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 Brπ 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.