Kinetics of photoinduced electron transfer reactions of ruthenium(II) complexes and phenols, tyrosine, N-acetyl-tyrosine and tryptophan in aqueous solutions measured with modulated fluorescence spectroscopy

Truong Nguyen Xuan, Stephan Landgraf, Günter Grampp

Research output: Contribution to journalArticleResearchpeer-review

Abstract

Photooxidation kinetics of phenol, 1-naphthol, 2-naphthol, tyrosine (TyrOH) and N-acetyl-tyrosine (AcTyrOH), tryptophan (TrpH) by ruthenium(II) polypyridyl complexes: [Ru(bpy)3]Cl2 (1), [Ru(phen)3]Cl2 (2), [Ru(bpy)(phen)(bpg)]Cl2 (3), and [Ru(dpq)2(bxbg)]Cl2 (4) where bpy is 2,2′-bipyridine, phen – 1,10-phenanthroline, bpg – bipyridine-glycoluril, dpq – dipyrido[3,2-d:2′,3′-f]quinoxaline, and bxbg – bis(o-xylene)bipyridine-glycoluril are investigated. Rate constants have been measured by steady-state luminescence and phase-modulation fluorometry in aqueous solutions at different pH's. The rates for the oxidation of the phenols and phenolic aromatic amino acids spreads over a wide range from 4.2 × 10^6 to 6.8 × 10^9 M^-1 s^−1, depending on pH and the nature of solutes. At pH > pKa of the quenchers, the presence of reactive species (PhO−) in the alkaline solutions is accounted for the rapid ET rates. In the pH range between 4 and 10 (pH < pKa), the ETPT mechanism becomes dominate and the rate constants are relatively low. It reveals that the important parameters that influence the quenching reaction rates, others than the driving forces ∆ G0 are the steric and hydrophobic interactions arising from the structure of the compounds. This is clearly seen in the case of photoreaction between the Ru(phen)3 2+ complex and AcTyrOH. Phen ligands and acetyl group cause a steric effect, but strengthen the hydrophobic interactions and thus promote the quenching process. The pH-dependent equation of the observed rate constant for PhOH/AcTyrOH oxidation is expressed as a sum of rates for its protonated, neutral and deprotonated forms.
Original languageEnglish
Pages (from-to)28-34
JournalJournal of photochemistry and photobiology / B
Volume166
DOIs
Publication statusPublished - 2017

Keywords

    Cite this

    @article{c0bd371cf2444a51b81fdbb54615319b,
    title = "Kinetics of photoinduced electron transfer reactions of ruthenium(II) complexes and phenols, tyrosine, N-acetyl-tyrosine and tryptophan in aqueous solutions measured with modulated fluorescence spectroscopy",
    abstract = "Photooxidation kinetics of phenol, 1-naphthol, 2-naphthol, tyrosine (TyrOH) and N-acetyl-tyrosine (AcTyrOH), tryptophan (TrpH) by ruthenium(II) polypyridyl complexes: [Ru(bpy)3]Cl2 (1), [Ru(phen)3]Cl2 (2), [Ru(bpy)(phen)(bpg)]Cl2 (3), and [Ru(dpq)2(bxbg)]Cl2 (4) where bpy is 2,2′-bipyridine, phen – 1,10-phenanthroline, bpg – bipyridine-glycoluril, dpq – dipyrido[3,2-d:2′,3′-f]quinoxaline, and bxbg – bis(o-xylene)bipyridine-glycoluril are investigated. Rate constants have been measured by steady-state luminescence and phase-modulation fluorometry in aqueous solutions at different pH's. The rates for the oxidation of the phenols and phenolic aromatic amino acids spreads over a wide range from 4.2 × 10^6 to 6.8 × 10^9 M^-1 s^−1, depending on pH and the nature of solutes. At pH > pKa of the quenchers, the presence of reactive species (PhO−) in the alkaline solutions is accounted for the rapid ET rates. In the pH range between 4 and 10 (pH < pKa), the ETPT mechanism becomes dominate and the rate constants are relatively low. It reveals that the important parameters that influence the quenching reaction rates, others than the driving forces ∆ G0 are the steric and hydrophobic interactions arising from the structure of the compounds. This is clearly seen in the case of photoreaction between the Ru(phen)3 2+ complex and AcTyrOH. Phen ligands and acetyl group cause a steric effect, but strengthen the hydrophobic interactions and thus promote the quenching process. The pH-dependent equation of the observed rate constant for PhOH/AcTyrOH oxidation is expressed as a sum of rates for its protonated, neutral and deprotonated forms.",
    keywords = "Photoinduced electron transfer, Ruthenium(II) polypyridine complexes, Phenols, Tyrosine, N-acetyl-tyrosine, Tryptophan, Steric, Hydrophobic interaction, Phase-modulated fluorescence",
    author = "{Nguyen Xuan}, Truong and Stephan Landgraf and G{\"u}nter Grampp",
    year = "2017",
    doi = "10.1016/j.jphotobiol.2016.11.007",
    language = "English",
    volume = "166",
    pages = "28--34",
    journal = "Journal of photochemistry and photobiology / B",
    issn = "1011-1344",
    publisher = "Elsevier B.V.",

