Recent Advances in Organometallic NIR Iridium(III) Complexes for Detection and Therapy

Abstract

Iridium(III) complexes are emerging as a promising tool in the area of detection and therapy due to their prominent photophysical properties, including higher photostability, tunable phosphorescence emission, long-lasting phosphorescence, and high quantum yields. In recent years, much effort has been devoted to develop novel near-infrared (NIR) iridium(III) complexes to improve signal-to-noise ratio and enhance tissue penetration. In this review, we summarize different classes of organometallic NIR iridium(III) complexes for detection and therapy, including cyclometalated ligand-enabled NIR iridium(III) complexes and NIR-dye-conjugated iridium(III) complexes. Moreover, the prospects and challenges for organometallic NIR iridium(III) complexes for targeted detection and therapy are discussed.

Keywords: NIR; detection; iridium(III) complexes; therapy.

Figure 1

Schematic diagram of application of organometallic NIR iridium(III) complexes.

Figure 2

Two main strategies of designing NIR iridium(III) complexes. (1) Cyclometalated ligand-enabled NIR iridium(III) complexes. (2) NIR dye conjugation-enabled NIR iridium(III) complexes.

Figure 3

Chemical structures of 1–3.

Figure 4

Construction of the multimodal HClO imaging probe. Reproduced with permission from Ref. [66] Copyright 2023 American Chemical Society.

Figure 5

Chemical structures of 4b–5b.

Figure 6

Schematic illustration of the mechanism of 7a response to Cys and Hcy. Red simply represents enhanced luminescence of the complex. Reproduced with permission from Ref. [68]. Copyright 2017 Royal Society of Chemistry.

Figure 7

Chemical structures of 8a–8c.

Figure 8

Chemical structures of 9–12.

Figure 9

Chemical structures of 13–16b.

Figure 10

Chemical structures of 17–19.

Figure 11

Chemical structures of complexes 20a and 20b, and the illustration of cell death pathways induced by 20b. Reproduced with permission from Ref. [84]. Copyright 2021 John Wiley and Sons (Hoboken, NJ, USA).

Figure 12

Chemical structure of 21.

Figure 13

Chemical structures of 22a–23.

Figure 14

Chemical structures of 24a–25b.

Figure 15

Chemical structures of 26a–27a.

Figure 16

Schematic representation of the iridium(III)-coumarin conjugate 27b. Reproduced with permission from Ref. [89]. Copyright 2019 John Wiley and Sons.

Figure 17

Schematic illustration of the working mechanism of iridium(III) complex-derived polymeric micelles for combined PDT and PTT. Reproduced with permission from Ref. [32]. Copyright 2021 John Wiley and Sons.

Figure 18

The structure and anticancer mechanism of 29 for NIR I-type PDT and PTT are depicted schematically. Reproduced with permission from Ref. [108]. Copyright 2020 John Wiley and Sons.