Optical and electron paramagnetic resonance studies of the excited triplet states of UV-B absorbers: 2-ethylhexyl salicylate and homomenthyl salicylate

Kazuto Sugiyama, Takumi Tsuchiya, Azusa Kikuchi, Mikio Yagi

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    Abstract

    1) states of UV-B absorbers, 2-ethylhexyl salicylate (EHS) and homomenthyl salicylate (HMS), and their deprotonated anions (EHS- and HMS-) were determined through measurements of phosphorescence and electron paramagnetic resonance (EPR) spectra in rigid solutions at 77 K. The observed T1 energies of EHS and HMS are higher than those of butylmethoxydibenzoylmethane, the most widely used UV-A absorber, and octyl methoxycinnamate, the most widely used UV-B absorber. The T1 states of EHS, HMS, EHS- and HMS- were assigned to almost pure 3ππ∗ state from the observed T1 lifetimes and zero-field splitting parameters. EHS and HMS with an intramolecular hydrogen bond show a photoinduced phosphorescence enhancement in ethanol at 77 K. The EPR signals of the T1 states of EHS and HMS also increase in intensity with UV-irradiation time (photoinduced EPR enhancement). The T1 lifetimes of EHS and HMS at room temperature were determined through triplet-triplet absorption measurements in ethanol. The quantum yields of singlet oxygen production by EHS and HMS were determined by using time-resolved near-IR phosphorescence.]]>

    Original languageEnglish
    Pages (from-to)1651-1659
    Number of pages9
    JournalPhotochemical and Photobiological Sciences
    Volume14
    Issue number9
    DOIs
    StatePublished - 2015 Jun 16

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    salicylate
    electron spin resonance
    ethanol
    energy
    anion
    irradiation
    hydrogen
    oxygen
    temperature

    ASJC Scopus subject areas

    • Physical and Theoretical Chemistry

    Cite this

    Optical and electron paramagnetic resonance studies of the excited triplet states of UV-B absorbers : 2-ethylhexyl salicylate and homomenthyl salicylate. / Sugiyama, Kazuto; Tsuchiya, Takumi; Kikuchi, Azusa; Yagi, Mikio.

    In: Photochemical and Photobiological Sciences, Vol. 14, No. 9, 16.06.2015, p. 1651-1659.

    Research output: Contribution to journalArticle

    Sugiyama, Kazuto; Tsuchiya, Takumi; Kikuchi, Azusa; Yagi, Mikio / Optical and electron paramagnetic resonance studies of the excited triplet states of UV-B absorbers : 2-ethylhexyl salicylate and homomenthyl salicylate.

    In: Photochemical and Photobiological Sciences, Vol. 14, No. 9, 16.06.2015, p. 1651-1659.

    Research output: Contribution to journalArticle

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    title = "Optical and electron paramagnetic resonance studies of the excited triplet states of UV-B absorbers: 2-ethylhexyl salicylate and homomenthyl salicylate",
    author = "Kazuto Sugiyama and Takumi Tsuchiya and Azusa Kikuchi and Mikio Yagi",
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    AU - Yagi,Mikio

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    AB - The energy levels and lifetimes of the lowest excited triplet (T1) states of UV-B absorbers, 2-ethylhexyl salicylate (EHS) and homomenthyl salicylate (HMS), and their deprotonated anions (EHS- and HMS-) were determined through measurements of phosphorescence and electron paramagnetic resonance (EPR) spectra in rigid solutions at 77 K. The observed T1 energies of EHS and HMS are higher than those of butylmethoxydibenzoylmethane, the most widely used UV-A absorber, and octyl methoxycinnamate, the most widely used UV-B absorber. The T1 states of EHS, HMS, EHS- and HMS- were assigned to almost pure 3ππ∗ state from the observed T1 lifetimes and zero-field splitting parameters. EHS and HMS with an intramolecular hydrogen bond show a photoinduced phosphorescence enhancement in ethanol at 77 K. The EPR signals of the T1 states of EHS and HMS also increase in intensity with UV-irradiation time (photoinduced EPR enhancement). The T1 lifetimes of EHS and HMS at room temperature were determined through triplet-triplet absorption measurements in ethanol. The quantum yields of singlet oxygen production by EHS and HMS were determined by using time-resolved near-IR phosphorescence.

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