the hydrophobic cavities of CP44 and β-CD plays an important role in quantum yield enhancement upon inclusion.
Spectroscopic determination of pressure-induced shifts in inclusion complexation equilibria
The effect of modest hydrostatic pressure (c ranging from clearly pressure dependent (-14%) to pressure independent over 338 bar. Additional solvation perturbations are observed in the pressure dependence of the quantum efficiency for both complexes (-7.3% and -9.4%). Thus, pressure-induced perturbation in the fluorescence properties of the complex need not be accompanied by simultaneous changes in the complexation equilibrium. Finally, these pressure-induced changes in complexation selectivity are important for all measurements conducted under variable pressure conditions, including liquid chromatography and process monitoring.
Evans, Christine E.
p. 2136 - 2142
(2007/10/03)
Thermodynamic Study on the Effects of β-Cyclodextrin Inclusion with Anilinonaphthalenesulfonates
Thermodynamic parameters and stoichiometries for the binding of anilinonaphthalenesulfonates to β-cyclodextrin are obtained from steady-state fluorescence intensity and anisotropy measurements.Specifically, formation constant, enthalpy, and entropy values are obtained for complexes of β-cyclodextrin with eight different substrate molecules at five different temperatures and six different pH values, and their associated errors are given.We propose an explanation of the relative magnitudes of the values obtained with regard to the geometry of the substrate and the importance of the various noncovalent interactions responsible for the complexation.
Catena, Gino C.,Bright, Frank V.
p. 905 - 909
(2007/10/02)
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