Specific recognition of Cr³⁺ under physiological conditions by allyl substituted appendage rhodamine and its...

An allyloxynitrophenylimio-propylhydroxyl appended rhodamine (RD-3) specifically recognises Cr³⁺ in aqueous buffer medium at pH 7.4. The visible light excitable reagent (λ_ex 505 nm) on selective binding to Cr³⁺ exhibited a strong fluorescence turn-on response with powerful emission at 557 nm and the tail of this luminescence band is extended to ∼650 nm. Interference studies confirm that other metal ions (27 ions) do not hamper the detection process of Cr³⁺. The sensing mechanism is studied by absorption, fluorescence, Job's plot, and ¹H NMR titration studies. The detection limit is as low as 33 nM. The practical applicability of RD-3 is examined for imaging Cr(iii) ions in HCT116 (human colorectal carcinoma) cells.