Effects of hydrogen-bonding interaction and polarity on emission spectrum of naphthalene-triethylamine in mixed solvent

Guo Bin Xie, Yoshimi Sueishi, Shunzo Yamamoto

Research output: Contribution to journalArticle

1 Citation (Scopus)

Abstract

The effects of the protic and aprotic polar solvents on the emission spectrum of the naphthalene-triethylamine system in THF were studied under conditions of steady-state illumination. The fluorescence spectrum of the naphthalene-triethylamine system consists of two emission bands, the fluorescence band of naphthalene (band A, 329 nm) and the emission band of the exciplex (band B, 468 nm). The intensities of both the emission bands decrease with increasing the solvent polarity. The intensity of band B also decreases due to the hydrogen-bonding interaction between triethylamine and protic solvent, while that of band A increases. It is thus suggested that the quenching of naphthalene fluorescence by triethylamine in THF occurs through the charge transfer and electron transfer reactions. The spectral changes upon the increase of solvent polarity can be explained by the dependences of the equilibrium constant between exciplex and ion-pair and the rate constant for the electron transfer reaction from triethylamine to the excited naphthalene on the relative permittivity of solvent. It is shown that the formation of intermolecular hydrogen-bonding between triethylamine and protic solvent suppresses the quenching reaction by the decrease in free amine. Acetonitrile has only a polar effect and trichloroacetic acid only a hydrogen-bonding (or protonation) effect, while alcohols have both the effects. The effects of alcohols could be separated into the effects of solvent polarity and intermolecular hydrogen-bonding interaction quantitatively.

Original languageEnglish
Pages (from-to)606-611
Number of pages6
JournalChemical Research in Chinese Universities
Volume20
Issue number5
Publication statusPublished - Sep 2004

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Hydrogen bonds
Fluorescence
Quenching
Alcohols
Trichloroacetic Acid
Electrons
Protonation
Equilibrium constants
naphthalene
triethylamine
Amines
Charge transfer
Rate constants
Permittivity
Lighting
Ions

Keywords

  • Fluorescence spectrum
  • Hydrogenbonding interaction
  • Naphthalene-triethylamine
  • Solvent effect
  • Solvent polarity

ASJC Scopus subject areas

  • Chemistry(all)

Cite this

Effects of hydrogen-bonding interaction and polarity on emission spectrum of naphthalene-triethylamine in mixed solvent. / Xie, Guo Bin; Sueishi, Yoshimi; Yamamoto, Shunzo.

In: Chemical Research in Chinese Universities, Vol. 20, No. 5, 09.2004, p. 606-611.

Research output: Contribution to journalArticle

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N2 - The effects of the protic and aprotic polar solvents on the emission spectrum of the naphthalene-triethylamine system in THF were studied under conditions of steady-state illumination. The fluorescence spectrum of the naphthalene-triethylamine system consists of two emission bands, the fluorescence band of naphthalene (band A, 329 nm) and the emission band of the exciplex (band B, 468 nm). The intensities of both the emission bands decrease with increasing the solvent polarity. The intensity of band B also decreases due to the hydrogen-bonding interaction between triethylamine and protic solvent, while that of band A increases. It is thus suggested that the quenching of naphthalene fluorescence by triethylamine in THF occurs through the charge transfer and electron transfer reactions. The spectral changes upon the increase of solvent polarity can be explained by the dependences of the equilibrium constant between exciplex and ion-pair and the rate constant for the electron transfer reaction from triethylamine to the excited naphthalene on the relative permittivity of solvent. It is shown that the formation of intermolecular hydrogen-bonding between triethylamine and protic solvent suppresses the quenching reaction by the decrease in free amine. Acetonitrile has only a polar effect and trichloroacetic acid only a hydrogen-bonding (or protonation) effect, while alcohols have both the effects. The effects of alcohols could be separated into the effects of solvent polarity and intermolecular hydrogen-bonding interaction quantitatively.

AB - The effects of the protic and aprotic polar solvents on the emission spectrum of the naphthalene-triethylamine system in THF were studied under conditions of steady-state illumination. The fluorescence spectrum of the naphthalene-triethylamine system consists of two emission bands, the fluorescence band of naphthalene (band A, 329 nm) and the emission band of the exciplex (band B, 468 nm). The intensities of both the emission bands decrease with increasing the solvent polarity. The intensity of band B also decreases due to the hydrogen-bonding interaction between triethylamine and protic solvent, while that of band A increases. It is thus suggested that the quenching of naphthalene fluorescence by triethylamine in THF occurs through the charge transfer and electron transfer reactions. The spectral changes upon the increase of solvent polarity can be explained by the dependences of the equilibrium constant between exciplex and ion-pair and the rate constant for the electron transfer reaction from triethylamine to the excited naphthalene on the relative permittivity of solvent. It is shown that the formation of intermolecular hydrogen-bonding between triethylamine and protic solvent suppresses the quenching reaction by the decrease in free amine. Acetonitrile has only a polar effect and trichloroacetic acid only a hydrogen-bonding (or protonation) effect, while alcohols have both the effects. The effects of alcohols could be separated into the effects of solvent polarity and intermolecular hydrogen-bonding interaction quantitatively.

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