Acid-base dissociation and tautomerism of two aminofluorescein dyes in solution

Mchedlov‐Petrossyan, Nikolay O.; Cheipesh, Tatyana A.; Vodolazkaya, Natalya A.

doi:10.1016/j.molliq.2016.10.121

Cited by 13 publications

(40 citation statements)

References 35 publications

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“…The fluorescence of BBDMAF , which was expected to increase at pH < 3 due to further suppression of PET, decreased due to the formation of the ammonium xanthene form, which shows very low absorption. In addition, the absorbance of BBDMAF increased in the pH region where the cationic xanthene form (dicationic form) prevailed because its absorption is known to be greater than that of the ammonium xanthene form [ 9 , 19 , 20 ]. Accordingly, we measured the absorption and emission spectra of BDMAF and BBDMAF at pH −0.30, −0.56, and −0.94 ( Figure S4 ).…”

Section: Resultsmentioning

confidence: 99%

5-Bromo-4′,5′-bis(dimethylamino)fluorescein: Synthesis and Photophysical Studies

et al. 2018

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In this study, three new fluorescein derivatives—5-bromo-4′,5′-dinitrofluorescein (BDNF), 5-bromo-4′,5′-diaminofluorescein (BDAF), and 5-bromo-4′,5′-bis(dimethylamino)fluorescein (BBDMAF)—were synthesized and their pH-dependent protolytic equilibria were investigated. In particular, BBDMAF exhibited pH-dependent fluorescence, showing strong emission only at pH 3–6. BBDMAF bears a bromine moiety and thus, can be used in various cross-coupling reactions to prepare derivatives and take advantage of its unique emission properties. To confirm this, the Suzuki and Sonogashira reactions of BBDMAF with phenylboronic acid and phenylacetylene, respectively, were performed, and the desired products were successfully obtained.

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Section: Resultsmentioning

confidence: 99%

5-Bromo-4′,5′-bis(dimethylamino)fluorescein: Synthesis and Photophysical Studies

et al. 2018

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“…For BDMAF , the molar absorptivities of the protolytic species, except for the cationic form, did not differ greatly, with the greatest increase in fluorescence occurring between p K a1 (3.37) and p K a2 (5.83)‐the range in which most of the BDMAF species existed in neutral form. The neutral form of fluorescein in aqueous solution exists in zwitterionic, quinoidal, and lactonic forms in a ratio of 0.22:0.11:0.67 (Scheme S1) . Accordingly, we can suggest the protolytic equilibria of BDMAF (Scheme S2).…”

Section: Methodsmentioning

confidence: 90%

“…Numerous literature data reveal that the absorption bands of the cationic xanthene, neutral quinoid, and quinone‐phenolate forms of fluorescein are quite different (Figure S6) . Indeed, a broad single absorption band is typically observed for the cationic xanthene, a broad triple band (sometimes short‐wavelength shoulders are overlapped) for the neutral quinoid, and a broad double‐band for the negative quinone‐phenolate.…”

Section: Methodsmentioning

confidence: 99%

4′,5′‐Bis(dimethylamino)fluorescein Exhibits pH‐Dependent Emission Behavior Distinct From That of Fluorescein

2017

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4',5'-Diaminofluoresein (DAF)a nd 4',5'-bis(dimethylamino)fluorescein (BDMAF)h ave been synthesized and their pH-dependent photophysical properties and protolytic equilibria investigated. Although the parentf luorescein exhibits decreased emission upon decreasing pH, DAF displayed quenched emission at all pH values;s urprisingly, BDMAF exhibiteds trong fluorescenceo nly at pH 3-6, with its emission almost completely quenched under strongly acidic, neutral, and basic conditions. Fluorescein and its derivatives are used widely in modernb iochemical, biological,m edicinal, and photochemical research because of their excellent photophysical properties (Figure S1).[1] The light absorption and fluorescencep roperties of fluoresceind epend on the pH of the medium-the result of its containing acidic functional groups.[2] The protolytic equilibrium of fluorescein involves four species (cation, neutral, monoanion, dianion), with values of pK a of approximately 2, 4, and 6 (Scheme S1). Although the monoanionic and dianionic forms are the main ground-state species under biologically relevant conditions, their photophysical properties are quite distinct. For example, the absorbance of the monoanionic form is weak and its maximum is blue-shifted relative to that of the dianionic form. More importantly,t he fluorescencei ntensity of the monoanionic form is significantly lower than that of the dianionic form. Therefore, the pH of the mediumi sa ni mportant factor when studying systemsc ontaining fluorescein because it will exhibit weak emission intensity in aw eakly acidic environment. Because the value of pK a of the phenolic unit involved in the equilibrium between the monoanionic and dianionic forms in aqueous solutioni sa pproximately 6, close to the physiological pH, fluorescein derivatives containing electron-withdrawing groups (e.g.,halogen atoms on the xanthene ring) have been prepared previouslyi na ttempts to increase the acidity of the phenolic group.[3] Nevertheless, these compounds, like fluorescein,h ave exhibited pH-sensitivity problems of their own, with the fluorescencee missiond ecreasing upon decreasing the pH.Various intracellularo rganellesm aintain as teady pH, typically in the range from 5.0 (lysosomes)t o8 .0 (mitochondria).[4] In particular, there is increasing interesti nd eveloping efficient probesf or detecting the acidic pH induced by the active metabolism of cancer cells.[5] Therefore, we became interested in preparing fluoresceind erivativesd isplaying good fluorescence properties under acidic pH. We found recently that the introductiono fa mino or N,N-dimethylamino moieties on the fluorene ring led to significantly enhanced emissionsu nder acidic pH, relative to those under neutralo rb asic pH.[6] Some examples of fluoresceind erivatives having amino groups on the benzoica cid ring, rather than on the xanthene structure, have been reported, but their fluorescencei squenched at all values of pH. [7] 4',5'-Dimethyl-2',7'-diaminofluorescein is, to the best of our knowledge, the only exampl...

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“…Accordingly, new works appear on the protolytic and spectral properties of both previously known [28][29][30][31][32] and new [25,[33][34][35] or previously little studied [36][37][38][39][40][41][42] fluorescein compounds, including data analysis in the gas phase [43][44][45].…”

Section: Introductionmentioning

confidence: 99%

“…For the majority of the dyes the calculations can be simplified due to negligible equilibrium concentrations of H3R + ions at working pH values. The data were processed by using the CLINP program [15,39,40,56]. Normally, 15 working solutions with various pH values and 20 analytical wave lengths were used for determining the a a pK values of "overlapping" equilibria, Equations (4) and (5).…”

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confidence: 99%

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

Mchedlov‐Petrossyan

Vodolazkaya

2021

Liquids

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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.

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Acid-base dissociation and tautomerism of two aminofluorescein dyes in solution

Cited by 13 publications

References 35 publications

5-Bromo-4′,5′-bis(dimethylamino)fluorescein: Synthesis and Photophysical Studies

5-Bromo-4′,5′-bis(dimethylamino)fluorescein: Synthesis and Photophysical Studies

4′,5′‐Bis(dimethylamino)fluorescein Exhibits pH‐Dependent Emission Behavior Distinct From That of Fluorescein

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

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