Exceptionally Long‐Lived Luminescence Emitted from TbIII Ion Caged in an AgI–TbIII–Thiacalix[4]arene Supramolecular Complex in Water

Abstract The compositions and photophysical properties of luminescent ternary complexes of thiacalix[4]arene‐ p ‐sulfonate (TCAS), Tb III , and Ag I ions were determined. At pH 6, Ag I 2 ⋅Tb III 2 ⋅TCAS 2 formed. Moreover, at pH 10, in the presence of a 20‐fold excess of Ag I and a 50‐fold excess of TCAS with respect to Tb III , Ag I 2 ⋅Tb III ⋅TCAS 2 formed as the main luminescent species. The structure of these complexes was proposed: two TCAS ligands are linked by two S–Ag I –S linkages to adopt a double‐cone supramolecular structure. Furthermore, each Tb III 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 Ag I 2 ⋅Tb III 2 ⋅TCAS 2 (0.16) was almost equal to that of Tb III ⋅TCAS, but the luminescence lifetime τ of the former (=1.09 ms) was larger than that of the latter. For Ag I 2 ⋅Tb III ⋅TCAS 2 , 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 Tb III (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 Tb III ion is shielded by a supramolecular cage that expels coordinated water molecules responsible for luminescence quenching.