Modulating the Inclusive and Coordinating Ability of Thiacalix[4]arene and Its Antenna Effect on Yb(3+)-Luminescence via Upper-Rim Substitution

The present work introduces the series of thiacalix[4]arenes (H(4)L) bearing different upper-rim substituents (R = H, Br, NO(2)) for rational design of ligands providing an antenna-effect on the NIR Yb(3+)-centered luminescence of their Yb(3+) complexes. The unusual inclusive self-assembly of H(3)L(−) (Br) through Br…π interactions is revealed through single-crystal XRD analysis. Thermodynamically favorable formation of dimeric complexes [2Yb(3+):2HL(3−)] leads to efficient sensitizing of the Yb(3+) luminescence for H(4)L (Br, NO(2)), while poor sensitizing is observed for ligand H(4)L (H). X-ray analysis of the single crystal separated from the basified DMF solutions of YbCl(3) and H(4)L(NO(2)) has revealed the transformation of the dimeric complexes into [4Yb(3+):2L(4−)] ones with a cubane-like cluster structure. The luminescence characteristics of the complexes in the solutions reveal the peculiar antenna effect of H(4)L(R = NO(2)), where the triplet level at 567 nm (17,637 cm(−1)) arisen from ILCT provides efficient sensitizing of the Yb(3+) luminescence.