Imidazole-based chromone Schiff base for highly selective detection of Hg (II) and bio-capability in Caenorhabditis elegans imaging

A new ratiometric fluorescent mercury sensor was proposed based on heterocyclic Schiff's bases obtained by the condensation of 3-formyl chromone with 2-amino benzimidazole its obtained (E)-3-(((1H-benzo[d]imidazol-2-yl)imino)methyl)-4H-chromen-4-one (L3). The sensor L3 exhibits a strong fluorescence at 492 nm with a large Stoke shift of 132 nm in DMSO:H2O (9:1, v/v) due to excited state intra-molecular charge transfer (ESIPT) process but upon interaction with Hg(II) shows blue shift enhanced fluorescence due to produce an LMCT and/or CHEF without any interfering metal ions. The B-H plot and Job's plot studies revealed the estimated association constant (Ka) of 1.424 x 103 M-2 with the formation of a 2:1 stoichiometry complex. The detection limit of sensor L3 was found to be 14.94 x 10-9 M. The L3 sensor was successfully applied for the detection of Hg(II) in the different water samples and bio-capability analysis in Caenorhabditis elegans (Nematode worm). The sensing mechanism was studied by 1H NMR titration, and DFT calculations using the Gaussian 09 program.

Automated summary

A new ratiometric fluorescent sensor for mercury detection was developed using heterocyclic Schiff's bases. The sensor showed strong fluorescence with a large Stoke shift, but upon interaction with Hg(II), the fluorescence was enhanced and blue shifted. The sensor exhibited high sensitivity and selectivity towards Hg(II) in water samples and Caenorhabditis elegans.