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

Our recently developed Eu(3+) 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 (Φoverall = 41%) and long (5)D0 lifetime (880 μs) values under biologically relevant pH conditions (pH = 7.4) when excited with visible light. Hence, the Eu(3+) luminescent complex was examined for live cell imaging using the rat embryonic heart cell line, H9c2. The ternary Eu(3+) complex permeates into the H9c2 cells and co-localises with the mitochondria, as demonstrated by counterstaining experiments. Furthermore, the designed Eu(3+) 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.