Ir(III) Complexes with AIE Characteristics for Biological Applications

Abstract

Both biological process detection and disease diagnosis on the basis of luminescence technology can provide comprehensive insights into the mechanisms of life and disease pathogenesis and also accurately guide therapeutics. As a family of prominent luminescent materials, Ir(III) complexes with aggregation-induced emission (AIE) tendency have been recently explored at a tremendous pace for biological applications, by virtue of their various distinct advantages, such as great stability in biological media, excellent fluorescence properties and distinctive photosensitizing features. Significant breakthroughs of AIE-active Ir(III) complexes have been achieved in the past few years and great progress has been witnessed in the construction of novel AIE-active Ir(III) complexes and their applications in organelle-specific targeting imaging, multiphoton imaging, biomarker-responsive bioimaging, as well as theranostics. This review systematically summarizes the basic concepts, seminal studies, recent trends and perspectives in this area.

Exploring Structure–Activity Relationships in Photodynamic Therapy Anticancer Agents Based on Ir(III)-COUPY Conjugates

“…Transition metal complexes have emerged as promising therapeutic tools in photopharmacology due to several unique properties, including a wide range of coordination numbers, oxidation states, and geometries. , Among transition metals, Pt­(IV), Ru­(II), Rh­(III), Ir­(III), and Os­(II) are very attractive candidates for PDT applications since they tend to absorb in the visible region of the electromagnetic spectrum and exhibit relatively high photostability and long luminescence lifetimes (>100 ns), being an interesting alternative to PSs based on organic fluorophores on clinical use such as porphyrins or chlorins. − In this context, cyclometalated iridium­(III) complexes show excellent anticancer activities and a great potential to overcome some of the main drawbacks of conventional platinum-based chemotherapy (i.e., resistance and toxic side effects). , Such metal complexes are likely good candidates for PDT applications as they combine appealing photophysical and photochemical properties within a single compound, including large Stokes’ shifts, high luminescent quantum yield, and high efficient singlet oxygen production upon light irradiation. Photosensitizers based on cyclometalated Ir­(III) complexes have been used also as photocatalysts in systems for photocatalytic hydrogen evolution reactions. , However, most reported cyclometalated iridium­(III) complexes are quite cytotoxic in the dark and only activatable with short wavelengths of light, which compromises further development of efficient PDT agents.…”

AIE-active cyclometalated iridium(iii) complexes for the detection of lipopolysaccharides and wash-free imaging of bacteria

“…LPS or LTA) and the selective discrimination, imaging, and elimination of Gram-negative and Gram-positive pathogenic bacteria due to their various advantages such as kinetic inertness, positive charge, tunable photophysical and photochemical properties, generation of high levels of reactive oxygen species, the ease of synthesis, etc . 39–43…”

“…which make them excellent candidates for applications in organic light-emitting diodes, biosensing, bioimaging and therapy. 2,[33][34][35][36][37][38][39][40][41][42][43][44][45][46][47][48] These AIEgen metal complexes can interact with bacteria or their pathogenic components through various noncovalent modes such as electrostatic interactions, hydrogen bonds, van der Waals forces and hydrophobic interactions. 2 For example, Ding and Yu's groups have developed an AIE-active cationic Pt(II) complex [Pt(N^N^N)Cl] + , where N^N^N is 2,6-bis(benzimidazol-2′-yl)pyridine with hexaethylene glycol methyl ether groups, which demonstrated sensing of LPS and rapid wash-free discrimination of Gram-negative and Gram-positive bacteria.…”

“…LPS or LTA) and the selective discrimination, imaging, and elimination of Gram-negative and Gram-positive pathogenic bacteria due to their various advantages such as kinetic inertness, positive charge, tunable photophysical and photochemical properties, gene-ration of high levels of reactive oxygen species, the ease of synthesis, etc. [39][40][41][42][43] In this work, we have made an effort to develop three cationic AIE-active cyclometalated iridium(III) complexes for rapid detection of bacterial endotoxin (or LPS) in aqueous medium and the wash-free imaging of bacteria (Scheme 1). The complexes can detect endotoxin at a nanomolar concentration within 5 min.…”

Aggregation-Induced Near-Infrared Emission and Electrochemiluminescence of an Iridium(III) Complex for Ampicillin Sodium Sensing

“…Due to the high emission quantum efficiency, colorful emission properties, high stability and low cytotoxicity, iridium­(III) complexes are widely used in electroluminescence, sensing, AIE and dye-sensitized solar cells. − A series of metal iridium­(III) complexes with AIE activity were synthesized by using ĈN-type bidentate ligands as cyclometaled ligands and triazole pyridine derivatives as auxiliary ligands by Su’s group, and it showed that AIE activity mainly came from the charge transfer intraligand ( 3 ILCT) excited state . A kind of binuclear iridium­(III) Shiff base complexes were developed by Bryce’s group, and it was found that there were some interactions between benzene rings, which made the geometric structure more planar, and activated AIE phenomenon .…”