ChemInform Abstract: Radiationless Deactivation of the Excited Phototautomer Form and Molecular Structure of ESIPT Compounds

Дорошенко, А. О.; Posokhov, E. A.; Verezubova, A. A.; Ptyagina, L. M.; Skripkina, V. T.; Shershukov, V. M.

doi:10.1002/chin.200237298

Cited by 3 publications

(8 citation statements)

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“…Electronwithdrawing groups introduced in the protonated moiety, or electron-donating groups introduced in the deprotonated 25 moiety, facilitate therefore the TICT process, with concomitant enhancement of the radiationless deactivation and photoprotector efficiency. 28,29,35,49,53 On the contrary, electron-withdrawing substituents introduced in the deprotonated moieties of several ESIPT molecules decrease the rate of the radiationless deactivation and increase consequently their fluorescence quantum yields. 53 Various authors have stressed the relevance of this knowledge for the design of new ESIPT dyes useful as UV absorbers or fluorescent probes.…”

Section: Introductionmentioning

confidence: 99%

“…28,29,35,49,53 On the contrary, electron-withdrawing substituents introduced in the deprotonated moieties of several ESIPT molecules decrease the rate of the radiationless deactivation and increase consequently their fluorescence quantum yields. 53 Various authors have stressed the relevance of this knowledge for the design of new ESIPT dyes useful as UV absorbers or fluorescent probes. 28,53 As mentioned above, a key factor that modulates the efficiency of the TICT process of the proton-transferred phototautomer is the strength of the electron donor and electron acceptor.…”

Section: Introductionmentioning

confidence: 99%

“…53 Various authors have stressed the relevance of this knowledge for the design of new ESIPT dyes useful as UV absorbers or fluorescent probes. 28,53 As mentioned above, a key factor that modulates the efficiency of the TICT process of the proton-transferred phototautomer is the strength of the electron donor and electron acceptor. For example, no experimental evidence for TICT deactivation was found for the phototautomer of 2-(2'hydroxyphenyl)benzimidazole (HBI), 35 but its derivatives bearing a better electron donor (an amino or dialkylamino group at C4') were found to undergo a fast radiationless deactivation, which was interpreted as a coupled ESIPT-TICT process.…”

Section: Introductionmentioning

confidence: 99%

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Fluorescence of methylated derivatives of hydroxyphenylimidazopyridine. Resolution of strongly overlapping spectra and a new ESIPT dye showing very efficient radiationless deactivation

Brenlla

Veiga

Rodríguez

et al. 2011

Photochem Photobiol Sci

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The ground- and excited-state behaviour of the isomeric species 2-(2'-methoxyphenyl)imidazo[4,5-b]pyridine (1-OMe) and 2-(2'-hydroxyphenyl)-4-methylimidazo[4,5-b]pyridine (1-NMe) in neutral and acid media has been studied by UV-vis absorption spectroscopy, steady-state and time-resolved fluorescence spectroscopy. The new dye 1-NMe is non-fluorescent in neutral media except in trifluoroethanol, where it shows a very weak fluorescence. 1-NMe also exhibits highly solvent-dependent fluorescence intensity in acidic media. We propose that the neutral species experiences a fast excited-state intramolecular proton transfer (ESIPT), relaxing afterwards by intramolecular twisting associated with internal charge transfer (TICT) and subsequent very fast internal conversion of the proton-transferred TICT structure. The behaviour of 1-NMe in acidic media is explained by the existence of a ground-state tautomeric equilibrium between species with intramolecular hydrogen bonds N-HOH and NHO. The first type of tautomers dissociates at the hydroxyl group in water and ethanol, but fluoresces in acetonitrile and trifluoroethanol due to the inability of these solvents to accept the proton. The second type of tautomers is non-emissive due to fast radiationless deactivation through an ESIPT-TICT process. The fluorescence of 1-OMe was investigated in neutral and acidic media, demonstrating the photobasic character of the pyridine nitrogen. A ground-state equilibrium between pyridinium and imidazolium cations was found for this species, showing overlapping absorption and fluorescence spectra. We devised a method to resolve the spectra by applying principal component global analysis to a series of excitation spectra taken at different emission wavelengths, which allowed estimation of the equilibrium constant between the cations.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Fluorescence of methylated derivatives of hydroxyphenylimidazopyridine. Resolution of strongly overlapping spectra and a new ESIPT dye showing very efficient radiationless deactivation

