Photoinduced intramolecular proton transfer as the mechanism of ultraviolet stabilizers: a reappraisal [Erratum to document cited in CA112(5):35179y]

Catalán, Javier; Fabero, Fernando; Guijarro, M.S.; Claramunt, R. M.; Maria, Maria Dolores Santa; Foces-Foces, Maria de la Concepcion; Cano, F. H.; Elguero, José; Sastre, R.

doi:10.1021/ja00010a087

Cited by 5 publications

(4 citation statements)

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“…UV absorbers with an intramolecular hydrogen bond (e.g., methyl salicylates, o-hydroxybenzophenones, 2-(2-hydroxyaryl)benzotriazoles, and 2-(2-hydroxyaryl)-1,3,5-triazines) are of great importance for the protection of polymers against photodegradation. − Numerous investigations have demonstrated that photoexcitation is followed by an excited-state intramolecular proton-transfer (ESIPT), in accordance with Förster's theory. , Subsequent, highly efficient radiationless deactivation processes ensure that this type of molecule is a good UV stabilizer.…”

Section: Introductionmentioning

confidence: 93%

“…The radiationless deactivation process thence is concluded to originate from the proton-transferred level S 1 ‘. , Barbara et al ,, have suggested a slow, large-amplitude torsional motion for the temperature-dependent radiationless deactivation of the S 1 ‘ fluorescence of, for example, 2-(2-hydroxy-5-methylphenyl)benzotriazole (Tinuvin P (TIN P), trade name of Ciba Specialty Chemicals, Inc., see Chart 1). Elsaesser and co-workers 37 have concluded from their femtosecond experiments that the highly anharmonic in-plane deformation mode at 470 cm -1 modulates the separation between proton donor and acceptor atom, and thus plays a key role in the proton-transfer reaction of TIN P. Several comprehensive reviews deal with proton transfer in the excited state. ,,, Catalán et al recently reported results for (2-hydroxyphenyl)pyrazoles; 22a, the authors question whether proton transfer in the excited state is a prerequisite for efficient radiationless deactivation and thus for the suitability of a given compound as UV absorber 22a…”

Section: Introductionmentioning

confidence: 99%

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Ultraviolet Absorbers of the 2-(2-Hydroxyaryl)-1,3,5-triazine Class and Their Methoxy Derivatives: Fluorescence Spectroscopy and X-ray Structure Analysis

et al. 1998

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A close to planar conformation is established for 2-(4-methoxyphenyl)-4,6-diphenyl-1,3,5-triazine (M-H-P) by crystal structure determination. For 2-(4-hexoxy-2-methoxyphenyl)-4,6-diphenyl-1,3,5-triazine (H-MeO-P), hydrophobic interaction between the long hexoxy groups enforces rotation of the dialkoxyphenyl ring at C6 and the C2 phenyl ring relative to the plane of the triazine ring. Time-resolved fluorescence measurements demonstrate the existence of a short-lived Franck-Condon (FC) and a longer-lived TICT (twisted intramolecular charge transfer) state, emitting at longer wavelengths, for the O-methyl derivative 2-(4-hexoxy-2-methoxyphenyl)-4,6-bis(2,4,6-trimethylphenyl)-1,3,5-triazine (H-MeO-Ms). The decay of the protontransferred (PT) fluorescence for crystalline powders of 2-(2-hydroxyphenyl)-4-(dimethylamino)-6-aryl-1,3,5triazines is shown, by the same method, to be retarded within the series phenyl f tolyl f xylyl, well in line with the gradation of quantum yields determined by steady-state methods. The high quantum yields of the PT fluorescence for triazines with only one 2-hydroxyaryl moiety on the triazine ring are reduced by 2 orders of magnitude each upon introduction of a second and a third aryl group. Most of the 2-hydroxyaryl-1,3,5triazines with additional aryl moieties at C4 and C6 show PT fluorescence, as long as the 2-hydroxyaryl and the triazine ring are more or less coplanar and the intramolecular hydrogen bond remains intact. In some cases, however, this fluorescence is very weak, or can be detected only in copolymers, in mixtures of the stabilizer with the polymer or in crystalline powders.

