Chelation of specific metal ions imparts coplanarity and fluorescence in two imidazo[1,2-a]pyridine derivatives: Potential chemosensors for detection of metal ions in aqueous and biosamples.

Synthesis and chelation induced fluorescence emission from two imidazo[1,2- a ]pyridine derivatives are described. The nonfluorescent molecule 1 containing N and O donor atoms, achieves coplanarity upon interactions with trivalent cations Al3+, Fe3+ and Cr3+, that favors fluorescence emission. Molecule 2 containing two N donor atoms attains coplanarity upon interaction with the only Zn2+ and becomes fluorescent. Both molecules 1 and 2 form a 1:1 complex with interacting metal ions. Other trivalent metal ions (including Bi3+ and In3+) and common divalent metal ions (including Hg2+ and Cd2+) fail to form any complex with 1 or 2 , and they do not interfere in the detection of Zn2+, Al3+, Fe3+ or Cr3+ ions. Noninterference of other metal ions renders 1 and 2 suitable for the detection of fungal cells contaminated with Zn2+, Al3+, Fe3+ or Cr3+ ions. Two structurally related bidentate nonplanar nonfluorescent molecules attain coplanarity through selective interactions with divalent Zn2+ and trivalent Al3+, Fe3+ and Cr3+ ions and emit fluorescence, permitting the detection of these metal ions. Unlabelled Image • Two imidazo[1,2- a ]pyridine based bidentate nonfluorescent molecules 1 and 2 form, respectively, a 1:1 complex with divalent Zn2+ and trivalent Fe3+, Al3+ and Cr3+ ions, adopt coplanar conformation, and show chelation induced fluorescence enhancement. [ABSTRACT FROM AUTHOR]