A novel dual channel six-membered spirorhodamine for Cu2+ and ClO- depending on solvent and application in real samples and bioimaging

To reveal the solvent dependence of six-membered rhodamine spirocycles (SMRS), a new probe SM-RB has been synthesized and investigated the spectral properties in different solvents upon the addition of various metal ions and anions. SM-RB exhibited high selectivity for Cu2+ in CH3CN/HEPES and ClO- in C2H5OH/HEPES solutions, respectively. The spectral changes of SM-RB in the presence of ClO- in C2H5OH/HEPES solution were much less than that of Cu2+ in CH3CN/HEPES. The detection limit of Cu2+ was as low as 36 nM (fl) in CH3CN/HEPES. The kinetic equilibration time (8 s) indicated that the two solvent systems did not delay the spectral response speed to Cu2+ and ClO-. Solvent systems influenced the pKa value of SM-RB in CH3CN/HEPES and C2H5OH/HEPES. The pKa value of SM-RB was 4.34 (±0.7) (Abs) and 4.75 (±0.14) (Fl) in CH3CN/H2O, but can’t be exactly calculated by pH titration in C2H5OH/H2O. The reversibility and Job plot of SM-RB were investigated to propose the response mechanism of SM-RB with Cu2+ and ClO- in the two solvent systems. Finally, SM-RB not only can be used for the quantitative detection of copper ions in grape peel, but also can real-time monitor the fluctuation of Cu2+ in lysosomal pools.