Unraveling the mechanism of the photodeprotection reaction of 8-bromo- and 8-chloro-7-hydroxyquinoline caged acetates

Jiani Ma, Adam C. Rea, Huiying An, Chensheng Ma, Xiangguo Guan, Ming De Li, Tao Su, Chi Shun Yeung, Kyle T. Harris, Yue Zhu, Jameil L. Nganga, Olesya D. Fedoryak, Timothy Dore, David Lee Phillips

    Research output: Contribution to journalArticle

    Abstract

    Photoremovable protecting groups (PPGs) when conjugated to biological effectors forming "caged compounds" are a powerful means to regulate the action of physiologically active messengers in vivo through 1-photon excitation (1PE) and 2-photon excitation (2PE). Understanding the photodeprotection mechanism is important for their physiological use. We compared the quantum efficiencies and product outcomes in different solvent and pH conditions for the photolysis reactions of (8-chloro-7-hydroxyquinolin-2-yl) methyl acetate (CHQ-OAc) and (8-bromo-7-hydroxyquinolin-2-yl)methyl acetate (BHQ-OAc), representatives of the quinoline class of phototriggers for biological use, and conducted nanosecond time-resolved spectroscopic studies using transient emission (ns-EM), transient absorption (ns-TA), transient resonance Raman (ns-TR 2), and time-resolved resonance Raman (ns-TR 3) spectroscopies. The results indicate differences in the photochemical mechanisms and product outcomes, and reveal that the triplet excited state is most likely on the pathway to the product and that dehalogenation competes with release of acetate from BHQ-OAc, but not CHQ-OAc. A high fluorescence quantum yield and a more efficient excited-state proton transfer (ESPT) in CHQ-OAc compared to BHQ-OAc explain the lower quantum efficiency of CHQ-OAc relative to BHQ-OAc.

    Original languageEnglish (US)
    Pages (from-to)6854-6865
    Number of pages12
    JournalChemistry - A European Journal
    Volume18
    Issue number22
    DOIs
    StatePublished - May 29 2012

    Fingerprint

    Acetates
    Quantum efficiency
    Excited states
    Photons
    Dehalogenation
    Proton transfer
    Photolysis
    Quantum yield
    Fluorescence
    Spectroscopy
    8-chloro-7-hydroxyquinoline
    methyl acetate
    quinoline
    8-bromo-7-hydroxyquinoline
    TR-2 mycotoxin

    Keywords

    • cage compounds
    • photodeprotection
    • proton transfer
    • quinoline
    • time-resolved spectroscopy

    ASJC Scopus subject areas

    • Chemistry(all)

    Cite this

    Unraveling the mechanism of the photodeprotection reaction of 8-bromo- and 8-chloro-7-hydroxyquinoline caged acetates. / Ma, Jiani; Rea, Adam C.; An, Huiying; Ma, Chensheng; Guan, Xiangguo; Li, Ming De; Su, Tao; Yeung, Chi Shun; Harris, Kyle T.; Zhu, Yue; Nganga, Jameil L.; Fedoryak, Olesya D.; Dore, Timothy; Phillips, David Lee.

    In: Chemistry - A European Journal, Vol. 18, No. 22, 29.05.2012, p. 6854-6865.

