Monitoring inorganic pyrophosphatase activity with the fluorescent dizinc(ii) complex of a macrocycle bearing one dansylamidoethyl antenna

Selective sensing of PPi by fluorogenic Al(III)-probe complex in aqueous medium

A newly designed Schiff base probe JN has been synthesized. It is highly selective and sensitive towards Al³⁺ in nearly 100% aqueous medium by exhibiting a dramatic "turn-on" fluorescence response at 495 nm (λ_ex = 450 nm). The sensing mechanism of JN towards Al³⁺ ions was proposed as the combination of PET, ICT, ESIPT, and CHEF processes according to spectra studies and theory calculations. The in situ generated mononuclear Al(III) complex JN-Al³⁺ could sequentially detect PPi ions by turn-off fluorescence response. The selectivity and sensitivity of the JN-Al³⁺ complex towards PPi ions are based on demetalization process. Interestingly, the fact that Al³⁺ can bind with 1, 2, or 3 PPi has been revealed by HRMS study. The probes JN and JN-Al³⁺ complexes were able to capture Al³⁺ and PPi ions, respectively, as demonstrated by fluorescence imaging of the adult zebrafish and onion inner epidermal cells samples.

Selective Coordination of Cu2+ and Subsequent Anion Detection Based on a Naphthalimide-Triazine-(DPA)2 Chemosensor

A new fluorescent chemosensor for copper (II) and subsequent anion sensing was designed and fully characterized. The sensor consisted of a 1,8-naphthalimide core, bearing two terminal dipicolylamine (DPA) receptor units for binding metal cations, and an ethoxyethanol moiety for enhanced water solubility. The DPA units are connected to position 4 of the fluorophore via a triazine-ethylenediamine spacer. Fluorescence titration studies of the chemosensor revealed a high selectivity for Cu²⁺ over other divalent ions, the emissions were strongly quenched upon binding, and a stability constant of 5.52 log units was obtained. Given the distance from DPA chelating units and the fluorophore, quenching from the Cu²⁺ complexation suggests an electron transfer or an electronic energy transfer mechanism. Furthermore, the Cu²⁺-sensor complex proved to be capable of sensing anionic phosphate derivatives through the displacement of the Cu²⁺ cation, which translated into a full recovery of the luminescence from the naphthalimide. Super-resolution fluorescence microscopy studies performed in HeLa cells showed there was a high intracellular uptake of the chemosensor. Incubation in Cu²⁺ spiked media revealed a strong fluorescent signal from mitochondria and cell membranes, which is consistent with a high concentration of ATP at these intracellular sites.