Rhodamine hydrazone derivatives based selective fluorescent and colorimetric chemodosimeters for Hg²⁺ and selective colorimetric chemosensor for Cu²⁺

In this paper, we report new rhodamine hydrazone derivatives bearing multiple ether units or phenol group as selective fluorescent and colorimetric chemodosimeters for Hg²⁺ and a selective colorimetric chemosensor for Cu²⁺. Monomeric derivative 1 containing additional ether moieties and a dimeric system 2 displayed excellent fluorescence and colorimetric selectivity for Hg²⁺ in aqueous solution. 1 displayed much lower detection limit compared to 2 and both of these new hydrazone derivatives act as chemodosimeters for Hg²⁺. On the other hand, dimeric system 3 containing an additional phenol group showed a highly selective and reversible colorimetric change with Cu²⁺ in CH₃CN-HEPES buffer. The detection limit was calculated as 0.15 μM with the linear range of 280-800 nM. Finally, probe 1 was further applied to the cell-imaging of Hg²⁺ using HeLa cells.