A near-infrared colorimetric and fluorometric chemodosimeter for Cu2+ based on a bis-spirocyclic rhodamine and its application in imagings

A new bis-spirocyclic rhodamine B derivative was developed as a near-infrared colorimetric and “turn-on” fluorometric chemodosimeter ( 1 ) with a large Stokes shift (70 nm) for Cu 2+ . In response to Cu 2+ , the solution of 1 displayed major absorption at 700 nm, from colorless to blue within ten seconds. At the same time, emissions at 580 nm (excitation at 520 nm) and at 770 nm (excitation at 650 nm) were turned on. Good linear relationships between absorbance at 700 nm, fluorescence at 580 and 770 nm and concentration of Cu 2+ in wide ranges were obtained in both colorimetric and fluorometric analyses, with the detection limits of 0.57 μM, 9 nM and 28 nM, respectively. Irreversible ring-opening processes of 1 coordinated with Cu 2+ , followed by hydrolysis as well as acylated reaction were proposed. Furthermore, 1 was applied to image Cu 2+ in HepG2 living cells and within the mitochondria of the cells in the roots of paulownia sprouts.