Supramolecular assembly confined purely organic room temperature phosphorescence and its biological imaging

Abstract

Purely organic room temperature phosphorescence, especially in aqueous solution, is attracting increasing attention owing to its large Stokes shift, long lifetime, low preparation cost, low toxicity, good processing performance advantages, and broad application value. This review mainly focuses on macrocyclic (cyclodextrin and cucurbituril) hosts, nanoassembly, and macromolecule (polyether) confinement-driven RTP. As an optical probe, the assembly and the two-stage assembly strategy can realize the confined purely organic RTP and achieve energy transfer and light-harvesting from fluorescence to delayed fluorescence or phosphorescence. This supramolecular assembly is widely applied for luminescent materials, cell imaging, and other fields because it effectively avoids oxygen quenching. In addition, the near-infrared excitation, near-infrared emission, and in situ imaging of purely organic room temperature phosphorescence in assembled confinement materials are also prospected.

Scheme 1. Schematic illustration of the Jablonski diagram of the emissive processes of phosphorescence (Φ_phos: the quantum yield of phosphorescence; Φ_isc: the quantum yield of intersystem crossing; τ_phos: the lifetime of phosphorescence; k^fluo_r: the fluorescence decay rate constant; k^fluo_nr: the fluorescence nonradiative rate constant; k_isc: the intersystem crossing rate constant from S1 to T1; k^phos_r: the phosphorescence decay rate constant; k^phos_nr: the phosphorescence nonradiative rate constant).

Fig. 1. Schematic illustration of photo-controlled reversible RTP pseudorotaxane in aqueous solutions.

Fig. 2. Schematic illustration of photo-controlled reversible RTP supramolecular assembly based on azo-β-CD and α-BrNp in aqueous solutions.

Fig. 3. Schematic illustration of construction of the compound structure of the photoresponsive supramolecular RTP gel based on β-CD and bromonaphthalene.

Fig. 4. Schematic illustration of construction of photocontrolled RTP supramolecular assembly in aqueous solution through the poly-BrNpA/γ-CD/poly-azo system.

Fig. 5. Schematic illustration of the construction of a pH-controlled molecular shuttle in aqueous solution based on CB[7] and the 6-bromoisoquinoline derivative.

Fig. 6. Schematic illustration of the construction of supramolecular aqueous RTP assembly based on CB[7] and ANBrNpA.

Fig. 7. Schematic illustration of construction of photoresponsive RTP supramolecular assembly by CB[7] and amphiphilic 6-bromoisoquinoline.

Fig. 8. Schematic illustration of construction of the TBP-CB[8] 2 : 2 quaternary RTP supramolecular assembly via CB[8] and TBP.

Fig. 9. Schematic illustration of the self-assembly of the ultralong water-soluble purely organic RTP supramolecular polymer by supramolecular and macromolecular effects.

Fig. 10. Schematic illustration of the construction of “two-end blocked” pseudorotaxane based on CB[8] and DA-PY.

Fig. 11. Schematic illustration of construction of supramolecular phosphorescent pins via the assembly of CB[8] and alkyl-bridged phenylpyridinium salts.

Fig. 12. Schematic illustration of the construction of photoresponsive linear supramolecular aggregates based on CB[8] and anthracene-modified bromophenylpyridinium salt.

Fig. 13. Schematic illustration of the construction of photocontrolled supramolecular phosphorescence energy transfer based on the diarylethene-modified bromophenylpyridinium salt.

Fig. 14. Schematic illustration of the construction of light-harvesting phosphorescence energy transfer supramolecular assembly via CD-PY, CB[8], RhB, and HA-ADA.

Fig. 15. Schematic illustration of the construction of light-harvesting phosphorescence energy transfer supramolecular assembly via SC4AH, CB[8], and bromonaphthalene-modified methoxypyridine.

Fig. 16. Schematic illustration of construction of a two-stage light-harvesting phosphorescence energy transfer supramolecular assembly via SC4AH, CB[8], and di-bromophthalimide derivative.

Fig. 17. Schematic illustration of the structures of phosphorescent compounds C–Br and C–C4–Br.

Fig. 18. Schematic illustration of the structures of the different substituents (H-NpCzBF₂, Br-NpCzBF₂, and I-NpCzBF₂) based on difluoroboron β-diketonate (BF2bdk) and carbazole.

Fig. 19. Schematic illustration of the phosphorescence self-assembly of UPy-functionalized BrNpA-UPy.

Fig. 20. Schematic illustration of the proposed LAPONITE® ionic hybrid self-assembly.

Fig. 21. Schematic illustration of the LP-based phosphorescence harvesting assembly.

Fig. 22. Schematic illustration of the phosphorescent molecular structure.

Fig. 23. Schematic illustration of the structure of pegylated BNPs based on BF2dbm(I)PLLA (4) and mPEG-b-PDLA (5).

Fig. 24. Schematic illustration of the phosphorescent molecular structure and cell imaging.

Fig. 25. Schematic illustration of the cell permeabilization mechanism and AIE molecular structure.

Fig. 26. Schematic illustration of 10-phenyl-10H-phenothiazine-5,5-dioxide-based derivative structures, and the photograph of the corresponding molecular crystalline phosphorescence.

Fig. 27. Schematic illustration of the molecular design strategy, and the preparation method of phosphorescent systems.

Fig. 28. Schematic illustration of PRET for in vivo imaging.