Exceptionally long-lived luminescence emitted from TbIII ion caged in an AgI-TbIII-thiacalix[4]arene supramolecular complex in water

Nobuhiko Iki, Munehiro Ohta, Takayuki Horiuchi, Hitoshi Hoshino

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18 Citations (Scopus)

Abstract

The compositions and photophysical properties of luminescent ternary complexes of thiacalix[4]arene-p-sulfonate (TCAS), TbIII, and Ag I ions were determined. At pH 6, AgI2· TbIII2·TCAS2 formed. Moreover, at pH 10, in the presence of a 20-fold excess of AgI and a 50-fold excess of TCAS with respect to TbIII, AgI2·Tb III·TCAS2 formed as the main luminescent species. The structure of these complexes was proposed: two TCAS ligands are linked by two S-AgI-S linkages to adopt a double-cone supramolecular structure. Furthermore, each TbIII ion in the former complex accepts O -, S, O- donation, whereas in the latter, the Tb III center accepts eightfold O- donation. The luminescence quantum yield (Φ) of AgI2·Tb III2·TCAS2 (0.16) was almost equal to that of TbIII·TCAS, but the luminescence lifetime τ of the former (= 1.09 ms) was larger than that of the latter. For AgI 2·TbIII·TCAS2, the yield Φ (= 0.11) was small, which is attributed to the low efficiency of photosensitization (η = 0.11). However, the τ value (4.61 ms) was exceptionally large and almost equal to the natural luminescence lifetime of TbIII (4.7 ms), which is due to the absence of coordinating water molecules (q = 0.1). This is compatible with the proposed structure in which the TbIII ion is shielded by a supramolecular cage that expels coordinated water molecules responsible for luminescence quenching.

Original languageEnglish
Pages (from-to)849-853
Number of pages5
JournalChemistry - An Asian Journal
Volume3
Issue number5
DOIs
Publication statusPublished - 2008 May 5

Keywords

  • Calixarenes
  • Energy transfer
  • Luminescence
  • Silver
  • Terbium

ASJC Scopus subject areas

  • Biochemistry
  • Organic Chemistry

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