.Highly Efficient Near-Infrared-Emitting Lanthanide(Iii) Complexes Formed By Heterogeneous Self-Assembly Of Ag-I, Ln(Iii), And Thiacalix[4]Arene-P-Tetrasulfonate In Aqueous Solution (Ln(Iii) = Nd-Iii, Yb-Iii)

Heterogeneous self-assembly of thiacalix[4]arene-p-tetrasulfonate (TCAS), Ag-I, and Ln(III) (= Nd-III, Yb-III) in aqueous solutions conveniently afforded ternary complexes emitting Ln(III)-centered luminescence in the near-infrared (NIR) region. A solution-state study revealed that the Ag-I-Nd-III-TCAS system gave a complex Ag-4(I)center dot Nd-III center dot TCAS(2) in a wide pH range of 6-12. In contrast, the Ag-I-Yb-III-TCAS system gave Ag-2(I)center dot Yb-2(III)center dot TCAS(2) at a pH of around 6 and Ag-2(I)center dot Yb-III center dot TCAS(2) at a pH of approximately 9.5. The structures of the Yb-III complexes were proposed based on comparison with known Ag-I-Tb-III-TCAS complexes that show the same self-assembly behavior. In Ag-2(I)center dot Yb-2(III)center dot TCAS(2), two TCAS ligands sandwiched a cyclic array of a Ag-I-Ag-I-Yb-III-Yb-III core. In Ag-2(I)center dot Yb-III center dot TCAS(2), Yb-III was accommodated in an O-8 cube consisting of eight phenolate O- groups from two TCAS ligands linked by two S-Ag-S linkages. Crystallographic analysis of Ag-4(I)center dot Nd-III center dot TCAS(2) revealed that the structure was similar to Ag-2(I)center dot Yb-III center dot TCAS(2) but that it had four instead of two S-Ag-S linkages. The number of water molecules coordinating to Ln(III) (q) estimated on the basis of the luminescent lifetimes was as follows: Ag-4(I)center dot Nd-III center dot TCAS(2), 0; Ag-2(I)center dot Yb-2(III)center dot TCAS(2), 2.4; and Ag-2(I)center dot Yb-III center dot TCAS(2), 0. These findings were compatible with the solution-state structures. The luminescent quantum yield (Phi) for Ag-4(I)center dot Nd-III center dot TCAS(2) was 4.9 X 10(-4), which is the second largest value ever reported in H2O. These findings suggest that the O-8 cube is an ideal environment to circumvent deactivation via O-H oscillation of coordinating water. The Phi values for Ag-2(I)center dot Yb-2(III)center dot TCAS(2) and Ag-2(I)center dot Yb-III center dot TCAS(2) were found to be 3.8 X 10(-4) and 3.3 X 10(-3), respectively, reflecting the q value. Overall, these results indicate that the ternary systems have the potential for a noncovalent strategy via self-assembly of the multidentate ligand, Ln(III), and an auxiliary metal ion to obtain a highly efficient NIR-emissive Ln(III) complex that usually relies on elaborate covalent linkage of a chromophore and multidentate ligands to expel coordinating water.