Single fluorescein-based probe for selective colorimetric and fluorometric dual sensing of Al3+ and Cu2+

An efficient fluorescein based probe (H 2 L) for the dual sensing of Al 3+ and Cu 2 + has been synthesized and characterized. H 2 L was highly selective toward these two ions with different fluorescence signals and binding modes in two different media. In EtOH-H 2 O (3:2, v/v; pH 4.0), H 2 L selectively binds Al 3+ to form a 1:1 ligand/metal complex, giving rise to a visible pale pink-to-yellow color change and fluorescence enhancement at 440   nm, while in CH 3 CN-H 2 O (2:3, v/v; pH 7.2), H 2 L and Cu 2+ form a 1:2 ratio complex, resulting in a color change from pink to orange-yellow and a significant fluorescence enhancement at 520   nm. The binding modes were confirmed by fluorescence, absorption, IR, ESI-MS and 1 H NMR titrations. The detection limits were calculated to be 7.32   ×   10 −8   M and 1.47   ×   10 −8 M for Al 3+ and Cu 2+ , respectively. Cell imaging studies demonstrate that this sensor is capable of sensing Al 3+ and Cu 2+ in living cells.