Among a series of polyamine-based fluorescent ligands with quinoline of 8-hydroxyquinoline, receptors with lower ability in Zn(ii) or Cd(ii) binding display the highest performance in their optical sensing.

The globally widespread perfluorooctanoic acid (PFOA) is a concerning environmental contaminant, with a possible toxic long-term effects on the environment and human health The development of sensible, rapid, and low-cost detection systems is a current change in modern environmental chemistry. In this context, two triamine-based chemosensors, L1 and L2, containing a fluorescent pyrene unit, and their Zn(II) complexes are proposed as fluorescent probes for the detection of PFOA in aqueous media. Binding studies carried out by means of fluorescence and NMR titrations highlight that protonated forms of the receptors can interact with the carboxylate group of PFOA, thanks to salt bridge formation with the ammonium groups of the aliphatic chain. This interaction induces a decrease in the fluorescence emission of pyrene at neutral and slightly acidic pH values. Similarly, emission quenching has also been observed upon coordination of PFOA by the Zn(II) complexes of the receptors. These results evidence that simple polyamine-based molecular receptors can be employed for the optical recognition of harmful pollutant molecules, such as PFOA, in aqueous media.

Herein, we report on a polyamine receptor L1 bearing pyrene fluorogenic groups for the optical assessment of the non-opioid analgesic drug ketoprofen (KP).

Deferoxamine (DFO) is widely regarded as benchmark chelator for ⁸⁹Zr(IV), a commonly used PET (positron emission tomography) tracer. We have introduced a novel fluorescent coumarin derivative of DFO (DFOKC), characterized by chelating unit and fluorophore covalently linked via a lysine molecule. This design introduces a free primary amine group, which, in perspective, can be functionalized with biological vectors, potentially improving tumor tissue selectivity. Its acid‐base and metal coordination properties toward Cu(II) and Zr(IV) ions were thoroughly characterized using UV‐Vis and fluorescence emission spectroscopy. DFOKC strongly coordinates both metal ions, forming somewhat more stable complexes than DFO, while retaining fluorescence emission, thus enabling dual‐mode optical and PET imaging. Biodistribution assays conducted on NIH‐3T3 fibroblasts, and MDA‐MB‐231 mammary adenocarcinoma cell lines demonstrated that the presence of primary amine groups favors Zr‐DFOKC complex cell internalization via pinocytosis compared to the parent molecule DFOC, in which the fluorophore is linked to the amine group of DFO. Furthermore, crystal violet and MTT assays revealed no cytotoxic effects or mitochondrial impairment, even at concentrations higher than those typically used for radio‐diagnostic applications. These results strongly support the potential of DFOKC as a versatile and promising tool for dual imaging, offering significant advantages in molecular imaging.

Ligands L1 and L2 are composed, respectively, by a diethylenetriamine or a dipropylenetriamine moiety linked at their extremities to anthracene units through methylene bridges and form stable 1:1 complexes with Zn(II), in which the metal is coordinated by all three nitrogens of the ligands. Zn(II) binding by L1 leads to a marked enhancement of the fluorescence emission, thanks to the inhibition of the photoinduced electron transfer (PET) process from the benzylic amine groups of the triamine sub-unit to the excited fluorophore, which normally quenches the emission of fluorescent polyamine receptors. Conversely, the emission of L2 is somewhat quenched by Zn(II) binding likely due—as also indicated by ab initio calculations and molecular dynamics simulations—to the formation of cation π quenching contacts between the metal and the anthracene moieties that overcome the effects of PET inhibition. The Zn(II) complexes of both ligands are able to bind ketoprofen (KP) in its anionic form, thanks to the formation of COO⁻—Zn(II) coordinative bonds, to form [KPZnL]⁺ and [(KP)₂ZnL] (L = L1 or L2) ternary adducts. While KP binding to [ZnL2]²⁺ enhances the fluorophore emission, coordination of KP to [ZnL1]²⁺ slightly reduces the anthracene emission, due, once again, to the formation in the L1 ternary complexes of marked cation π contacts.

Correction for ‘Selective binding and fluorescence sensing of Zn( ii )/Cd( ii ) using macrocyclic tetra-amines with different fluorophores: insights into the design of selective chemosensors for transition metals’ by Giammarco Maria Romano et al. , Dalton Trans. , 2025, https://doi.org/10.1039/d4dt02415j.