A coumarin based fluorescent probe enabling nanomolar detection of Zn2+ and Cu2+

A rationally designed fluorescent probe constructed on a coumarin platform (R-1) distinguished sequentially & distinctly two vital ions viz. Zn2+ and Cu2+ through different mechanistic approaches at their nanomolar con-centrations. The native dark state (off-state) of R-1 was illuminated (on-state) upon its interaction with Zn2+ and further reverted back to its natural dark state in the presence of Cu2+ in aqueous medium. The structural details of R-1 and its ensemble with Zn2+ were unambiguously elucidated through their single-crystal XRD studies. The single crystals of R-1-Zn2+ with chloride and acetate counter anions displayed a fascinating 1-D co-ordination polymeric supramolecular structures. The strategic incorporation of pyridine -N in R-1 introduced a yet another binding site and consequently modulated its optical characteristics, while the analogous derivative R-3, inspite of having electron withdrawing -NO2 group, (instead of pyridine -N as in R-1 and R-2) was unable to produce any significant sensing response under similar conditions. The corresponding optical responses with Zn2+/Cu2+ were equated with INHIBIT logic-gate function. Moreover, the R-1 was deployed for imaging the above ionic analytes in rat glioblastoma cell lines (c6) through confocal laser scanning microscopy.