Spirolactone and spirothiolactone rhodamine-pyrene probes for detection of Hg2 + with different sensing properties and its application in living cells

Two new rhodamine B-based fluorescent probes PyRbS and PyRbO containing pyrene moiety were designed and synthesized. Both of the probes showed colorimetric and fluorometric sensing abilities for Hg2+ with high selectivity over other metal ions. The binding analysis using Job's plot suggested 1:1 stoichiometry for the complexes formed for Hg2+. Compared with PyRbO, the PyRbS showed higher selectivity and sensitivity due to the thiophilic property of Hg2+ ion. The PyRbS exhibited the linear fluorescence quenching to Hg2+ in the range of 0.3 to 4.8μM (λex=365nm) and 0.3 to 5.4μM (λex=515nm), and the detection limit was 0.72μM. Moreover, ratiometric changes of PyRbS with Hg2+ in absorption spectrum were observed, which could not be obtained in the combination of PyRbO with Hg2+. In addition, the methyl thiazolyl tetrazolium (MTT) assay demonstrated that RbPyS had low cytotoxicity and was successfully used to monitor intracellular Hg2+ levels in living cells.