Red-emitting heteroleptic iridium(III) complexes: photophysical and cell labeling study

Author(s)

Canisares, Felipe S. M. ; Mutti, Alessandra M. G. ; Santana, Edy F. ; Oliveira, Vytor C. ; Cavalcante, Dalita G. S. M. ; Job, Aldo E. ; Pires, Ana M. ; Lima, Sergio A. M.

• Document type: Journal article
• Source: PHOTOCHEMICAL & PHOTOBIOLOGICAL SCIENCES; v. 21, n. 6, p. 14-pg., 2022-03-18.

Abstract

Two red-emitting heteroleptic iridium(III) complexes (Ir-p and Ir-q) were synthesized and their photophysical and biological properties were analyzed. After their structures have been confirmed by several techniques, such as H-1 NMR, C-13 NMR, FT-IR, UV-Vis, and MALDI TOF analyses, their luminescence behavior was investigated in ethanol and PBS (physiological medium, pH similar to 7.4) solutions. Emission spectra of both complexes are dominated by (MLCT)-M-3 states at room temperature in ethanolic solution, but at 77 K the Ir-q exhibits the (LC)-L-3 as the dominant emission state. The Ir-q complex shows one of the highest emission quantum yields, 11.5%, for a red emitter based on iridium(III) complexes in aerated PBS solution, with color coordinates (x;y) of (0.712;0.286). Moreover, both complexes display high potential to be used as a biological marker with excitation wavelengths above 400 nm, high water solubility (Ir-p 1838 mu mol L-1, Ir-q 7601 mu mol L-1), and distinct emission wavelengths from the biological autofluorescence. Their cytotoxicity was analyzed in CHO-k1 cells by MTT assays, and the IC50 was estimated as being higher than 131 mu mol L-1 for Ir-p, and higher than 116 mu mol L-1 for Ir-q. Concentrations above 70% of viability were used to perform cell imaging by confocal and fluorescence microscopies and the results suggest that the complexes were internalized by the cell membrane and they are staining the cytoplasm region. (AU)

• FAPESP's process: 15/03400-5 - Synthesis and characterization of lanthanide complexes with carboxylic acid ligands
• Grantee: Felipe da Silva Manrique Canisares
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• FAPESP's process: 19/26103-7 - Silica particles decorated with luminescent complexes for application in sensors and cellular imaging
• Grantee: Sergio Antonio Marques de Lima
• Support Opportunities: Regular Research Grants