Lanthanide-containing functional complexes have found a variety of applications in materials science and biomedicine because of their unique electroptical and magnetic properties. However, the poor stability and solubility in water of multi-component lanthanide organic assemblies significantly limit their practical applications. We report here a series of water-stable anionic Ln2nL3n-type (n = 2, 3, 4, and 5) lanthanide organic polyhedra (LOPs) constructed by deprotonation self-assembly of three fully-conjugated ligands (H4L1 and H4L2a/b) featuring a 2,6-pyridine bitetrazolate chelating moiety. The outcomes of the LOPs were found to be very sensitive toward the reaction conditions including base, metal source, solvents and concentrations as characterized by a combination of NMR, high-resolution ESI-MS and X-ray crystallography. Ligands H4L2a/b manifested an excellent sensitization toward lanthanide ions (Ln = EuIII and TbIII), with high luminescent quantum yields for Tb8L2a12 (Φ = 11.17% in water) and Eu8L2b12 (Φ = 76.75% in DMSO) measured in polar solvents. Furthermore, due to the giant molecular weight and rigidity of the polyhedral skeleton, Gd8L2b12 showed a very high longitudinal relaxivity (r1) of 400.53 mM-1S-1. The performance of Gd8L2b12 as potential magnetic resonance imaging contrast agents (CAs) in vivo was evaluated with much longer retention time in the tumor sites compared with the commercial GdIII-based CAs. Dual-modal imaging potential has also been demonstrated with the mixed Eu/Gd LOPs. Our results not only provide a new design route toward water-stable multi-nuclear lanthanide organic assemblies but also offer potential candidates of supramolecular-edifices for bioimaging and drug delivery.

中文翻译：

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用于发光标记和磁共振成像的配位组装水溶性阴离子镧系元素有机多面体

含镧系元素的功能配合物由于其独特的电学和磁学性质，在材料科学和生物医学中得到了广泛的应用。然而，多组分镧系元素有机组装体在水中的稳定性和溶解性较差，极大地限制了它们的实际应用。我们在此报告了一系列由三个全共轭配体（H4L1 和 H4L2a/b）的去质子化自组装构建的水稳定阴离子 Ln2nL3n 型（n = 2、3、4 和 5）镧系元素有机多面体（LOP）具有 2,6-吡啶联四唑盐螯合部分。发现 LOP 的结果对反应条件非常敏感，包括碱、金属源、溶剂和浓度，其特征在于 NMR、高分辨率 ESI-MS 和 X 射线晶体学的组合。配体 H4L2a/b 对镧系元素离子（Ln = EuIII 和 TbIII）表现出极好的敏感性，在 Tb8L2a12（水中 Φ = 11.17%）和 Eu8L2b12（极性 DMSO 中 Φ = 76.75%）的发光量子产率很高。此外，由于多面体骨架的巨大分子量和刚性，Gd8L2b12 显示出非常高的纵向弛豫率 (r1)，为 400.53 mM-1S-1。与基于 GdIII 的商业 CA 相比，Gd8L2b12 作为体内潜在磁共振成像造影剂 (CA) 的性能被评估为在肿瘤部位具有更长的保留时间。混合 Eu/Gd LOP 也证明了双模态成像潜力。