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Section: Introductionmentioning

confidence: 93%

Section: Introductionmentioning

confidence: 99%

Ultraviolet Absorbers of the 2-(2-Hydroxyaryl)-1,3,5-triazine Class and Their Methoxy Derivatives: Fluorescence Spectroscopy and X-ray Structure Analysis

et al. 1998

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“…[19] These studies also includes various applications of intramolecular proton transfer reactions as chemical lasers, [20] energy storage systems and information storage devices at a molecular level, [21] high-energy radiation detectors [22] and polymer stabilizers. [23,24] Many research groups have reported interesting biological applications of excited state proton transfer (ESPT). [25] It has been reported that certain aromatic compounds like naphthols, carbazoles undergo enhancement in the acidity in the excited state as compared to the ground state and hence behaves as photoacids and compounds like acridine undergo enhancement in the basicity in the excited state as compared to the ground state and hence behaves as a photobase.…”

Section: Introductionmentioning

confidence: 99%

“…These studies includes determination of pK a * values of aromatic compounds, study of proton‐induced quenching mechanism, dynamic analyses [14] by means of nanosecond time‐resolved spectroscopy with fluorimetry, and applications of intermolecular excited state proton transfer (ESPT) in technological applications in pH [15] and pOH [16] jump experiments, study of proton hydration dynamics [17,18] and photolithography [19] . These studies also includes various applications of intramolecular proton transfer reactions as chemical lasers, [20] energy storage systems and information storage devices at a molecular level, [21] high‐energy radiation detectors [22] and polymer stabilizers [23,24] . Many research groups have reported interesting biological applications of excited state proton transfer (ESPT) [25]…”

Section: Introductionmentioning

confidence: 99%

How to Control Excited‐State Prototropism of Photoacids via the Acidity of Ionic Liquids

Kasana,

Saloni,

Kumar

2024

ChemistrySelect

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To control presence of ionic species in excited state of a fluorophore is quite challenging task. Herein, we report the unusual excited‐state prototropism of an important photoacid carbazole dissolved in water in presence of small amount of added ionic liquids (ILs). We have observed that the excited state prototropic equillibria of carbazole dissolved in water can be affected by the presence of small amount of added ILs. More importantly, the excited‐state prototropism of carbazole can be controlled via the acidity of added ILs. More specifically, we found that the fluorescence emission from the neutral prototropic form of carbazole can be observed even under highly basic conditions (aqueous NaOH, pH 12.6) in presence of only small amount of any of the added ILs such as 1‐butyl‐3‐methyl imidazolium tetrafluoroborate ([bmim][BF4]), 1‐butyl‐1‐methylpyrrolidinium bis(trifluromethansulphonyl)imide ([bmpyrr][Tf2N]) and 1‐butyl‐3‐methyl imidazolium hexafluorophosphate ([bmim][PF6]). The observed fluorescence emission from the neutral form of carbazole can be attributed to excited state protonation of carbazole anion by taking proton from IL cation. In a true sense, the excited state carbazole does not transfer the proton; rather takes the proton from IL cation. The observed unusual excited state protonation of carbazole anion to neutral carbazole, in the excited state even in highly basic conditions can be attributed to the presence of acidic protons with the IL cations. Herein, we reports quite unusual results where the IL assisted excited state protonation of carbazole anion occured in an exclusive manner in which proton from the IL cation exclusively protonate carbazole anion surrounded by highly alkaline media (water, pH 12.6). ILs acidity controlled excited‐state properties of important photoacids can have a wide range of chemical and biological applications and the observed results can play important roles in chemical technology to control prototropic equillibra with the help of ILs for some specific application. These observations can open new windows to attract more applications for these alternative solvent media to applications in pH and pOH jump experiments, effective photo protecting agents and chemical lasers.

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Excited-state proton transfer reactions I. Fundamentals and intermolecular reactions

Arnaut

Formosinho

1993

Journal of Photochemistry and Photobiology A: Chemistry

538

159

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Photoinduced intramolecular proton transfer as the mechanism of ultraviolet stabilizers: a reappraisal [Erratum to document cited in CA112(5):35179y]

Cited by 5 publications

References 0 publications

Ultraviolet Absorbers of the 2-(2-Hydroxyaryl)-1,3,5-triazine Class and Their Methoxy Derivatives: Fluorescence Spectroscopy and X-ray Structure Analysis

Ultraviolet Absorbers of the 2-(2-Hydroxyaryl)-1,3,5-triazine Class and Their Methoxy Derivatives: Fluorescence Spectroscopy and X-ray Structure Analysis

How to Control Excited‐State Prototropism of Photoacids via the Acidity of Ionic Liquids

Excited-state proton transfer reactions I. Fundamentals and intermolecular reactions

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