Anthraquinone-based Schiff base fluorescent probe for the sequential sensing of Al3+ and pyrophosphate in a near-perfect aqueous solution and bioimaging

A new anthraquinone derivative fluorescent probe (DPHA) was designed and synthesized for sequentially detecting aluminum ions and pyrophosphate (PPi) in a near-perfect aqueous medium with 0.4 % DMSO as a co-solvent. The DPHA probe displayed “turn-on” fluorescence sensing of Al 3+ at 575 nm, overcoming the interference of the other common cations through an apparent color variation from purple to light pink. Anthraquinone-derived conjugated skeleton and Schiff base-mediated multiple binding sites were responsible for the sensitive fluorescence response and selective recognition, respectively, thus producing a chelation-enhanced fluorescence effect. Furthermore, Job's plot analysis and high-resolution mass spectrometry (HRMS) studies supported the formation of a 1:1 ligand/metal complex for Al 3+ . The plausible binding mechanism was recognized by both experimentally and theoretically. The succeeding addition of PPi regenerated the original spectrum of DPHA and thus the strong affinity of Al 3+ to PPi. The in-situ formed DPHA-Al 3+ complex for selective identification of PPi by electrostatic interaction by drawing out Al 3+ and releasing the DPHA probe. Except for specific recognition of Al 3+ and PPi with corresponding low detection limits of 42.2 nM and 65.2 nM (S/N = 3). Owing to its good biocompatibility, DPHA also applied as a visual probe for monitoring Al 3+ ions and PPi in living cells and zebrafish, demonstrating its outstanding potential in biological work.