A mitochondria-specific visible-light sensitized europium β-diketonate complex with red emission

Our recently developed Eu3+ coordination compound, Eu(pfppd)(3)(tpy) [where Hpfppd = 4,4,5,5,5-pentafluoro-3-hydroxy-1-(phenanthren-3-yl) pentanedione and tpy = 2,2':6,6 ''-terpyridine] exhibits significant quantum yield (Phi(overall) = 41%) and long D-5(0) lifetime (880 mu s) values under biologically relevant pH conditions (pH = 7.4) when excited with visible light. Hence, the Eu3+ luminescent complex was examined for live cell imaging using the rat embryonic heart cell line, H9c2. The ternary Eu3+ complex permeates into the H9c2 cells and co-localises with the mitochondria, as demonstrated by counterstaining experiments. Furthermore, the designed Eu3+ bioprobe remains undissociated in the cell medium, showed a good cell permeability and a fast cellular uptake with a specific localization profile. Thus it has the potential to become a time-resolved imaging probe that is excitable in the visible-light range.