Selective and sensitive off-on probes specific for palladium detection and their application in biological environments

Two rhodamine B derivatives ROP and ROM have been rationally designed, synthesized and characterized. The probes exhibited highly selective Pd (II) - enhanced absorbance and fluorescence emission above 540 nm in ethanol-water (4/6, v/v, 20 mmol/L HEPES, pH 7.4) by a reversible way. Upon the addition of Pd (II), the rhodamine spirolactam ring was unfolded and a 1:1 metal-ligand was formed, which can be used for “naked-eyes” detection. In addition, cytotoxicity and bioimaging studies by HepG2 living cells and living mice indicated that the probes were negligible cytotoxicity, cell permeable and suitable for detecting Pd (II) in biological environments.