NMR Investigations of the Interaction Between the Azo-Dye Sunset Yellow and Fluorophenol

Abstract

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Influence of Structural Isomerism and Fluorine Atom Substitution on the Self-Association of Naphthoic Acid

“…27,29 This model has been extensively reviewed by Martin 30 and only the salient points will be reproduced here.…”

“…27,29,30 7 Data analysis was performed by implementing the models described above using the open source SciPy library 34 of the Python programming language. Error estimation in the fitted parameters was performed using Monte Carlo methods.…”

“…This trend in decreasing diffusion coefficient is consistent with the formation of larger assemblies at higher concentration and is similar to trends seen with other self-associating aromatic systems, such as sunset yellow. [27][28][29] While it is possible that there is an increase in solvent viscosity with increasing naphthoic acid concentration this is unlikely to be responsible for the observed changes in chemical shift. Any change in sample viscosity would typically result in a change in the spectral line width.…”

“…[21][22][23][24] A number of physical techniques can provide information on aggregation processes such as optical absorption, 3 x-ray scattering 3,13,25,26 and nuclear magnetic resonance (NMR) spectroscopy. 10,12,[26][27][28] In general, absorption and scattering based experiments provide information on the bulk properties of a sample, e.g. average aggregate sizes etc.…”

“…More recently, we have explored the interaction of a structurally similar small probe molecule with sunset yellow. In these studies two different motifs were used: fluorophenols 27 and an 4 isomer of fluoronaphthoic acid, 29 both of which were chosen so as to mimic part of the sunset yellow structure. The inclusion of the fluorine atom provided a unique NMR-active reporter nucleus with which to track the interaction of the small molecule with the sunset yellow assemblies.…”