    }

    TY - JOUR

    T1 - Kinetics of photoinduced electron transfer reactions of ruthenium(II) complexes and phenols, tyrosine, N-acetyl-tyrosine and tryptophan in aqueous solutions measured with modulated fluorescence spectroscopy

    AU - Nguyen Xuan, Truong

    AU - Landgraf, Stephan

    AU - Grampp, Günter

    PY - 2017

    Y1 - 2017

    N2 - Photooxidation kinetics of phenol, 1-naphthol, 2-naphthol, tyrosine (TyrOH) and N-acetyl-tyrosine (AcTyrOH), tryptophan (TrpH) by ruthenium(II) polypyridyl complexes: [Ru(bpy)3]Cl2 (1), [Ru(phen)3]Cl2 (2), [Ru(bpy)(phen)(bpg)]Cl2 (3), and [Ru(dpq)2(bxbg)]Cl2 (4) where bpy is 2,2′-bipyridine, phen – 1,10-phenanthroline, bpg – bipyridine-glycoluril, dpq – dipyrido[3,2-d:2′,3′-f]quinoxaline, and bxbg – bis(o-xylene)bipyridine-glycoluril are investigated. Rate constants have been measured by steady-state luminescence and phase-modulation fluorometry in aqueous solutions at different pH's. The rates for the oxidation of the phenols and phenolic aromatic amino acids spreads over a wide range from 4.2 × 10^6 to 6.8 × 10^9 M^-1 s^−1, depending on pH and the nature of solutes. At pH > pKa of the quenchers, the presence of reactive species (PhO−) in the alkaline solutions is accounted for the rapid ET rates. In the pH range between 4 and 10 (pH < pKa), the ETPT mechanism becomes dominate and the rate constants are relatively low. It reveals that the important parameters that influence the quenching reaction rates, others than the driving forces ∆ G0 are the steric and hydrophobic interactions arising from the structure of the compounds. This is clearly seen in the case of photoreaction between the Ru(phen)3 2+ complex and AcTyrOH. Phen ligands and acetyl group cause a steric effect, but strengthen the hydrophobic interactions and thus promote the quenching process. The pH-dependent equation of the observed rate constant for PhOH/AcTyrOH oxidation is expressed as a sum of rates for its protonated, neutral and deprotonated forms.

    AB - Photooxidation kinetics of phenol, 1-naphthol, 2-naphthol, tyrosine (TyrOH) and N-acetyl-tyrosine (AcTyrOH), tryptophan (TrpH) by ruthenium(II) polypyridyl complexes: [Ru(bpy)3]Cl2 (1), [Ru(phen)3]Cl2 (2), [Ru(bpy)(phen)(bpg)]Cl2 (3), and [Ru(dpq)2(bxbg)]Cl2 (4) where bpy is 2,2′-bipyridine, phen – 1,10-phenanthroline, bpg – bipyridine-glycoluril, dpq – dipyrido[3,2-d:2′,3′-f]quinoxaline, and bxbg – bis(o-xylene)bipyridine-glycoluril are investigated. Rate constants have been measured by steady-state luminescence and phase-modulation fluorometry in aqueous solutions at different pH's. The rates for the oxidation of the phenols and phenolic aromatic amino acids spreads over a wide range from 4.2 × 10^6 to 6.8 × 10^9 M^-1 s^−1, depending on pH and the nature of solutes. At pH > pKa of the quenchers, the presence of reactive species (PhO−) in the alkaline solutions is accounted for the rapid ET rates. In the pH range between 4 and 10 (pH < pKa), the ETPT mechanism becomes dominate and the rate constants are relatively low. It reveals that the important parameters that influence the quenching reaction rates, others than the driving forces ∆ G0 are the steric and hydrophobic interactions arising from the structure of the compounds. This is clearly seen in the case of photoreaction between the Ru(phen)3 2+ complex and AcTyrOH. Phen ligands and acetyl group cause a steric effect, but strengthen the hydrophobic interactions and thus promote the quenching process. The pH-dependent equation of the observed rate constant for PhOH/AcTyrOH oxidation is expressed as a sum of rates for its protonated, neutral and deprotonated forms.

    KW - Photoinduced electron transfer

    KW - Ruthenium(II) polypyridine complexes

    KW - Phenols

    KW - Tyrosine

    KW - N-acetyl-tyrosine

    KW - Tryptophan

    KW - Steric

    KW - Hydrophobic interaction

    KW - Phase-modulated fluorescence

    U2 - 10.1016/j.jphotobiol.2016.11.007

    DO - 10.1016/j.jphotobiol.2016.11.007

    M3 - Article

    VL - 166

    SP - 28

    EP - 34

    JO - Journal of photochemistry and photobiology / B

    JF - Journal of photochemistry and photobiology / B

    SN - 1011-1344

    ER -