Excited-State Proton Transfer of Fluorescein Anion as an Ionic Liquid Component

Rodrigues, Catarina A. B.; Graça, Cátia A.L.; Maçôas, Ermelinda; Fedorov, Alexander; Afonso, Carlos A. M.; Martinho, J. M. G.

doi:10.1021/jp408616r

Cited by 12 publications

(7 citation statements)

References 35 publications

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“…The aforementioned methodology can be applied to the incipient field of fluorescent ionic liquids bearing cationic or anionic chromophores. 23 Figure 8 shows the emission of tris(1butyl-3-methylimidazolium) 8-hydroxypyrene-1,3,6-trisulfonate (BMIM 3 HPTS). 24 When diluted with the slightly fluorescing ionic liquid 1-butyl-3-methylimidazolium chloride (BMIMCl), a very strong blue fluorescence is observed for excitation with 405 nm, arising from HPTS anions.…”

Section: Transparent Mediamentioning

confidence: 99%

Photophysics at Unusually High Dye Concentrations

et al. 2018

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Conspectus The study of the interaction of light with systems at high dye concentrations implies a great challenge because several factors, such as emission reabsorption, dye aggregation, and energy trapping, hinder rationalization and interpretation of the involved photophysical processes. Space constraints induce dye interaction even in the absence of ground state stabilization of dimers and oligomers. At distances on the order of 1 nm, statistical energy traps are usually observed. At longer distances, excited state energy transfer takes place. Most of these factors do not result in ground state spectroscopic changes. Rather, fluorescence phenomena such as inner filter effects, concentration-dependent Stokes’ shifts, and changes in quantum yields and decay times are evidenced. Photophysical studies are commonly carried out at high dilution, to minimize dye–dye interactions and emission reabsorption, and in the absence of light scattering. Under these conditions, the physical description of the system becomes rather simple. Fluorescence and triplet quantum yields become molecular properties and can be easily related to ratios of rate constants. However, many systems containing dyes able to fulfill specific functions, whether man-made or biological, are far from being dilute and scattering-free. The photosynthetic apparatus is a paradigmatic example. It is clear that isolation of components allows gathering relevant information about complex systems. However, knowledge of the photophysical behavior in the unaltered environment is essential in most cases. Complexity generally increases when light scattering is present. Despite that, our experience shows that light scattering, when correctly handled, may even simplify the task of unraveling molecular parameters. We show that methods and models aiming at the determination and interpretation of fluorescence and triplet quantum yields as well as energy transfer efficiencies can be developed on the basis of simple light-scattering theories. Photophysical studies were extended to thin films and layer-by-layer assemblies. Procedures are presented for the evaluation of fluorescence reabsorption in concentrated fluid solutions up to the molar level, which are being applied to ionic liquids, in which the emitting species are the bulk ions. Fluorescence reabsorption models proved to be useful in the interpretation of the photophysics of living organisms such as plant leaves and fruits. These new tools allowed the assessment of chlorophyll fluorescence at the chloroplast, leaf and canopy levels, with implications in remote sensing and the development of nondestructive optical methods.

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Section: Transparent Mediamentioning

confidence: 99%

Photophysics at Unusually High Dye Concentrations

et al. 2018

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“…The dianionic form is the most luminescent one, and its contribution to the dye total emission exceeds the others. A shoulder on the edge of the main peak (emission of the dianionic form) may be observed, indicating the presence of the monoanionic form [6]. Indeed, the monoanionic form also exhibits luminescent properties but its emission is much weaker, and the global emission spectra are blue-shifted with a broadening of the emission band compared to that of the dianionic form.…”

Section: Introductionmentioning

confidence: 97%

Revisiting fluorescein and layered double hydroxide using a synergistic approach: A complete optical study

