Dual-Emissive Cyclometalated Iridium(III) Polypyridine Complexes as Ratiometric Biological Probes and Organelle-Selective Bioimaging Reagents

Kenneth Yin Zhang*, Hua Wei Liu, Man Chung Tang, Alex Wing Tat Choi, Nianyong ZHU, Xi Guang Wei, Kai Chung Lau, Kenneth Kam Wing Lo

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

74 Citations (Scopus)

Abstract

In this Article, we present a series of cyclometalated iridium(III) polypyridine complexes of the formula [Ir(N^C)2(N^N)](PF6) that showed dual emission under ambient conditions. The structures of the cyclometalating and diimine ligands were changed systematically to investigate the effects of the substituents on the dual-emission properties of the complexes. On the basis of the photophysical data, the high-energy (HE) and low-energy (LE) emission features of the complexes were assigned to triplet intraligand (3IL) and triplet charge-transfer (3CT) excited states, respectively. Time-dependent density functional theory (TD-DFT) calculations supported these assignments and indicated that the dual emission resulted from the interruption of the communication between the higher-lying 3IL and the lower-lying 3CT states by a triplet amine-to-ligand charge-transfer (3NLCT) state. Also, the avidin-binding properties of the biotin complexes were studied by emission titrations, and the results showed that the dual-emissive complexes can be utilized as ratiometric probes for avidin. Additionally, all the complexes exhibited efficient cellular uptake by live HeLa cells. The MTT and Annexin V assays confirmed that no cell death and early apoptosis occurred during the cell imaging experiments. Interestingly, laser-scanning confocal microscopy revealed that the complexes were selectively localized on the cell membrane, mitochondria, or both, depending on the nature of the substituents of the ligands. The results of this work will contribute to the future development of dual-emissive transition metal complexes as ratiometric probes and organelle-selective bioimaging reagents. (Figure Presented).

Original languageEnglish
Pages (from-to)6582-6593
Number of pages12
JournalInorganic Chemistry
Volume54
Issue number13
DOIs
Publication statusPublished - 6 Jul 2015

Scopus Subject Areas

  • Physical and Theoretical Chemistry
  • Inorganic Chemistry

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