A thiophene-rhodamine dyad as fluorescence probe for ferric ion and its application in living cells imaging

A thiophene-rhodamine dyad (BYY) was easily synthesized as a fluorescence probe from 2-thiopheneacetic acid and N-(rhodamine-B)lactam-ethylenediamine. The probe showed high response speed and sensitivity toward Fe3+ in ethanol/water (2/3, v/v, pH = 7.2), and the limit of detection was as low as 10−7 M. From the Job's plot, mass spectrum, 1H NMR spectra and the theoretical calculation, the 1:2 complex ratio of Fe3+-probe was obtained and the response mechanism was determined. Significantly, the reversible binding of BYY to Fe3+ was achieved through the strong Fe3+ affinity of Na4P2O7, and the probe showed well antijamming abilities in the presence of common metal ions. Moreover, the probe was cell-permeable and could sensitively response to Fe3+ in living cells with satisfying resolution.