Al(iii)-responsive "off-on" chemosensor based on rhodamine derivative and its application in cell imaging

In this work, a new rhodamine chemosensor (P) with excellent photochromic properties upon vis irradiation was designed and synthesized. The fabricated chemosensor P could detect Al³⁺ via the opening of the spirolactam ring of the rhodamine unit with high selectivity and sensitivity. The spirolactam ring opening was confirmed by NMR and infrared spectroscopy. Upon binding with Al³⁺, the generated 1 : 1 P-Al³⁺ complex, confirmed by Job's plot titrations and mass spectrometry analysis, could exhibit a remarkable fluorescence enhancement with a limit of detection (LOD) of 0.16 μM. Furthermore, the sensing of P to Al³⁺ in vivo was also studied quantitatively and qualitatively in detail, and the results showed that the coordination between P with Al³⁺ was reversible in living cells.