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A europium(III) complex as an efficient singlet oxygen luminescence probe

Abstract:

A new europium(III) complex, [4′-(10-methyl-9-anthryl)-2,2′: 6′2″-terpyridine-6,6″-diyl]bis(methylenenitrilo) tetrakis(acetate)-Eu3+, was designed and synthesized as a highly sensitive and selective time-gated luminescence probe for singlet oxygen ( 1O2). The new probe is highly water soluble with a large stability constant of ∼1021 and a wide pH available range (pH 3-10), and can specifically react with 1O2 to form its endoperoxide (EP-MTTA-Eu3+) with a high reaction rate constant at 1010 M-1 s-1, accompanied by the remarkable increases of luminescence quantum yield from 0.90% to 13.8% and lifetime from 0.80 to 1.29 ms, respectively. The wide applicability of the probe was demonstrated by detection of 1O2 generated from a MoO 42-/H2O2 system, a photosensitization system of 5, 10, 15, 20-tetrakis(1-methyl-4-pyridinio) porphyrin tetra(p-toluenesulfonate) (TMPyP), and a horseradish peroxidase catalyzed aerobic oxidation system of indole-3-acetic acid (IAA). In addition, it was found that the new probe could be easily transferred into living HeLa cells by incubation with TMPyP. A time-gated luminescence imaging technique that can fully eliminate the short-lived background fluorescence from TMPyP and cell components has been successfully developed for monitoring the time-dependent generation of 1O2 in living cells. © 2006 American Chemical Society.