Determination of the fluorescence quantum yields of some 2-substituted benzothiazoles

Kirkbright, G. F.; Spillane, Dominic E. M.; ANTHONY, K.; Brown, Robert G.; Hepworth, John D.; Hodgson, Kevin; West, Michael

doi:10.1021/ac00273a024

Cited by 17 publications

(6 citation statements)

References 20 publications

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“…In this paper, we have investigated the fluorescence emission properties of HBT-R nanoparticles, and have compared them with some solid HBT-Rs reported by M. A. West et al 32 and Scheme 1 Schematic representation of the ESIPT process of HBT-R derivatives.…”

Section: Introductionmentioning

confidence: 99%

Excited-state intramolecular proton transfer on 2-(2′-hydroxy-4′-R-phenyl)benzothiazole nanoparticles and fluorescence wavelength depending on substituent and temperature

Kim

Roh²,

Jung

et al. 2010

Photochem Photobiol Sci

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The fluorescence emission properties of 2-(2'-hydroxy-4'-R-phenyl)benzothiazole (HBT-R) nanoparticles with different substituents (R = -COOH, -H, -CH(3), -OH, and -OCH(3)) were investigated using spectroscopic and theoretical methods. HBT-Rs displayed dual enol and keto (excited-state intramolecular proton transfer (ESIPT)) emissions in nonpolar solvents. The spectral change of their ESIPT emissions was affected differently by the electron donating (or withdrawing) power of the substituents; a bathochromic shift for the electron donating group and a hypsochromic shift in electron withdrawing group. In addition, the changes in energy levels calculated by the ab initio method were consistent with the spectral shifts of HBT-R in solution. We prepared aggregated HBT-R nanoparticles using a simple reprecipitation process in tetrahydrofuran-water solvents. The ESIPT emission of aggregated HBT-R nanoparticles was strongly enhanced (over 45 times) compared to those of monomer HBT-Rs in toluene, as markedly shifted ESIPT emissions are observed at longer wavelength without any quenching by self-absorption. Aggregated HBT-R nanoparticles showed longer lifetimes than those of monomer molecules. The temperature effect on the aqueous dispersion of the aggregated HBT-R nanoparticles was also explored. It shows a fluorescent ratiometric change in a range of temperature from 7 to 65 degrees C. A mechanism of a temperature-dependent equilibrium between the nanoparticles and the solvated enols is proposed for the emission color change.

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Section: Introductionmentioning

confidence: 99%

Excited-state intramolecular proton transfer on 2-(2′-hydroxy-4′-R-phenyl)benzothiazole nanoparticles and fluorescence wavelength depending on substituent and temperature

Kim

Roh²,

Jung

et al. 2010

Photochem Photobiol Sci

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“…Similar studies carried out on other molecules have clearly established that the energy barrier for excited state proton transfer is nearly equal to 120cm -1. These results have been further substantiated by the lack of temperature dependence for this kind of proton transfer in the temperature range of 298-77 K and ESIPT is even observed in the solid state (Kirkbright et al 1984). Similarly one can also expect an energy barrier for the reverse proton transfer from the tautomer to the normal molecule in the ground state.…”

Section: Fluorescence Spectramentioning

confidence: 76%

Intra- and intermolecular proton transfer reactions in 2-phenyl substituted benzazoles

Dogra

1992

Proc. Indian Acad. Sci. (Chem. Sci.)

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The present review describes the salient features of inter-and intramolecular proton transfer reactions of 2-(2'-aminophenyl)-', 2-(3'-aminophenyl)-, 2-(4'-aminophenyl)-, 2-(2'-hydroxyphenyl)-, 2-(3'-hydroxyphenyl)-and 2-(4'-hydroxyphenyl)-benzimidazoles, benzoxazoles and benzothiazoles. Fluorescence quantum yield of the phototautomer produced by the intramolecular hydrogen bonding decreases on going from benzimidazole to benzoxazole to benzothiazole. This indicates that the rate of internal conversion increases in the order of compounds as mentioned above. The biprotonic phototautomerism or the presence of intermolecular proton transfer has led to the formation of (i) nonfluorescent zwitterions in case of hydroxyphenyl derivatives and the ground state precursor of this species in neutral molecules, (ii) nonfluorescent monoanions from fluorescent monoanions and (iii) nonfluorescent monocations from monocations in case of aminophenyl derivatives. In the case of 2-(4'-aminophenyl)-substituted compounds, the first protonation has always led to the formation of two types of monocations; one by protonating the amino group and the other by protonating the tertiary nitrogen atom. The former is more stable in aqueous media and the latter in non-polar media.

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“…The first step of the synthesis involved the addition of a 2 : 1 aq H 2 O 2 /aq HCl solution to 2-aminothiophenol and o-vanilin in EtOH, which formed HMBT in good yield (68%). [22][23][24] With HMBT in hand, trifluoromethanesulfonic anhydride was then added dropwise into a solution of HMBT in DCM at À78 1C under argon, NEt 3 was subsequently added to the reaction. This reaction proceeded smoothly furnishing HMBT-LW in good yield (52%) (Scheme 2).…”

Section: Omentioning

confidence: 99%

ESIPT-based fluorescence probe for the ratiometric detection of superoxide

Liu

Han

et al. 2019

New J. Chem.

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Determination of the fluorescence quantum yields of some 2-substituted benzothiazoles

Cited by 17 publications

References 20 publications

Excited-state intramolecular proton transfer on 2-(2′-hydroxy-4′-R-phenyl)benzothiazole nanoparticles and fluorescence wavelength depending on substituent and temperature

Excited-state intramolecular proton transfer on 2-(2′-hydroxy-4′-R-phenyl)benzothiazole nanoparticles and fluorescence wavelength depending on substituent and temperature

Intra- and intermolecular proton transfer reactions in 2-phenyl substituted benzazoles

ESIPT-based fluorescence probe for the ratiometric detection of superoxide

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