Modulating affinities of di-2-picolylamine (DPA)-substituted quinoline sensors for zinc ions by varying pendant ligands.
We have developed a series of di-2-picolylamine (DPA)-substituted quinoline sensors, HQ1- 4, bearing a pendant ligand at the 8 position of quinoline. UV-vis spectra of HQ1- 4 showed similar variations to that of HQ5 but with different varying extents upon the titration of zinc ions. Fluorescence intensities of HQ1, HQ3, and HQ4 were enhanced 4-6 times upon the addition of 1 equiv of zinc ions under an aqueous buffer. Somewhat unexpectedly, HQ2 is nonfluorescent in the presence of metal ions, including zinc ions. The affinities of HQ sensors are distributed in a broad range from nanomolarity to femtomolarity by varying the pendant ligands near the coordination unit. More importantly, these new sensors exhibited very high selectivity for Zn(2+) over Na(+), K(+), Mg(2+), and Ca(2+) at the millimolar level and over other transition metal ions at the micromolar level, except for Cd(2+). These findings indicated that the incorporations of the pendant groups exerted no effect on the spectroscopic properties and selectivity of the parent fluorescent sensor, with the exception of HQ2. Finally, X-ray crystal structures of ZnHQ's revealed that the auxiliary pendant groups at the 8 position participated in zinc coordination and were able to tune the affinities of HQ sensors.
Xue
Lin
L
Beijing National Laboratory for Molecular Sciences, CAS Key Laboratory of Photochemistry, Institute of Chemistry, Chinese Academy of Sciences, Beijing, 100190, People's Republic of China.
Wang
Huan-Huan
HH
Wang
Xiao-Jun
XJ
Jiang
Hua
H
D002412:Cations / Q000737:chemistry; D018360:Crystallography, X-Ray; D006900:Hydroxylation; D008024:Ligands; D008958:Models, Molecular; D015394:Molecular Structure; D010777:Photochemistry; D011725:Pyridines / Q000737:chemistry*; D011804:Quinolines / Q000138:chemical synthesis / Q000737:chemistry*; D015032:Zinc / Q000737:chemistry*
D002412:Cations; D008024:Ligands; D011725:Pyridines; D011804:Quinolines; C037219:quinoline; D015032:Zinc