Brenlla

Veiga

Rodríguez

et al. 2011

Photochem Photobiol Sci

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“…The formation of LEPT structures via excited state intramolecular proton transfer has been investigated in hydrogen-bonded phenol-pyridines [51][52] and similar phenol-N-base dyads. [53][54][55][56][57][58][59][60][61][62][63][64][65] For molecules similar to the phenol-pyridine dyad, the excited diradical LEPT state can undergo ultrafast radiationless decay to the GS, 52,55,62 and the rates of this decay depend on the polarity of the solvent. The exact mechanism of this ultrafast radiationless decay in such phenol-base systems is not clear, but it has been proposed to occur through conjugation and π-electron delocalization in the phenol-pyridine dyad and/or conformational relaxation.…”

Section: Resultsmentioning

confidence: 99%

Substituent Effects on Photochemistry of Anthracene–Phenol–Pyridine Triads Revealed by Multireference Calculations

Sayfutyarova

Hammes‐Schiffer

2019

J. Am. Chem. Soc.

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Inverted region behavior for concerted proton-coupled electron transfer (PCET) was recently demonstrated for biomimetic anthracene-phenol-pyridine molecular triads. Photoexcitation of the anthracene to a locally excited state (LES) is followed by concerted electron transfer from the phenol to the anthracene and proton transfer from the phenol to the pyridine, forming a relatively long-lived charge separated state (CSS). The long-lived CSS and the inverted region behavior associated with the decay from the CSS to the ground state through charge recombination were experimentally observed only for triads with certain substituents on the anthracene and the pyridine. To explain this distinction, we computed the proton potential energy curves in four substituted triads using the complete active space self-consistent-field method and multireference perturbation theory, including solvent effects with a dielectric continuum model. The calculations revealed a local electron-proton transfer (LEPT) state, in which both the electron and proton transfer from the phenol to the pyridine. When the LEPT state is lower in energy than the CSS, it may provide an alternative pathway for fast decay from the LES to the ground state and thereby preclude detection of the CSS and the inverted region behavior. These calculations predict that substituents stabilizing negative charge on the pyridine and destabilizing negative charge on the anthracene will favor the LEPT pathway, while substituents with the reverse effects will favor the CSS pathway, which could exhibit inverted region behavior. These insights about the stabilization of energy-storing charge-separated states have implications for designing and controlling PCET reactions in artificial photosynthetic systems and other energy conversion processes.

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“…Probes 1 and 2 allow a simultaneous monitoring of several parameters of their microenvironment: the fluorescence spectrum of probe 1 is sensitive to the protondonor ability as well as the polarity and viscosity of the probe environment; the shape of the fluorescence spectrum of probe 2 depends on the proton-donor ability of the medium, and the fluorescence intensity of probe 2 depends on the viscosity of the medium [49][50][51].…”

Section: Resultsmentioning

confidence: 99%

Fluorescent probes sensitive to changes in the cholesterol-to-phospholipids molar ratio in human platelet membranes during atherosclerosis

Posokhov

2016

Methods Appl. Fluoresc.

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Environment-sensitive fluorescent probes were used for the spectroscopic visualization of pathological changes in human platelet membranes during cerebral atherosclerosis. It has been estimated that the ratiometric probes 2-(2'-hydroxyphenyl)-5-phenyl-1,3,4-oxadiazole and 2-phenyl-phenanthr[9,10]oxazole can detect changes in the cholesterol-to-phospholipids molar ratio in human platelet membranes during the disease.

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ChemInform Abstract: Radiationless Deactivation of the Excited Phototautomer Form and Molecular Structure of ESIPT Compounds

Cited by 3 publications

References 1 publication

Fluorescence of methylated derivatives of hydroxyphenylimidazopyridine. Resolution of strongly overlapping spectra and a new ESIPT dye showing very efficient radiationless deactivation

Fluorescence of methylated derivatives of hydroxyphenylimidazopyridine. Resolution of strongly overlapping spectra and a new ESIPT dye showing very efficient radiationless deactivation

Substituent Effects on Photochemistry of Anthracene–Phenol–Pyridine Triads Revealed by Multireference Calculations

Fluorescent probes sensitive to changes in the cholesterol-to-phospholipids molar ratio in human platelet membranes during atherosclerosis

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