Specific recognition of Cr3+ under physiological conditions by allyl substituted appendage rhodamine and its cell-imaging studies

An allyloxynitrophenylimio-propylhydroxyl appended rhodamine (RD-3) specifically recognises Cr3+ in aqueous buffer medium at pH 7.4. The visible light excitable reagent (lambda(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 similar 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 H-1 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.