Tuning the photophysical properties of lanthanide(iii)/zinc(ii) 'encapsulated sandwich' metallacrowns emitting in the near-infrared range

Near-Infrared Ytterbium Complexes Based on Polycyclic Aromatic Dicarboxylate Ligands and the Solution-Processed NIR OLED with Irradiance up to 110,284 μW/m2

Since the O-H and N-H oscillators of solvent molecules attached to ytterbium ion (Yb3+) and C-H oscillators existing in the inner coordination sphere of Yb3+ would quench the excited energy of Yb(III), which leads to low quantum yields (QYs) of Yb(III) complexes, we aimed to design a ligand that could block solvent molecules and C-H oscillators out of the first coordination sphere of Yb3+. Herein, a series of novel polycyclic aromatic dicarboxylate ligands are designed and synthesized to effectively protect Yb3+ from solvent molecules and efficiently sensitize Yb3+ luminescence, while the cost and sophistication of the synthesis are satisfactory. Therein, [Yb(MO-DPyPDA)2](DIEA) exhibited a considerable QY of 5.20% and a long luminescent lifetime of 102 μs in CD3OD. The single-crystal structure demonstrates that there are no solvent molecules and C-H oscillators existing in the inner coordination sphere of Yb3+, which is conducive to alleviating the quenching effect. Meanwhile, we also carried out experiments to verify that it was thermodynamically feasible for ligands to sensitize the luminescence of center ion through internal redox processes. Moreover, several groups of near-infrared organic light-emitting diodes based on [Yb(DTFM-DPyPDA)2](DIEA) were fabricated based on the solution-processing method, and the highest irradiance of 110,284 μW/m2 was realized by optimizing the device structure.

A novel Ln3+/Al3+ metallacrown multifunctional material for latent fingerprint detection, luminescent thermometers and luminescent sensors

Lanthanide luminescent complexes are active and thriving in various research fields due to their unique optical properties, while optical materials across a wide spectral range and with multiple functions in one were rarely reported. In this work, a new class of Ln3+/Al3+ metallacrowns (MCs) were constructed with excellent luminescence properties in both the visible and near-infrared regions, and the elaborate luminescence modulation can be achieved by doping with different Ln3+ ions. Strikingly, the powder of LnMC was developed as a luminescent nanomaterial for the detection of latent fingerprints (LFPs), and even the third level details of fingerprints can be clearly recognized, which provides a reference for the identification of fingerprints in the field of criminal investigation. More importantly, TbMC and Tb0.1Sm0.9MC can be successfully used as luminescent thermometers with sensitivities of 2.51% °C-1 and 2.33% °C-1, respectively, higher than most reported values. Meanwhile, TbMC was developed as a luminescent probe for Fe3+ and 2,6-pyridinedicarboxylic acid (DPA) with low limits of detection (LOD) of 0.51 μM and 4.26 μM, respectively, representing the first example of MC with luminescence sensing. Also of note is that SmMC, Tb0.1Sm0.9MC and TbMC can be functionalized as luminescent inks and films due to their clear recognizable colours in the visible range, suggesting a new strategy for high-level anti-counterfeiting. In short, the LnMC luminescent material has wide application prospects in many fields, especially rare for multifunctional applications of small-molecule complexes with non-metal-organic frameworks.

Long story short: donor set symmetry in [Eu(DOTA)(H2O)]- crystals determines the electronic structure

Lanthanide complexes of 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid DOTA have been studied in great detail due to their use as MRI contrast agents. Since the first report from Desreux in 1980, the Ln[DOTA]^- complexes of gadolinium(III) in particular have been thoroughly investigated. The forms of the nine-coordinated [Ln(DOTA)(H₂O)]^- complexes are well known, and the ligand backbone has been used extensively to create functional MRI contrast agents, luminescent probes, and as a model system for studying the properties of lanthanide(III) ions. In solution, the photophysical properties have been mapped, but as the structures are not known, direct structure-property relationships have not been created. Here, the electronic properties of two Eu[DOTA] compounds (1 and 2) and a Eu[DOTA]-like compound (3) were studied using single-crystal luminescence spectroscopy. The donor set in the three compounds is identical (4N 4O 1O), and using the symmetry deviation value σ_ideal it was shown that the coordination geometry is close to identical. Nevertheless, the electronic properties evaluated using the luminescence spectrum were found to differ significantly between the three compounds. The magnitude of the crystal field splitting was found not to scale with the symmetry of the coordination geometry. It was concluded that the donor set dictates the splitting, yet the structure-property relationships governing the electronic properties of europium(III) ions still elude us.

Tapered Optical Fibers Coated with Rare-Earth Complexes for Quantum Applications

Crystals and fibers doped with rare-earth (RE) ions provide the basis for most of today's solid-state optical systems, from lasers and telecom devices to emerging potential quantum applications such as quantum memories and optical to microwave conversion. The two platforms, doped crystals and doped fibers, seem mutually exclusive, each having its own strengths and limitations, the former providing high homogeneity and coherence and the latter offering the advantages of robust optical waveguides. Here we present a hybrid platform that does not rely on doping but rather on coating the waveguide-a tapered silica optical fiber-with a monolayer of complexes, each containing a single RE ion. The complexes offer an identical, tailored environment to each ion, thus minimizing inhomogeneity and allowing tuning of their properties to the desired application. Specifically, we use highly luminescent Yb3+[Zn(II)MC (QXA)] complexes, which isolate the RE ion from the environment and suppress nonradiative decay channels. We demonstrate that the beneficial optical transitions of the Yb3+ are retained after deposition on the tapered fiber and observe an excited-state lifetime of over 0.9 ms, on par with state-of-the-art Yb-doped inorganic crystals.