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Leroux

Thérias

et al. 2019

Journal of Luminescence

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The luminescence of Fluorescein, an inexpensive dye, ought to be interesting for lighting application devices such as commercial LEDs. However, the molecule suffers from severe instability, making it inappropriate for such applications. As previously studied, fluorescein molecules may be hosted in a layered double hydroxide (LDH), and the role of such an inorganic material in stabilizing the dye has been underlined. However, a deep understanding of the resulting optical properties is still required. Using extremely small amounts of fluorescein, it is demonstrated here that Zn 2 Al cation-based LDH tethering acts as a «solid solvent» for the dye, enabling its luminescence even in powder form, whereas fluorescein molecules on their own emit no luminescence at all in the solid state. However, aggregations of the dye occur in the interlamellar space, leading to non-radiative emission. Emission and excitation spectra, as well as fluorescence decays, are studied to explain the difference between the hybrid LDH-Fluorescein material and an aqueous solution of fluorescein. Additionally, LDH platelets are found to help the dispersion of the intercalated fluorescein in silicone to obtain a homogeneous composite film, which exhibits luminescent properties. Finally, an accelerated photoaging study demonstrates that the LDH-fluorescein filler has a pro-degradant effect on polymer aging under UV radiation.

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“…36 Besides studies of fluorescein behavior in room-temperature ionic liquids (RTILs), 37 the ions of fluorescein dyes are already used in the preparation of a new kind of RTIL as an anionic component. 38,39 In turn, the medium effects may seriously influence the spectral and protolytic properties of the dyes. Fluorescein and its halogen and nitro derivatives are diprotic acids, hereafter designated as H 2 R. They ionize in solutions to form anions, HR − and R 2− V H R HR H…”

Section: Introductionmentioning

confidence: 99%

“…For instance, the photophysical and spectral properties were studied for hydroxyxanthenes fixed in surfactant micelles and chitosan-based polyelectrolytes; , the singlet oxygen delivery by Rose Bengal B was studied in mesostructured silica nanoparticles . Besides studies of fluorescein behavior in room-temperature ionic liquids (RTILs), the ions of fluorescein dyes are already used in the preparation of a new kind of RTIL as an anionic component. , In turn, the medium effects may seriously influence the spectral and protolytic properties of the dyes.…”

Section: Introductionmentioning

confidence: 99%

Aminofluoresceins Versus Fluorescein: Ascertained New Unusual Features of Tautomerism and Dissociation of Hydroxyxanthene Dyes in Solution

et al. 2019

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Within the course of this spectroscopic research, we revealed novel features of the protolytic behavior, which extend the knowledge of the chemistry of xanthene dyes and rationalize the utilization of these compounds. In addition to the well-known tautomerism of the molecular form, H 2 R, of fluorescein dyes, new aspects of tautomeric transformation of anions are disclosed. First, for the dyes bearing the substituents in the phthalic acid residue, 4′-and 5′-aminofluoresceins and 4′-fluorescein isothiocyanate, the monoanion HR − exists in non-hydrogen-bond donor solvents not only as a tautomer with the ionized carboxylic and nonionized OH group but also as a "phenolate" ion with a nonionized COOH group. Such state of HR − ions is typical for dyes bearing halogen atoms or NO 2 groups in the xanthene moiety but was not observed until now in the case of substitution in the phthalic residue. Second, the possibility of the existence of the HR − species in DMSO in the form of colorless lactone is deduced for the 5′-aminofluorescein using the visible and infrared spectra. This results in a dramatic difference in medium effects. For instance, whereas for fluorescein in DMSO, the inversion of the stepwise ionization constants takes place and the K a1 /K a2 value equals 0.08, the same ratio for 5′-aminofluorescein is as high as ∼800. In addition, the pK a values of sulfonefluorescein, erythrosin, methyl ether of fluorescein, and phenol red were obtained to verify the acidity scale in DMSO and to support the detailed scheme of protolytic equilibria of fluorescein dyes.

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Excited-State Proton Transfer of Fluorescein Anion as an Ionic Liquid Component

Cited by 12 publications

References 35 publications

Photophysics at Unusually High Dye Concentrations

Photophysics at Unusually High Dye Concentrations

Revisiting fluorescein and layered double hydroxide using a synergistic approach: A complete optical study

Aminofluoresceins Versus Fluorescein: Ascertained New Unusual Features of Tautomerism and Dissociation of Hydroxyxanthene Dyes in Solution

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