The octahedron-shaped three-shell structure of the [(Ln14(H2O)W4(OH)O14)(WO4)4(GeW10O38)6]43− polyanion contains a W4 tetrahedron, a Ln14W4 tetrahedron and a Ge6W60 octahedron.
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.
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