3,3′‐Dinitrophenolsulphonephthalein: an acid–base indicator dye with unusual properties

2021

Coloration Technology

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The rupture of the pyran ring of fluorescein and rhodamine dyes is well documented. [1][2][3][4][5] For the mother compound fluorescein (1), the process occurs in extremely alkaline media. According to Orndorff et al, 3 in cold 33% aqueous potassium hydroxide (KOH) first the absorption band at 496 nm is only observed, whereas a new band with λ max = 583 nm (2) appears only after 5-10 weeks (Scheme 1). (It should be taken into account that, according to Lewis, these λ max values are 10-20 nm overestimated. 6 ) However, in hot aqueous KOH of the same concentration the last-named band appears immediately.Accordingly, the intensity of the first band decreases, but over time the solution is discoloured owing to formation of carbinol 3. 3 The latter is a result of nucleophilic attack of the hydroxide (HO -) on the nodal carbon atom. Even earlier, Meyer and Fischer observed the spectrum of the "violet fluorescein" after boiling fluorescein with sodium hydroxide (NaOH). 2 Analogous reactions were described for rhodamine dyes; further research is summarised in the corresponding review. 1 For eosin, the opening of the heterocycle occurs at markedly lower alkali concentration. 4 Contrary to halogen derivatives of triphenylmethine and hydroxyxanthene dyes, the nitro derivatives are largely ignored. However, as early as 1900-1902 it was already known that in alkaline solutions, 2,7-dibromo-4,5-dinitrofluorescein and 4,5-dinitrofluorescein gradually turned from yellow to deep blue, and the last dye becomes colourless after action of hot alkali over time. 7,8 El'tsov et al 9 proved the results for the last-named dye spectroscopically. In a 0.1 mol/L sodium hydrogen carbonate (NaHCO 3 ) aqueous solution, the initial dye exists in the form of a double-charged anion (λ max = 482 nm), while at pH > 11 the pyran cycle opens; λ max = 580 nm. The

Section: 5-dinitrosulfonefluoresceinmentioning

confidence: 49%

Section: Methodsmentioning

confidence: 99%

4,5‐Dinitrosulfonefluorescein and related dyes: Kinetics of reversible rupture of the pyran ring and their interaction with lysozyme

Kriklya

Gromovoy

2021

Coloration Technology

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“…Naturally, the visual absorption bands of anions 17 and 18 in aqueous alkali are similar to those of the R 2− anions of 3,3′‐dinitrosulphonephthalein (nitrophenol violet) and 3,3′,5,5′‐tetranitrosulphonephthalein (nitrophenol crimson), at λ = 568 nm and 558 nm , respectively. Moreover, quantitative studies demonstrated that the nucleophilic attack of HO − , which results in carbinol formation, occurs much more quickly in the case of nitrophenol crimson .…”

Section: Resultsmentioning

confidence: 71%

“…The current article aims to further examine TNF, thus enhancing previous research and simultaneously extending the research into the series of nitro‐substituted triphenylmethine and xanthenes dyes . In particular, the transformations of TNF in highly basic media were examined using electrospray spectroscopy and X‐ray analysis.…”

Section: Introductionmentioning

confidence: 99%

The molecular structure of anionic species of 2,4,5,7‐tetranitrofluorescein as studied by electrospray ionisation, nuclear magnetic resonance and X‐ray techniques

Steinbach

Vodolazkaya

et al. 2018

Coloration Technology

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Among the fluorescein dyes, the behaviour of their nitro derivatives in solution is most unusual, and yet at the same time rarely studied. In this study, their 13 C nuclear magnetic resonance and electrospray spectra are reported, which confirm, in concert with their ultraviolet-visible spectra, the molecular structures of the neutral and ionic species of 2,4,5,7-tetranitrofluorescein observed in different solvents and at various pH values. A peculiar property of this dye consists in its lactonisation of the double-charged anion, contrary to the wellknown coloured and fluorescent dianions of fluorescein, eosin, etc. Also, this dianion-lactone exhibits high ability for opening the pyran ring. This cleavage takes place at much lower pH values as compared with those for fluorescein and its halogen derivatives. The ruptured species can be formed as either lactone or carbinol; the latter appears as a result of the nucleophilic attack of a HO À on the central carbon atom. The corresponding molecular structures are identified via the electrospray method and X-ray analysis. The behaviour of some other nitrofluoresceins in alkaline media is also considered. Coloration TechnologySociety of Dyers and Colourists † Just now, an article "Syntheses of novel acid-base indicators by nitration of phenolphthalein and fluorescein" by Y. Negishi,

“…the same effect as four Br atoms. Analogous conclusion may be made when comparing the pK a a2 values of 3,3 ,5,5 -tetrabromo sulfonephthalein (indicator bromophenol blue) and 3,3 -dinitro-sulfonephthalein (nitrophenol violet) both in water and dimethyl sulfoxide [77]. Therefore, the dramatic increase in the pK a a1 and decrease in the (pK a a2 − pK a a1 ) of 4,5-dinitro derivatives ( As result, the negative contribution of the term log α H 2 Q is substantial.…”

Section: Dependence Of the Ratio Of The Values Of The Stepwise Ionizamentioning

confidence: 60%

Protolytic Equilibria in Organized Solutions: Ionization and Tautomerism of Fluorescein Dyes and Related Indicators in Cetyltrimethylammonium Chloride Micellar Solutions at High Ionic Strength of the Bulk Phase

Vodolazkaya

2021

Liquids

Ionic equilibrium of 22 hydroxyxanthenes, including halogen and nitro derivatives of fluorescein, and their thio- and aza analogues, were studied spectrophotometrically in micellar solutions of cetyltrimethylammonium chloride at ionic strength of the bulk phase 4.0 M KCl. This micellar pseudophase is characterized by the electrostatic surface potential of +(15–16) mV and the ETN value of 0.623. In the case of dyes bearing the COOH group, colorless lactone is the predominant tautomer of the molecular form H2R. A new classification of fluoresceins is developed. The dyes were divided into four groups based on the nature of tautomerism of the anions. In the case of the fluorescein type, the monoanions HR− exist predominantly as “carboxylate” tautomers, with ionized carboxylic and non–ionized hydroxylic group. For the dyes of the eosin type, the situation is opposite, while for the intervening type of compounds, the concentrations of the two tautomers are comparable. Dyes capable of forming lactone anions HR− were classified as the fourth type. For some of them, even the dianion R2− exists as a lactone. The relationship between the stepwise ionization constants, Ka1/Ka2, varies from 1.3 to 1.07 × 105 and is determined by the state of tautomeric equilibrium of molecules and ions.