Direct observation of alkali metal ion recognition processes at the heptane/water interface by second harmonic generation spectroscopy

Kimihisa Nochi, Akira Yamaguchi, Takashi Hayashita, Tatsuya Uchida, Norio Teramae

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27 Citations (Scopus)

Abstract

Alkali metal ion recognition with [2-hydroxy-5-(4-nitrophenylazo)phenyl]-methyl-15-crown-5 (azoprobe 1) at the heptane/water interface was investigated by in sim second harmonic generation (SHG) spectroscopy. Upon addition of alkali metal ions, the second harmonic (SH) intensity of azoprobe 1 at the heptane/water interface was found to increase selectively. The observed selectivity of K+ > Na+ > Li+> TMA + was essentially the same order as that of the extractability for alkali metal ions in the 1,2-dichloroethane/water extraction. Although the Li+ extractability by azoprobe 1 was very low in the 1,2-dichloroethane/water system, the observed increase of SH intensity suggested that the Li+ complex could distribute to some extent at the heptane/water interface. The red shift of the SHG spectra for azoprobe 1 revealed that the heptane/water interface had an intermediate polarity between those of the two solvents. The light polarization analysis of the SH intensity exhibited a clear orientation change of azoprobe 1 at the heptane/water interface on forming the alkali metal complexes. It was experimentally clarified that the Na+ and K+ complexes were flatter while the Li+ complex exhibited a lift-up orientation as compared with the free anionic azoprobe 1 at the heptane/ water interface.

Original languageEnglish
Pages (from-to)9906-9911
Number of pages6
JournalJournal of Physical Chemistry B
Volume106
Issue number38
DOIs
Publication statusPublished - 2002 Sep 26

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry

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