Towards understanding of stepwise acid-base dissociation in systems inclined to tautomerism: Nitro derivatives of fluorescein in dimethyl sulfoxide

Mchedlov-Petrossyan, N.O.; Cheipesh, T.A.; Moskaeva, E.G.; Shekhovtsov, S.V.; Ostrovskyi, K.I.

doi:10.1016/j.molliq.2023.122540

Cited by 2 publications

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“…In future, we plan to study the acid-base and tautomeric equilibria of compounds 2 and 5 in solution, thereby continuing the systematic study of the nitro-and amino derivatives of fluorescein [27,36]. The thermodynamic pK a values for compounds 6 and 7 in DMSO at 25 • C, have already been determined as 10.46 ± 0.07 and 11.12 ± 0.07, respectively [39].…”

Section: Atommentioning

confidence: 99%

“…As it was mentioned in Section 1, these values are probably somewhat overestimated because for fluorescein, Moir reports a value of 493.5 nm. The samples of the 4nitrofluorescein and 5 -nitrofluorescein, used for our measurements, were prepared and identified in a standard way; their characterization and acid-base properties were published recently [36].…”

Section: Atommentioning

confidence: 99%

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3′-Nitro- and 3′-Aminofluoresceins: Appearance of Previously Missing Dyes

Shekhovtsov,

Omelchenko,

Shishkina

et al. 2023

Colorants

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Contrary to the 4′- and 5′-nitro- and aminofluoresceins, the corresponding 3′-derivatives are practically unexplored. In this paper, we describe the synthesis and spectral properties of 3′-nitrofluorescein and 3′-aminofluorescein, as well as their methyl esters. Among other methods, X-ray analysis, 13C NMR spectroscopy, and ESI mass spectrometry made it possible to establish the molecular structure of the target compounds as well as intermediates and by-products. Some unexpected products, though in small amounts, were revealed within the course of study. Whereas the fluorescence of the double-charged R2− ion of 3′-nitrofluorescein in both aqueous and organic solvents is weak, the R2− anion of 3′-aminofluorescein in a non-hydrogen bonding donor solvent, but not in water, exhibits intensive fluorescence, analogous to the case of 4′- and 5′-aminofluoresceins. Interestingly, the λmax values in water of the R2− ions bearing an NO2 group in the 3′- and 6′-positions are 7 to 10 nm higher than those of the 4′- and 5′-nitro derivatives. The difference was also observed in dimethyl sulfoxide. This correlates with the angles between the xanthene and phthalic planes of the dyes. The dye 3′-aminofluorescein could be used as a fluorescent indicator sensitive to hydrogen bonding ability of the solvent. It could also serve as a platform for synthesizing fluorescent molecular probes for biochemical research, analogous to the very popular application of 4′- and 5′-amino derivatives.

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Section: Atommentioning

confidence: 99%

Section: Atommentioning

confidence: 99%