Coordination-Assembled Water-Soluble Anionic Lanthanide Organic Polyhedra for Luminescent Labeling and Magnetic Resonance Imaging

Abstract

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 multicomponent lanthanide organic assemblies significantly limit their practical applications. We report here a series of water-stable anionic Ln2n L3n -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 formation reactions 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 Tb8L2a 12 (Φ = 11.2% in water) and Eu8L2b 12 (Φ = 76.8% in DMSO) measured in polar solvents. Furthermore, due to the giant molecular weight and rigidity of the polyhedral skeleton, Gd8L2b 12 showed a very high longitudinal relaxivity (r 1) of 400.53 mM–1S–1. The performance of Gd8L2b 12 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 multinuclear lanthanide organic assemblies but also offer potential candidates of supramolecular-edifices for bioimaging and drug delivery.

Perylene Diimide-Based Multicomponent Metallacages as Photosensitizers for Visible Light-Driven Photocatalytic Oxidation Reaction

“…[12][13][14][15][16][17][18][19] This strategy takes the highly directional metal-coordination bonds to prepare SCCs spontaneously and endows the SCCs with high structural and functional diversity. [20][21][22][23][24][25][26][27][28] Especially, the preparation of photosensitizers using this method not only avoids their self-aggregation through the formation of geometric structures, but also facilitates the intersystem crossing owing to the introduction of heavy metal atoms, giving high 1 O 2 generation ability and photostability. [29][30][31][32][33][34] Moreover, different buliding blocks capable of generating 1 O 2 can be integrated into a single metallacage.…”

Metal‐Organic Cages with Missing Linker Defects

“…The formation of cages 1 – 3 were also suggested by 1 H NMR spectra, which display more complicated signals than the ligands (Figure S4). By dissolving the crystalline samples, clearly distinct 1 H NMR patterns were observed, but they were too complex to be assigned clearly due to substantial line‐broadening and overlapping of the signals [10c, 15] . Nevertheless, the diffusion‐ordered 1 H NMR spectra (DOSY) indicated the formation of a single assembly with a single vertical trace with the diffusion coefficient D =3.24×10 −10 m 2 s −1 (hydrodynamic radius is about 19.6 Å), D =4.32×10 −10 m 2 s −1 (hydrodynamic radius is about 14.7 Å) and D =3.45×10 −10 m 2 s −1 (hydrodynamic radius is about 18.4 Å) for cages 1 , 2 and 3 , respectively (Figure S5).…”

Functional Material Systems Based on Soft Cages

“…Cages built using luminescent lanthanide ions as nodes can be directly used in biomedical imaging without encapsulating other luminescent guests. Wang et al reported a series of water‐soluble anionic Ln 2n L 3n ‐type (n=2, 3, 4 and 5) polyhedral complexes, among which Eu III , Tb III and Gd III in Ln 8 L 2b 12 cubes in aqueous media showed bright luminescence [36] . As shown in Figure 6c, these cages alone, without encapsulating guests, holds promising application as luminescent and MRI agents.…”