Modulating affinities of di-2-picolylamine (DPA)-substituted quinoline sensors for zinc ions by varying pendant ligands

Inorg Chem. 2008 May 19;47(10):4310-8. doi: 10.1021/ic702393z. Epub 2008 Apr 15.


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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cations / chemistry
  • Crystallography, X-Ray
  • Hydroxylation
  • Ligands
  • Models, Molecular
  • Molecular Structure
  • Photochemistry
  • Pyridines / chemistry*
  • Quinolines / chemical synthesis
  • Quinolines / chemistry*
  • Zinc / chemistry*


  • Cations
  • Ligands
  • Pyridines
  • Quinolines
  • quinoline
  • Zinc