Phase transition thermochromism based on C-H acidity of 4-alkylflavylium compounds in Pluronic F-127

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Abstract

In moderately acidic water/ethanol solutions, 7-(naphthalen-2-ylmethyl)-5,6-dihydrobenzo[c]xanthen12-ium perchlorate shows C-H proton acidity giving rise to an ethylenic base species, instead of the hydration products of the typical flavylium network of chemical reactions, hemiketal, cis-chalcone and trans-chalcone. The kinetics of this acid-base process is much slower, k(obs)(s(-1)) = 3.5 x 10(-3) + 0.16[H(+)], than those commonly observed for O-H deprotonation. In the presence of the triblock copolymer Pluronic F-127, the ethylenic base is dramatically stabilized shifting the pK(a) from 1.35 (in ethanol : water (1 : 1) to -0.35. Taking profit from the well-described temperature dependence of this polymer, a phase transition thermochromic system was achieved. The system was cycled between 5 and 35 degrees C with negligible changes in absorbance after 20 cycles.
Original languageUnknown
Pages (from-to)16628-16637
JournalJournal Of Materials Chemistry
Volume21
Issue number41
DOIs
Publication statusPublished - 1 Jan 2011

Keywords

    Cite this

    @article{07b61af03f6a4806808108787b68c2c6,
    title = "Phase transition thermochromism based on C-H acidity of 4-alkylflavylium compounds in Pluronic F-127",
    abstract = "In moderately acidic water/ethanol solutions, 7-(naphthalen-2-ylmethyl)-5,6-dihydrobenzo[c]xanthen12-ium perchlorate shows C-H proton acidity giving rise to an ethylenic base species, instead of the hydration products of the typical flavylium network of chemical reactions, hemiketal, cis-chalcone and trans-chalcone. The kinetics of this acid-base process is much slower, k(obs)(s(-1)) = 3.5 x 10(-3) + 0.16[H(+)], than those commonly observed for O-H deprotonation. In the presence of the triblock copolymer Pluronic F-127, the ethylenic base is dramatically stabilized shifting the pK(a) from 1.35 (in ethanol : water (1 : 1) to -0.35. Taking profit from the well-described temperature dependence of this polymer, a phase transition thermochromic system was achieved. The system was cycled between 5 and 35 degrees C with negligible changes in absorbance after 20 cycles.",
    keywords = "POLYMER HYDROGEL MATRIX, IONIC DYES, FLAVYLIUM SALTS, SUGAR-GEL, EXCITED-STATE, CTAB MICELLES, PH, AQUEOUS-SOLUTION, PHOTOCHROMISM, STATE PROTON-TRANSFER",
    author = "Parola, {Ant{\'o}nio Jorge Dias} and Lima, {Jo{\~a}o Carlos dos Santos Silva E Pereira de} and Pina, {Fernando Jorge da Silva}",
    year = "2011",
    month = "1",
    day = "1",
    doi = "10.1039/c1jm13348a",
    language = "Unknown",
    volume = "21",
    pages = "16628--16637",
    journal = "Journal Of Materials Chemistry",
    issn = "0959-9428",
    publisher = "Royal Society of Chemistry",
    number = "41",

    }

    TY - JOUR

    T1 - Phase transition thermochromism based on C-H acidity of 4-alkylflavylium compounds in Pluronic F-127

    AU - Parola, António Jorge Dias

    AU - Lima, João Carlos dos Santos Silva E Pereira de

    AU - Pina, Fernando Jorge da Silva

    PY - 2011/1/1

    Y1 - 2011/1/1

    N2 - In moderately acidic water/ethanol solutions, 7-(naphthalen-2-ylmethyl)-5,6-dihydrobenzo[c]xanthen12-ium perchlorate shows C-H proton acidity giving rise to an ethylenic base species, instead of the hydration products of the typical flavylium network of chemical reactions, hemiketal, cis-chalcone and trans-chalcone. The kinetics of this acid-base process is much slower, k(obs)(s(-1)) = 3.5 x 10(-3) + 0.16[H(+)], than those commonly observed for O-H deprotonation. In the presence of the triblock copolymer Pluronic F-127, the ethylenic base is dramatically stabilized shifting the pK(a) from 1.35 (in ethanol : water (1 : 1) to -0.35. Taking profit from the well-described temperature dependence of this polymer, a phase transition thermochromic system was achieved. The system was cycled between 5 and 35 degrees C with negligible changes in absorbance after 20 cycles.

    AB - In moderately acidic water/ethanol solutions, 7-(naphthalen-2-ylmethyl)-5,6-dihydrobenzo[c]xanthen12-ium perchlorate shows C-H proton acidity giving rise to an ethylenic base species, instead of the hydration products of the typical flavylium network of chemical reactions, hemiketal, cis-chalcone and trans-chalcone. The kinetics of this acid-base process is much slower, k(obs)(s(-1)) = 3.5 x 10(-3) + 0.16[H(+)], than those commonly observed for O-H deprotonation. In the presence of the triblock copolymer Pluronic F-127, the ethylenic base is dramatically stabilized shifting the pK(a) from 1.35 (in ethanol : water (1 : 1) to -0.35. Taking profit from the well-described temperature dependence of this polymer, a phase transition thermochromic system was achieved. The system was cycled between 5 and 35 degrees C with negligible changes in absorbance after 20 cycles.

    KW - POLYMER HYDROGEL MATRIX

    KW - IONIC DYES

    KW - FLAVYLIUM SALTS

    KW - SUGAR-GEL

    KW - EXCITED-STATE

    KW - CTAB MICELLES

    KW - PH

    KW - AQUEOUS-SOLUTION

    KW - PHOTOCHROMISM

    KW - STATE PROTON-TRANSFER

    U2 - 10.1039/c1jm13348a

    DO - 10.1039/c1jm13348a

    M3 - Article

    VL - 21

    SP - 16628

    EP - 16637

    JO - Journal Of Materials Chemistry

    JF - Journal Of Materials Chemistry

    SN - 0959-9428

    IS - 41

    ER -