Fine-Tuned Visible and Near-Infrared Luminescence on Self-Assembled Lanthanide-Organic Tetrahedral Cages with Triazole-Based Chelates.

Abstract

The construction of well-defined lanthanide complexes emitting in both the visible and near-infrared regions is of great importance due to their widespread applications in phosphors, light-emitting diodes, biosensors/probes, optical communications, etc. In comparison to the well-known mononuclear and dinuclear lanthanide complexes, multinuclear lanthanide supramolecular edifices with bright luminescence are still scarce. Herein, we report the coordination self-assembly of strongly luminescent lanthanide-organic tetrahedral Ln4L4 cages with a series of tris(tridentate) ligands based on the triazole chelates. Among them, the new ligand L3 with triazole-pyridine-triazole (TPT) chelates manifests an excellent sensitization toward all of the lanthanide ions (Ln = Pr, Nd, Sm, Eu, Tb, Dy, Ho, Er, Tm, Yb) that emit in both the visible and near-infrared regions, with a record luminescent quantum yield for Tb4(L3)4 (Φ = 82%) being obtained. In contrast, ligands with amido-pyridine-triazole (APT) or TPA chelates show much weaker sensitization ability. Energy levels for all ligands were measured, and TD-DFT calculations were employed to shed light on the sensitization mechanism. Finally, white-light emission systems formed by combining the desired luminescent compounds have been demonstrated. Our strongly luminescent LOPs provide new candidates for photochemical supramolecular devices.