Isomer Engineering of Lepidine-Based Iridophosphors for Far-Red Hypoxia Imaging and Photodynamic Therapy

Abstract

The development of highly efficient cyclometalated phosphorescent iridium(III) complexes is greatly promoted by their rational molecular design. Manipulating the excited states of iridophosphors could endow them with appealing photophysical properties, which play vital roles in triplet state-related photofunctional applications (e.g., electroluminescence, photodynamic therapy, etc.). In general, the most effective approach for decreasing the emission energies of iridophosphors is to extend the π-skeleton of ligands. However, the π-extension strategy often results in decreased solubility, lower synthetic yield, decreased photoluminescence quantum yield, and so forth. In this work, a simple yet efficient strategy is proposed for the effective excited-state manipulation of 2-phenyllepidine-based iridophosphors. Surprisingly, dramatic tuning of phosphorescence wavelength (∼70 nm) is achieved by simply controlling the position of a single methoxyl substituent on these iridophosphors. An oxygen-responsive iridophosphor featuring far-red emission (660 nm), long emission lifetime (1.60 μs), and high singlet oxygen quantum yield (0.73) is employed to realize accurate oxygen sensing in vitro and in vivo, and it also shows efficient photodynamic therapy in cancer cells, making it a promising candidate for the efficient image-guided photodynamic therapeutic agent. This molecular design strategy clearly demonstrates the advantages of designing novel longwavelength emissive iridophosphors without increasing the π-conjugation of the ligand.

Iridium(III)-Based Infrared Two-Photon Photosensitizers: Systematic Regulation of Their Photodynamic Therapy Efficacy

“…For YF1−4, however, most ESs with low energy level were contributed by the N ∧ N ligands, resulting in a more obvious difference in emission wavelengths from each other. 33 All Ir(III)-PSs in this study exhibited a lifetime (τ) range from 814 to 970 ns in aqueous solution (Table S7), comparable to Ir(III)-PSs recently reported by different research groups. 7,27,34−38 Such a relatively long ES lifetime can facilitate photosensitization and photoinduced electron transfer processes on light activation.…”

A narrowband red-emitting asymmetric iridium(iii) complex featuring B- and N-embedded π-conjugation units: structure, photophysics and OLED application

“…Phosphorescent metal iridium(III) complexes, as excellent room temperature phosphorescent materials, are widely used in organic light-emitting diodes (OLEDs), [1][2][3][4][5][6][7][8][9][10] chemical sensing, [11][12][13][14][15] biological imaging, [16][17][18][19][20] photocatalysts for organic reactions, [21][22][23][24] etc. Especially for phosphorescent OLEDs which can be used in flat-panel displays and lighting sources, metal iridium complexes have more advantages, including a stable octahedral coordination structure, a suitable luminescence lifetime, an adjustable luminescence color, high luminescence efficiency and exciton utilization.…”

Multicolor Emissive Phosphorescent Iridium(III) Complexes Containing L-Alanine Ligands: Photophysical and Electrochemical Properties, DFT Calculations, and Selective Recognition of Cu(II) Ions

“…Iridium complexes have gradually become the most promising phosphorescent materials due to their high PLQY (photoluminescence quantum yield) [ 9 , 10 , 11 ], easy modification of chemical structure [ 12 , 13 ], easy emission wavelength adjustment [ 14 ], and excellent chemical stability [ 15 ]. Thus, iridium complexes have been used as photosensitizers [ 16 , 17 ] and chemosensors for the detection of various analytes [ 18 , 19 ], showing excellent performance [ 20 ]. For example, Ir(III) complex ZIr2 based on di(2-picolyl)amine (DPA) as a Cu 2+ receptor was designed and synthesized, which exhibited phosphorescence quenching for addition of Cu 2+ with high selectivity and good reversibility [ 8 ].…”