Synthesis and time-resolved fluorimetric application of a europium chelate-based phosphorescence probe specific for singlet oxygen

Abstract

A new europium chelate, [4'-(9-anthryl)- 2,2': 6',2 ''-terpyridine-6,6 ''-diyl] bis( methylenenitrilo) tetrakis( acetate)Eu3+ (ATTA-Eu3+), has been designed and synthesized as a highly sensitive and selective time-resolved phosphorescence probe for singlet oxygen ( O-1(2)). The probe can specifically react with O-1(2) to yield its endoperoxide (EP-ATTA-Eu3+) with a great increase of the luminescence quantum yield and a long phosphorescence lifetime of 1.21 ms, which renders the probe favorable to be used for highly sensitive time-resolved luminescence detection of O-1(2). The new phosphorescence probe is highly water soluble with a large stability constant of similar to 10(20) and a wide available pH range at pH > 3. Upon reactions with some reactive oxygen species including hydrogen peroxide, superoxide, hydroxyl radical and O-1(2), the probe shows high specificity for O-1(2). The probe was used for quantitative detection of O-1(2) generated from a MoO42--H2O2 system to give a detection limit of 2.8 nM. Furthermore, the good applicability of the probe was demonstrated by the real-time monitoring of the kinetic process of O-1(2) generation in a horseradish peroxidase (HRP) catalyzed oxidation system of indole-3-acetic acid (IAA) in a weakly acidic buffer and in a photosensitization system of 5,10,15,20-tetrakis(N-methyl-4-pyridyl)-21H, 23H-porphine (TMPyP) in a neutral buffer.