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Water-Soluble Colorimetric Amino[bis(ethanesulfonate)] Azobenzene pH Indicators: A UV–Vis Absorption, DFT, and 1H–15N NMR Spectroscopy Study
- Source :
- ACS Omega, Vol 2, Iss 9, Pp 6159-6166 (2017), ACS Omega
- Publication Year :
- 2017
- Publisher :
- American Chemical Society (ACS), 2017.
-
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.<br />peer-reviewed
- Subjects :
- General Chemical Engineering
Metal ions in aqueous solution
Protonation
010402 general chemistry
Photochemistry
01 natural sciences
Medicinal chemistry
Article
Acid dissociation constant
lcsh:Chemistry
chemistry.chemical_compound
Charge transfer
pH indicator
010405 organic chemistry
Chemistry
Molecules -- Research
General Chemistry
Nuclear magnetic resonance spectroscopy
Binding constant
Indicators and test-papers
3. Good health
0104 chemical sciences
lcsh:QD1-999
Azobenzene
Selectivity
Analytical chemistry
Subjects
Details
- ISSN :
- 24701343
- Volume :
- 2
- Database :
- OpenAIRE
- Journal :
- ACS Omega
- Accession number :
- edsair.doi.dedup.....1ea3547277b08f734ea1cc9b8a986b2d