TY - JOUR
T1 - Exceptionally long-lived luminescence emitted from TbIII ion caged in an AgI-TbIII-thiacalix[4]arene supramolecular complex in water
AU - Iki, Nobuhiko
AU - Ohta, Munehiro
AU - Horiuchi, Takayuki
AU - Hoshino, Hitoshi
PY - 2008/5/5
Y1 - 2008/5/5
N2 - 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.
AB - 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.
KW - Calixarenes
KW - Energy transfer
KW - Luminescence
KW - Silver
KW - Terbium
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U2 - 10.1002/asia.200700298
DO - 10.1002/asia.200700298
M3 - Article
C2 - 18386266
AN - SCOPUS:44449155763
VL - 3
SP - 849
EP - 853
JO - Chemistry - An Asian Journal
JF - Chemistry - An Asian Journal
SN - 1861-4728
IS - 5
ER -