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Phosphorescent Zinc Probe for Reversible Turn-On Detection with Bathochromically Shifted Emission

Title
Phosphorescent Zinc Probe for Reversible Turn-On Detection with Bathochromically Shifted Emission
Authors
Ryu, Seung YeonHuh, MijoungYou, YoungminNam, Wonwoo
Ewha Authors
남원우유영민
SCOPUS Author ID
남원우scopus; 유영민scopus
Issue Date
2015
Journal Title
INORGANIC CHEMISTRY
ISSN
0020-1669JCR Link1520-510XJCR Link
Citation
vol. 54, no. 20, pp. 9704 - 9714
Publisher
AMER CHEMICAL SOC
Indexed
SCI; SCIE; SCOPUS WOS scopus
Abstract
Phosphorescent molecules are attractive complements to fluorescent compounds for bioimaging. Time-gated acquisition of the long-lived phosphorescence signals provides an effective means to eliminate unwanted background noises due to short-lived autofluorescence. We have previously investigated the molecular principles governing modulation of photoinduced electron transfer in phosphorescence zinc probes that were based on biscyclometalated Ir(III) complexes (Woo, H. et al. J. Am. Chem. Soc. 2013, 135, 4771-4787). The studies established that phosphorescence turn-on responses would be attainable for Ir(III) complexes with high triplet-state energies. This sets an upper limit to an emission wavelength, restricting the development of red- or near-IR-phosphorescence turn-on probes. To address this challenge, we designed and synthesized a new phosphorescent probe having an electron-deficient 2-(2-pyridyl)pyrazine diimine ligand tethering a di(2-picolyl)amine (DPA) zinc receptor. This ligand control led to red phosphorescence emission (lambda(ems) = 596 nm), with an excited-state reduction potential (E*(red)) retained as high as 1.44 V versus standard calomel electrode (SCE). The E*(red) value was more positive than the ground-state oxidation potential of DPA (1.05 V vs SCE), permitting an occurrence of photoinduced electron transfer at a rate of 2 x 10(7) s(-1). Zinc binding at DPA abolished the electron transfer to produce phosphorescence turn-on signaling. The probe was capable of detecting zinc ions selectively over other competing biological metal ions in aqueous buffer solutions (pH 7.4, 20 mM piperazine-N,N'-bis(2-ethanesulfonic aid)) with the zinc dissociation constant of 109 pM. Finally, bioimaging utility of the probe has been successfully demonstrated by visualizing exogenously supplied zinc ions in live HeLa cells. The research described in this paper demonstrates that judicious ligand control enables retention of turn-on responses in the low-energy phosphorescence region.
DOI
10.1021/acs.inorgchem.5b00967
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자연과학대학 > 화학·나노과학전공 > Journal papers
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