Photochemistry of nonconjugated diketones: internal self-quenching and energy transfer

Wagner, Peter J.; Frerking, Harlan W.

doi:10.1139/v95-253

Cited by 14 publications

(11 citation statements)

References 32 publications

(45 reference statements)

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“…Potential interactions between the excited diketo form and the ground state enol form was investigated by studying the quenching of 3 BM‐DBM‐Me* by BM‐DBM. An efficient rate constant of 6.5 × 10 9 m −1 × s −1 was obtained; hence, triplet–triplet energy transfer can be proposed, which would be in agreement with the triplet energies described in the literature for the related diketo and the enol forms of dibenzoyl methane derivatives at 72 kcal mol −1 × s −1 and 59 kcal × mol −1 , respectively (4,17).…”

Section: Resultssupporting

confidence: 83%

A Blocked Diketo Form of Avobenzone: Photostability, Photosensitizing Properties and Triplet Quenching by a Triazine‐derived UVB‐filter

Paris

Lhiaubet‐Vallet

Jiménez

et al. 2009

Photochem & Photobiology

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Novel sunscreens are required providing active protection in the UVA and UVB regions. On the other hand, there is an increasing concern about the photosafety of UV filters, as some of them are not sufficiently photostable. Avobenzone is one of the most frequently employed sunscreen ingredients, but it has been reported to partially decompose after irradiation. In the present work, photophysical and photochemical studies on a methylated avobenzone-derivative have shown that the diketo form is responsible for photodegradation. A transient absorption was observed at 380 nm after laser flash photolysis excitation at 308 nm. It was assigned to the triplet excited state of the diketo form, as inferred from quenching by oxygen and b-carotene. This transient also interacted with key building blocks of biomolecules by triplet-triplet energy transfer (in the case of thymidine) or electron transfer processes (for 2¢-deoxyguanosine, tryptophan and tyrosine). Irradiation of the avobenzone derivative in the presence of a triazine UV-B filter (E-35852) diminished the undesirable effects of the compound by an efficient quenching of the triplet excited state. Thus, sunscreen formulations including triplet quenchers could provide effective protection from the potential phototoxic and photoallergic effects derived from poor photostability of avobenzone.

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Section: Resultssupporting

confidence: 83%

A Blocked Diketo Form of Avobenzone: Photostability, Photosensitizing Properties and Triplet Quenching by a Triazine‐derived UVB‐filter

Paris

Lhiaubet‐Vallet

Jiménez

et al. 2009

Photochem & Photobiology

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“…To reconcile the different lifetimes for the racemic and meso diastereomers, the effect of intramolecular self-quenching and intramolecular triplet energy transfer on the lifetimes for the two diastereomers should be considered. The importance of these two factors has been examined in detail by Wagner and co-workers in analogous diketones …”

Section: Discussionmentioning

confidence: 99%

Modulation of Lifetimes and Diastereomeric Discrimination in Triplet-Excited Substituted Butane-1,4-diones through Intramolecular Charge-Transfer Quenching

et al. 1999

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Triplet lifetimes have been determined for the diastereomers of a broad set of butane-1,4-dione derivatives (1 − 3). A remarkable dependence of lifetimes on conformational preferences is revealed in that the lifetimes are shorter for the meso diastereomers of 1 − 3 than those for the racemic ones. The intramolecular β-phenyl quenching is promoted in the case of meso diastereomers by virtue of the gauche relationship between the excited carbonyl group and the β-aryl ring, while a distal arrangement in the lowest energy conformation (H -anti) in racemic diastereomers prevents such a deactivation. The involvement of charge transfer in the intramolecular β-phenyl quenching is suggested by the correlation of the triplet lifetimes of the meso diastereomers of compounds 2 with the nature of the substituent on the β-phenyl rings. In the case of racemic diastereomers, p-methoxy substitution on the β-phenyl ring (2-OCH 3 , 3-OCH 3 ) also led to a decrease of the triplet lifetimes when compared to those of the nonsubstituted compounds (2-H, 3-H). This shortening is accounted for by the deactivation of a small proportion of the excited molecules through β-phenyl quenching. In addition to the above factors, the lifetimes in the case of meso diastereomers can further be controlled by increasing the energy spacing between the T1 and T2 states, since β-phenyl quenching occurs from the latter for compounds 2 and 3. Through a rational conformational control, a surprisingly long triplet lifetime (300 ns) has been measured for the first time for a purely n,π* triplet-excited β-phenylpropiophenone dimer (1 -rac).

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“…Rapid intramolecular energy transfer and self-quenching have been reported for analogous diketones . For 1 , the energy transfer operates in both diastereomers such that each carbonyl group is excited for half of the time until deactivation occurs and, hence, cannot be responsible for the observed differences.…”

mentioning

confidence: 99%

Remarkable Discrimination in the Triplet Lifetimes of the Diastereomers of 1,4-Bis(p-methoxyphenyl)- 2,3-diphenylbutan-1,4-dione

1997

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Photochemistry of nonconjugated diketones: internal self-quenching and energy transfer

Cited by 14 publications

References 32 publications

A Blocked Diketo Form of Avobenzone: Photostability, Photosensitizing Properties and Triplet Quenching by a Triazine‐derived UVB‐filter

A Blocked Diketo Form of Avobenzone: Photostability, Photosensitizing Properties and Triplet Quenching by a Triazine‐derived UVB‐filter

Modulation of Lifetimes and Diastereomeric Discrimination in Triplet-Excited Substituted Butane-1,4-diones through Intramolecular Charge-Transfer Quenching

Remarkable Discrimination in the Triplet Lifetimes of the Diastereomers of 1,4-Bis(p-methoxyphenyl)- 2,3-diphenylbutan-1,4-dione

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