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Oxazinoindolines as Fluorescent H+ Turn-On Chromoionophores For Optical and Electrochemical Ion Sensors

Published in Analytical Chemistry. 2013, vol. 85, no. 15, p. 7434-7440
Abstract We propose here a new class of fluorescent H<sup>+</sup> turn-on oxazinoindoline (Ox) dyes as chromoionophores suitable for the development of polymeric ion-selective membranes. Through rational design, oxazinoindolines with varying basicities and tunable absorption bands that extend to the near-infrared region were prepared. The basicities of the compounds were evaluated by potentiometry and fluorescence spectroscopy. By comparing the potentiometric lower detection limit with chromoionophore I (pK<sub>a</sub> = 14.80 ± 0.03 in PVC-NPOE), pK<sub>a</sub> values were determined for Ox Y, Ox R, and Ox B to be 9.80 ± 0.03, 12.85 ± 0.03, and 12.95 ± 0.03, respectively. Unlike conventional pH indicators that involve only a protonated and deprotonated form, a third species, arising from the thermal isomerization of the Ox compounds in polar solvents, may influence the overall protonation equilibrium. Interestingly, this results in an apparent pK<sub>a</sub> increase in the fluorescence mode when more polar PVC-NPOE membranes were utilized. The isomerization is suppressed in nonpolar PVC-DOS membranes. Na<sup>+</sup>-selective optical sensors were successfully prepared using the Ox dyes as an early application of the compounds in ion-selective optical sensors. The compounds were also successfully evaluated in a dynamic electrochemistry (chronopotentiometry) sensing mode for the detection of total alkalinity.
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Research group Groupe Bakker
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XIE, Xiaojiang, CRESPO PARAVANO, Gaston Adrian, BAKKER, Eric. Oxazinoindolines as Fluorescent H+ Turn-On Chromoionophores For Optical and Electrochemical Ion Sensors. In: Analytical Chemistry, 2013, vol. 85, n° 15, p. 7434-7440. doi: 10.1021/ac401367b https://archive-ouverte.unige.ch/unige:31510

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Deposited on : 2013-12-02

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