Rhodamine hydrazone derivatives bearing thiophene group as fluorescent chemosensors for Hg²⁺

Rhodamine derivatives bearing the thiophene (1) and bisthiophene (2) groups are synthesized and their binding selectivity toward various metal ions was studied. The X-ray crystal structure of 1 was also reported. Probes 1 and 2 showed highly selective "Off-On" fluorescence changes with Hg ²⁺ among various metal ions. These selective changes were attributed to the spirolactam ring opening processes and subsequent hydrolysis. Probes 1 and 2 were sucessfully applied to the cell-imaging of Hg²⁺ using HeLa cells.