Energy transfer luminescence of Tb3+ ion complexed with calix[4]arenetetrasulfonate and the thia and sulfonyl analogue. The effect of bridging groupsElectronic supplementary information (ESI) available: emission spectra of Sm3+ and Dy3+ ions complexed with 2; emission spectra of Sm3+, Eu3+ and Dy3+ complexed with 3; continuous variation curves for the Tb3+ complexes with 2 and 3. See http://www.rsc.org/suppdata/p2/b0/b009151k/

New analogues of calix[4]arenetetrasulfonate (1) were prepared, in which the methylene bridges are replaced by S (2) and SO2 (3). The complexation ability of these calixarene ligands 1–3 toward Tb3+ ion and luminescence properties of the resulting complexes were examined. All the ligands formed complexes with lanthanide ions (Pr3+, Sm3+, Eu3+, Tb3+ and Dy3+), among which the Tb3+ complex exhibited strong energy transfer luminescence. The pH dependence of the luminescence intensity suggested that the analogues 2 and 3 possess higher complexation ability towards Tb3+ than the parent 1, which should be ascribed to the higher acidity of the phenolic OH groups as well as the coordinating ability of the bridging groups S and SO2. The composition of the complexes of 2 and 3 was determined to be Tb3+·2 and Tb3+·3 by a molar ratio method. The photophysical properties such as emission lifetimes (τ) and quantum yields (Φ) of the complexes were estimated. Both Tb3+·2 and Tb3+·3 gave comparable τ values (0.7 ms), which are larger than that of Tb3+·(1)2 (0.6 ms). Comparison of their lifetimes in D2O solution suggested that Tb3+·2 and Tb3+·3 have four to five coordinated water molecules responsible for quenching. On the other hand, complex Tb3+·2 gave the largest Φ value (0.15), whereas Tb3+·(1)2 and Tb3+·3 gave very close Φ values (0.12 and 0.13, respectively). The results of this study showed that thiacalix[4]arenetetrasulfonate 2 and the sulfonyl analogue 3 are promising candidates for the scaffold to construct luminescence devices from the viewpoint of the higher complexation ability and luminescent performance.