title: A long-lived luminescence and EPR bimodal lanthanide-based probe for free radicals.
abstract: We developed a novel spin-labeled terbium complex Tb(3+)/cs124-DTPA-TEMPO (1) by covalently labeling a nitroxide radical on the terbium complex for monitoring free radicals of various areas. This lanthanide complex probe shows a high EPR signal which resulted from the nitroxide radical moiety, and is weakly luminescent which resulted from the intramolecular quenching effect of the nitroxide radical on sensitised terbium luminescence. The intensity of both the EPR and luminescence can be modulated by eliminating the paramagnetism of the nitroxide radical through recognition of a carbon-centered radical analyte and thus gives a quantification of the analyte. We have preliminarily applied this probe in the luminescent detection of model carbon-centered radicals and hydroxyl radicals (·OH). This probe is water-soluble and contains lanthanide-luminescence properties, favorable for the time-resolved luminescence technique. The investigation of the intramolecular quenching process has showed that the labeled nitroxide radical quenches multiple excited states of the terbium complex, resulting in highly efficient quenching of terbium luminescence. This probe is the first example of intramolecular modulation of lanthanide luminescence by a nitroxide radical.
authors.affiliation: The Key Laboratory for Chemical Biology of Fujian Province, Department of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, China.
authors.forename: Jinqing
authors.initials: J
authors.lastname: Hong
authors.forename: Yuanming
authors.initials: Y
authors.lastname: Zhuang
authors.forename: Xiang
authors.initials: X
authors.lastname: Ji
authors.forename: Xiangqun
authors.initials: X
authors.lastname: Guo
mesh_terms: D056831:Coordination Complexes / Q000138:chemical synthesis / Q000737:chemistry; D003497:Cyclic N-Oxides / Q000737:chemistry; D004578:Electron Spin Resonance Spectroscopy / Q000379:methods*; D005609:Free Radicals / Q000737:chemistry*; D017665:Hydroxyl Radical / Q000737:chemistry; D008163:Luminescent Measurements / Q000379:methods*; D009569:Nitric Oxide / Q000737:chemistry; D004369:Pentetic Acid / Q000737:chemistry; D013113:Spin Labels; D013725:Terbium / Q000737:chemistry*
chemical_list: D056831:Coordination Complexes; D003497:Cyclic N-Oxides; D005609:Free Radicals; D013113:Spin Labels; D013725:Terbium; D009569:Nitric Oxide; D017665:Hydroxyl Radical; D004369:Pentetic Acid; C003959:TEMPO