Iridium complexes are of interest due to their relatively long excited-state lifetime, high photoluminescence efficiency, and excellent color tuning, which makes them useful for solar energy conversion, molecular sensing, and photocatalysis applications.

Mei-Jin Li and colleagues, Fuzhou University, China, have synthesized and characterized water-soluble and biocompatible iridium(III) complexes with appended sugar motifs. Complexes 1 and 2 (see figure) were found to emit strongly at room temperature upon excitation with both UV and visible light in water solution, with emission maxima at ca. 582 and 557 nm, respectively. The luminescence quantum efficiency of complex 2 in water was much higher than the standard, [Ru(bpy)₃]Cl₂, which would make it more sensitive in analytical and bioanalytical applications.

The complexes exhibited very low cytotoxicity on HepG2 cells, and preliminary experiments demonstrated the feasibility of sensing lectin with these iridium(III) complexes.

Images: (c) Wiley-VCH

• Water-Soluble and Biocompatible Cyclometalated Iridium(III) Complexes: Synthesis, Luminescence and Sensing Application
  M.-J. Li, P. Jiao, W. He, C. Yi, C.-W. Li, X. Chen, G.-N. Chen, M. Yang,
  Eur. J. Inorg. Chem. 2011, 197-200.
  DOI: 10.1002/ejic.201000991