Oral Presentation Royal Australian Chemical Institute National Congress 2026

Synthesis and Studies of Water-Soluble Luminescent Iridium(III) Complexes (136930)

Liam Barron 1 , Paul Francis 2 , Peter Barnard 1
  1. La Trobe University, Reservoir, VICTORIA, Australia
  2. Deakin University, Geelong, VICTORIA, Australia

Luminescent iridium(III) complexes have attracted significant research interest due to their favourable phosphorescence properties, and they currently have a variety of uses, including as bioimaging probes and as photo-redox catalysts.1, 2 Flagship luminescent iridium(III) complexes feature an iridium(III) metal centre decorated with aromatic ligands e.g. 2-phenylpyridine, or 2-phenylbenzothiazole and 2,2′-bipyridine. Whilst these ligands are essential for the phosphorescent properties of the iridium complexes, they also drastically impact their solubility in water and other polar solvents. Recently, the requirement for water-soluble cyclometalated iridium(III) complexes has significantly increased due to the growing demand in various fields, particularly in biological research and photo-redox catalysis where water is used as an essential and non-toxic solvent.3 Furthermore, emerging research demonstrates that water soluble iridium(III) luminophores can be useful for the control of electrochemiluminescence (ECL) reaction pathways in aqueous solutions.4

In this project, our research on the development of water-soluble iridium(III) complexes through ligand sulfonation while still retaining their favourable photophysical properties is described. Herein we present the synthesis and characterisation of a library of novel water-soluble iridium(III) complexes bearing sulfonate-modified cyclometalating ligands. A range of both homoleptic and heteroleptic iridium(III) complexes has been synthesised, and the solubility and luminescent properties of these complexes are investigated. Lastly, the applications of these complexes for use in bioconjugation and electrochemiluminescence (ECL) are explored.

  1. 1. Yu, Y.; Zhang, L.-K.; Buevich, A. V.; Li, G.; Tang, H.; Vachal, P.; Colletti, S. L.; Shi, Z.-C., Chemoselective Peptide Modification via Photocatalytic Tryptophan β-Position Conjugation. Journal of the American Chemical Society 2018, 140 (22), 6797-6800.
  2. 2. Rigolot, V.; Simon, C.; Bouchet, A.; Di Battista, V.; Karpov, D.; Vauzeilles, B.; Sliwa, M.; Bohic, S.; Biot, C.; LION, C., Click-ready Iridium(III) complexes as versatile bioimaging probes for bioorthogonal metabolic labeling. ChemRxiv 2024, 2024 (0213).
  3. 3. Schreier, M. R.; Guo, X.; Pfund, B.; Okamoto, Y.; Ward, T. R.; Kerzig, C.; Wenger, O. S., Water-Soluble Tris(cyclometalated) Iridium(III) Complexes for Aqueous Electron and Energy Transfer Photochemistry. Acc. Chem. Res. 2022, 55 (9), 1290-1300.
  4. 4. Manimaran, K. S.; Semjanov, S. K.; White, K. F.; Adcock, J. L.; Doeven, E. H.; Hayne, D. J.; Francis, P. S.; Barnard, P. J., Exploiting a New Strategy to Prepare Water-Soluble Heteroleptic Iridium(III) Complexes to Control Electrochemiluminescence Reaction Pathways in Aqueous Solution. Chemistry – A European Journal 2025, 31 (29), e202500701.