Luminescence and Electron Paramagnetic Resonance Studies of the Excited States of a UV Absorber, 2-Methylphenyl 2-Naphthoate

Kikuchi, Azusa; Yagi, Mikio

doi:10.1246/cl.2009.770

Cited by 5 publications

(2 citation statements)

References 11 publications

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“…It is especially important to determine the energy level of the lowest excited triplet (T 1 ) state of individual UV absorber because triplet−triplet energy transfer from a donor to an acceptor will occur between the UV absorbers. We have determined the energy levels of the T 1 states of UV absorbers by measuring the phosphorescence spectra in rigid solutions at 77 K and elucidated the nature of the T 1 states of the UV absorbers. − …”

Section: Introductionmentioning

confidence: 99%

Optical and Electron Paramagnetic Resonance Studies of the Excited States of 4-tert-Butyl-4′-Methoxydibenzoylmethane and 4-tert-Butyl-4′-Methoxydibenzoylpropane

2009

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The excited states of 4-tert-butyl-4'-methoxydibenzoylmethane (BM-DBM) and 4-tert-butyl-4'-methoxydibenzoylpropane (BM-DBP), the model of the keto form of BM-DBM, have been studied through measurements of UV absorption, fluorescence, phosphorescence, and electron paramagnetic resonance spectra in ethanol at 77 K. The energy levels and lifetimes of the lowest excited triplet (T(1)) states of BM-DBP, dibenzoylpropane (DBP), the model of the keto form of dibenzoylmethane (DBM), and the keto and enol forms of BM-DBM and DBM were determined. The energy level of the T(1) state of the keto form is much higher than that of the enol form in BM-DBM. The effect of tautomerization on the T(1) lifetime is small in DBM but large in BM-DBM. The methoxy and tert-butyl groups play an important role in lengthening the T(1) lifetimes of BM-DBP and the keto form of BM-DBM. The nature of the T(1) states of the keto and enol forms of BM-DBM can be explained in terms of the mixing of the (3)npi* and (3)pipi* states. The observed energy levels and the lifetimes of the T(1) states of the UV absorbers provide a useful suggestion for designing more photostable UV absorbers.

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Section: Introductionmentioning

confidence: 99%

Optical and Electron Paramagnetic Resonance Studies of the Excited States of 4-tert-Butyl-4′-Methoxydibenzoylmethane and 4-tert-Butyl-4′-Methoxydibenzoylpropane

2009

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“…[2][3][4][5][6][7][8][9][10][11] It is important to determine the energy levels of the excited states of individual UV absorber because the energy transfer is one of the most important interactions between the UV absorbers. [12][13][14][15] Recently, it has been shown that the excited triplet state of the keto form is responsible for photodegradation of BM-DBM. 6 It is especially important to determine the energy levels of the lowest excited triplet (T 1 ) states of individual UV absorbers because, in general, triplet energy transfer will occur when the T 1 energy of the acceptor is equal to or lower than that of the donor.…”

Section: Introductionmentioning

confidence: 99%

Photoexcited triplet states of new UV absorbers, cinnamic acid 2-methylphenyl esters

Kikuchi

Saito

Mori

et al. 2011

Photochem Photobiol Sci

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Phosphorescence spectra of nonphosphorescent or very weakly phosphorescent new UV absorbers, 2-methylphenyl cinnamate (MePC), 2-methylphenyl 4-methoxycinnamate (MePMC) and 2-methylphenyl 4-ethoxycinnamate (MePEC) have been observed by using external heavy atom effects of ethyl iodide in ethanol at 77 K. The lowest excited triplet (T(1)) energies of these new UV absorbers are lower than those of a widely used UV-A absorber, 4-tert-butyl-4'-methoxydibenzoylmethane (BM-DBM), in both keto and enol forms. The intermolecular triplet-triplet energy transfer from photolabile BM-DBM to MePMC was observed by measuring the time-resolved phosphorescence spectra. Electron paramagnetic resonance spectra have been observed for the T(1) states of these new UV absorbers in ethanol at 77 K by using benzophenone as a triplet sensitizer. The observed T(1) lifetimes, zero-field splitting (ZFS) parameters and molecular orbital calculations of the ZFS parameters suggest that T(1) states of these new UV absorbers posses mainly (3)ππ* character. The deactivation processes of the lowest excited singlet (S(1)) states are predominantly fluorescence and internal conversion to the ground (G) states in MePMC and MePEC, while the main deactivation process of the S(1) state of MePC is internal conversion to the G state. The molar absorption coefficients of MePMC and MePEC in the UV-A and UV-B regions are larger than that of most widely used UV-B absorber, octyl methoxycinnamate.

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Direct observation of the intermolecular triplet–triplet energy transfer from UV-A absorber 4-tert-butyl-4′-methoxydibenzoylmethane to UV-B absorber octyl methoxycinnamate

Kikuchi

Yagi

2011

Chemical Physics Letters

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Luminescence and Electron Paramagnetic Resonance Studies of the Excited States of a UV Absorber, 2-Methylphenyl 2-Naphthoate

Cited by 5 publications

References 11 publications

Optical and Electron Paramagnetic Resonance Studies of the Excited States of 4-tert-Butyl-4′-Methoxydibenzoylmethane and 4-tert-Butyl-4′-Methoxydibenzoylpropane

Optical and Electron Paramagnetic Resonance Studies of the Excited States of 4-tert-Butyl-4′-Methoxydibenzoylmethane and 4-tert-Butyl-4′-Methoxydibenzoylpropane

Photoexcited triplet states of new UV absorbers, cinnamic acid 2-methylphenyl esters

Direct observation of the intermolecular triplet–triplet energy transfer from UV-A absorber 4-tert-butyl-4′-methoxydibenzoylmethane to UV-B absorber octyl methoxycinnamate

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