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

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