Please use this identifier to cite or link to this item: https://www.um.edu.mt/library/oar/handle/123456789/70761
Title: Water-soluble colorimetric amino[bis(ethanesulfonate)] azobenzene pH indicators : a UV-vis absorption, DFT, and 1H-15N NMR spectroscopy study
Authors: Cardona, Maria A.
Makuc, Damjan
Szaciłowski, Konrad
Plavec, Janez
Magri, David C.
Keywords: Charge transfer
Molecules -- Research
Indicators and test-papers
Analytical chemistry
Issue Date: 2017
Publisher: American Chemical Society
Citation: Cardona, M. A., Makuc, D., Szaciłowski, K., Plavec, J., & Magri, D. C. (2017). Water-soluble colorimetric amino[bis(ethanesulfonate)] azobenzene pH indicators : a UV-vis absorption, DFT, and 1H-15N NMR spectroscopy study. ACS Omega, 2017(2), 6159-6166.
Abstract: Water-soluble azobenzene derivatives containing amino[bis(ethanesulfonate)] groups are demonstrated as colorful pH indicators in water and on filter paper. Vibrant color changes were observed from yellow/orange to pink between pH 1 and 4, which are attributed to an intramolecular charge-transfer mechanism. The pKas of the indicators range from 2.1 to 2.6. 1H/1H–15N NMR studies in deuterium oxide reveal that the protonation of the azobenzene pH indicators occurs predominantly at the β-azo nitrogen atom, in agreement with the density functional theory calculations. Excellent selectivity for protons was confirmed in water over common biologically relevant metal ions. Studies in methanol, however, indicate that the pH indicator with a methoxy group ortho to the amino[bis(ethanesulfonate)] group facilitates the selective coordination of Cu2+ with a binding constant pβCu2+ of 4.6 ± 0.1. The indicators complement the existing library of azobenzene indicator dyes and may be useful for measuring the environmental pH at higher proton concentrations.
URI: https://www.um.edu.mt/library/oar/handle/123456789/70761
Appears in Collections:Scholarly Works - FacSciChe



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