    Research output: Contribution to journalArticle

    Ma, J, Rea, AC, An, H, Ma, C, Guan, X, Li, MD, Su, T, Yeung, CS, Harris, KT, Zhu, Y, Nganga, JL, Fedoryak, OD, Dore, T & Phillips, DL 2012, 'Unraveling the mechanism of the photodeprotection reaction of 8-bromo- and 8-chloro-7-hydroxyquinoline caged acetates', Chemistry - A European Journal, vol. 18, no. 22, pp. 6854-6865. https://doi.org/10.1002/chem.201200366
    Ma, Jiani ; Rea, Adam C. ; An, Huiying ; Ma, Chensheng ; Guan, Xiangguo ; Li, Ming De ; Su, Tao ; Yeung, Chi Shun ; Harris, Kyle T. ; Zhu, Yue ; Nganga, Jameil L. ; Fedoryak, Olesya D. ; Dore, Timothy ; Phillips, David Lee. / Unraveling the mechanism of the photodeprotection reaction of 8-bromo- and 8-chloro-7-hydroxyquinoline caged acetates. In: Chemistry - A European Journal. 2012 ; Vol. 18, No. 22. pp. 6854-6865.
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    abstract = "Photoremovable protecting groups (PPGs) when conjugated to biological effectors forming {"}caged compounds{"} are a powerful means to regulate the action of physiologically active messengers in vivo through 1-photon excitation (1PE) and 2-photon excitation (2PE). Understanding the photodeprotection mechanism is important for their physiological use. We compared the quantum efficiencies and product outcomes in different solvent and pH conditions for the photolysis reactions of (8-chloro-7-hydroxyquinolin-2-yl) methyl acetate (CHQ-OAc) and (8-bromo-7-hydroxyquinolin-2-yl)methyl acetate (BHQ-OAc), representatives of the quinoline class of phototriggers for biological use, and conducted nanosecond time-resolved spectroscopic studies using transient emission (ns-EM), transient absorption (ns-TA), transient resonance Raman (ns-TR 2), and time-resolved resonance Raman (ns-TR 3) spectroscopies. The results indicate differences in the photochemical mechanisms and product outcomes, and reveal that the triplet excited state is most likely on the pathway to the product and that dehalogenation competes with release of acetate from BHQ-OAc, but not CHQ-OAc. A high fluorescence quantum yield and a more efficient excited-state proton transfer (ESPT) in CHQ-OAc compared to BHQ-OAc explain the lower quantum efficiency of CHQ-OAc relative to BHQ-OAc.",
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    AU - Ma, Jiani

    AU - Rea, Adam C.

    AU - An, Huiying

    AU - Ma, Chensheng

    AU - Guan, Xiangguo

    AU - Li, Ming De

    AU - Su, Tao

    AU - Yeung, Chi Shun

    AU - Harris, Kyle T.

    AU - Zhu, Yue

    AU - Nganga, Jameil L.

    AU - Fedoryak, Olesya D.

    AU - Dore, Timothy

    AU - Phillips, David Lee

    PY - 2012/5/29

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    N2 - Photoremovable protecting groups (PPGs) when conjugated to biological effectors forming "caged compounds" are a powerful means to regulate the action of physiologically active messengers in vivo through 1-photon excitation (1PE) and 2-photon excitation (2PE). Understanding the photodeprotection mechanism is important for their physiological use. We compared the quantum efficiencies and product outcomes in different solvent and pH conditions for the photolysis reactions of (8-chloro-7-hydroxyquinolin-2-yl) methyl acetate (CHQ-OAc) and (8-bromo-7-hydroxyquinolin-2-yl)methyl acetate (BHQ-OAc), representatives of the quinoline class of phototriggers for biological use, and conducted nanosecond time-resolved spectroscopic studies using transient emission (ns-EM), transient absorption (ns-TA), transient resonance Raman (ns-TR 2), and time-resolved resonance Raman (ns-TR 3) spectroscopies. The results indicate differences in the photochemical mechanisms and product outcomes, and reveal that the triplet excited state is most likely on the pathway to the product and that dehalogenation competes with release of acetate from BHQ-OAc, but not CHQ-OAc. A high fluorescence quantum yield and a more efficient excited-state proton transfer (ESPT) in CHQ-OAc compared to BHQ-OAc explain the lower quantum efficiency of CHQ-OAc relative to BHQ-OAc.

    AB - Photoremovable protecting groups (PPGs) when conjugated to biological effectors forming "caged compounds" are a powerful means to regulate the action of physiologically active messengers in vivo through 1-photon excitation (1PE) and 2-photon excitation (2PE). Understanding the photodeprotection mechanism is important for their physiological use. We compared the quantum efficiencies and product outcomes in different solvent and pH conditions for the photolysis reactions of (8-chloro-7-hydroxyquinolin-2-yl) methyl acetate (CHQ-OAc) and (8-bromo-7-hydroxyquinolin-2-yl)methyl acetate (BHQ-OAc), representatives of the quinoline class of phototriggers for biological use, and conducted nanosecond time-resolved spectroscopic studies using transient emission (ns-EM), transient absorption (ns-TA), transient resonance Raman (ns-TR 2), and time-resolved resonance Raman (ns-TR 3) spectroscopies. The results indicate differences in the photochemical mechanisms and product outcomes, and reveal that the triplet excited state is most likely on the pathway to the product and that dehalogenation competes with release of acetate from BHQ-OAc, but not CHQ-OAc. A high fluorescence quantum yield and a more efficient excited-state proton transfer (ESPT) in CHQ-OAc compared to BHQ-OAc explain the lower quantum efficiency of CHQ-OAc relative to BHQ-OAc.

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    KW - time-resolved spectroscopy

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