Exceptionally long-lived luminescence emitted Ag-I-Tb-III-Thiacalix[4]arene supramolecular from Tb-III ion caged in an complex in water

The compositions and photo-physical properties of luminescent ternary complexes of thiacalix[4]-arene-p-sulfonate (TCAS), Tb-III, and Ag-I ions were determined. At pH 6, Ag-2(I)center dot Tb-2(III)center dot TCAS(2) formed. Moreover, at pH 10, in the presence of a 20-fold excess of Ag-I and a 50-fold excess of WAS with respect to Tb-III, Ag-2(I)center dot Tb-III center dot TCAS(2) formed as the main luminescent species. The structure of these complexes was proposed: two WAS 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 (phi) of Ag-2(I)center dot Tb-2(III)center dot TCAS(2) (0.16) was almost equal to that of Tb-III.TCAS, but the luminescence lifetime tau of the former (= 1.09 ms) was larger than that of the latter. For Ag-2(I)center dot Tb(III center dot)TCAS(2), the yield phi (=0.11.) was small, which is attributed to the low efficiency of photosensitization (eta=0.11). However, the T 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.