Design and synthesis of a novel tripod rhodamine derivative for trivalent metal ions detection

A tripod rhodamine derivative (L) with flexible chains was synthesized through linking tris(2-aminoethyl)amine appended rhodamine and two thiophene groups. Based on the synergetic action of the acidic medium provided by trivalent metal ions and stability complex came from trivalent metal ions and probe L, the probe displayed higher selectivity and sensitivity in CH3OH/H2O (1/3) solution. The formation of these complexes caused a new absorption peak appearance at 555 nm along with color changes of the solution. Meanwhile, a drive fluorescence behaviors of probe L by the trivalent metal ions were observed with a dramatical enhancement of the fluorescence at 585 nm, respectively. Interestingly, introducing EDTA to the probe L/Fe(III) complex, the fluorescence intensity of the complex was further enhanced. Based on the high throughput analysis strategy, the probe L was designed as a logic gate for detecting trivalent metal ions. Typically, the combination ratio of the probe L with Fe(III) was 1/1 (mole), which was obtained by Job-plot experiment and further confirmed by DFT calculations. Moreover, the tripod rhodamine derivative as a “turn-on” fluorescence switch was applied to detect Fe(III) in actual sample.