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Selective binding and optical sensing of Zn(II) and Cd(II) by L1, HL2, L3, H2L4 and H2L5 receptors were analysed in aqueous solutions by coupling potentiometric, UV-vis absorption and fluorescence emission measurements, with the aim to determine the effect of complex stability on selective signalling of metals with similar electronic configurations. All receptors share the same cyclic tetra-amine binding unit attached to a single quinoline (Q) or 8-hydroxyquinoline (8-OHQ) unit (L1 and HL2, respectively), two Q or 8-OHQ moieties (L3 and H2L4, respectively), and, finally, two Q and two acetate groups (H2L5). The crystal structures of the Cd(II) and Zn(II) complexes show that L3 and H2L4 feature a cavity in which the larger Cd(II) complex is better fitted than the Zn(II) complex, leading to the formation of more stable Cd(II) complexes. In turn, Zn(II) forms more stable complexes with L1 and HL2, owing to its high tendency to give 5-coordinated complexes. Considering optical selectivity, Zn(II) gives the most emissive complex with L3, while the corresponding Cd(II) complex is basically quenched. The gathered structure of the Zn(II) complex, in which the two Q units are associated with one another—a structural motif not observed in the [CdL3]2+ complex—leads to poor solvation of the Q units, favouring complex emission. Among 8-OHQ-containing receptors, the most emissive complex is formed by Cd(II) with HL2, containing a single 8-OHQ moiety. H2L4 forms non-emissive complexes: the presence of two coordinating 8-OHQ moieties weakens metal interactions with the tetra-amine unit, favouring PET to the excited fluorophore that quench the emission. [ABSTRACT FROM AUTHOR]

A multi-analytical approach was used to comprehensively characterize the acid-base, thermal, and surface properties of agri-food processing wastes (i.e., original and pre-treated bergamot, grape and olive pomaces). These biomasses, often underutilised and inadequately studied in terms of their physicochemical properties, were investigated under varying ionic strength conditions at t = 25 °C. This investigation uniquely integrates multiple advanced techniques: Brunauer–Emmett–Teller porosimetry, Scanning Electron Microscopy, Thermogravimetric Analysis coupled with Fourier Transform Infrared Spectroscopy, Differential Scanning Calorimetry, Attenuated Total Reflectance Fourier-Transform Infrared, and potentiometry to provide a holistic understanding of these biomasses potential for environmental remediation. The modelling of ionic strength-dependent acid-base behaviour, established using an extended Debye–Hückel-type equation, revealed the dominant role of carboxylic groups as active sites across all pomace types, although with variations in abundances across the different samples. Additionally, morphological analysis highlighted the presence of irregularly shaped particles, heterogeneous size distributions, and distinct thermal stability trends, with grape pomace exhibiting the highest mass loss. These findings underscore the significant potential of these biomasses for the remediation of cationic pollutants from natural waters. Moreover, this comprehensive characterisation not only advances the understanding of agri-food waste valorisation but also provides a robust framework for designing targeted strategies in environmental applications. [ABSTRACT FROM AUTHOR]

A new palladium(II) complex containing the previously synthesized 4,10-bis[(3-hydroxy-4-pyron-2-yl)methyl]-1,7-dimethyl-1,4,7,10-tetraazacyclododecane ligand maltonis was prepared and characterized both in solution and in the solid state. Hirshfeld surface and energy framework analyses were also performed. Because maltonis already showed antineoplastic activity, the complexation of Pd(II), chosen as an alternative to Pt(II), was investigated to study its possible biological activity. UV-vis and NMR studies confirmed the formation and stability of the complex in aqueous solution at physiological pH. X-ray diffraction data revealed a structure where the Pd(II) ion is lodged in the dimethyl-cyclen cavity, with maltol rings facing each other (closed shape) even if they are not involved in the coordination. DFT analysis was performed in order to understand the most stable shape of the complex. In view of evaluating its possible bioactive conformation, the DFT study suggested a slight energetic preference for the closed one. The resulting closed complex was stabilized in the X-ray structure by intermolecular interactions that replace the intramolecular interactions present in the optimized complex. According to the DFT calculated formation energies, notwithstanding its rarity, the Pd(II) complex of maltonis is the thermodynamically preferred one among analogous complexes containing different metal ions (Pt(II), Co(II), and Cu(II)). Finally, to study its possible biological activity, the interaction between the Pd(II) complex of maltonis and nucleosides was evaluated through NMR and DFT calculations, revealing a possible interaction with purines via the maltol moieties. [ABSTRACT FROM AUTHOR]

In this work, the study of the new ligand 3,3′-bis[N,N-bis(pyridine-2-ylmethyl)aminomethyl]-2,2′-dihydroxybiphenyl (L) is reported, where a central 2,2′-biphenol (BPH) fluorophore was functionalized at 3,3′-positions with two dipicolylamine (DPA) side arms as receptor units. Following the synthesis and full chemical–physical characterization, the acid–base and Zn2+-coordination abilities of L were investigated through a combination of potentiometric, UV-Vis, fluorescence, NMR, XRD and DFT measurements. The optical properties of the ligand turned out to be strongly dependent on the pH, being straightforwardly associated with the protonation state of the BPH moiety, whereas its peculiar design allowed to form stable mono and dinuclear Zn2+ complexes. In the latter species, the presence of two Zn2+ ions coordinatively unsaturated and placed at close distance to each other, prompted us to test their usefulness as metallo-receptors for two environmental pollutants of great relevance, ibuprofen and ketoprofen. Potentiometric and fluorescence investigations evidenced that these important non-steroidal anti-inflammatory drugs (NSAIDs) are effectively coordinated by the metallo-receptors and, of relevance, both the stability and the fluorescence properties of the resulting ternary adducts are markedly affected by the different chemical architectures of the two substrates. This study aims at highlighting the promising perspectives arising from the use of polyamino phenolic ligands as chemosensors for H+/Zn2+ and other additional anionic targets in their metal-complexed forms. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

A new series of ligands containing the 2‐(2‐hydroxy‐3‐ naphthyl)‐4‐methylbenzoxazole (HNBO) fluorophore showed selectivity for Mg2+ ions, without the interference of Ca2+. The most promising representative L3 resulted the best performing sensor for Mg2+ both in solution and embedded in an all‐solid‐state optode, especially towards real samples of drinkable water. [ABSTRACT FROM AUTHOR]

Background: Benzoxazole-containing ligands find many applications both in medicinal chemistry, catalysis and fluorescence chemosensing. Benzoxazole-containing macrocycles could be therefore a good strategy to achieve stable and selective fluorescent complexes with suitable metal ions. In this work, the synthesis, binding, and photochemical properties of a new fluorescent ligand (L) are reported. L is a cyclophane macrocycle containing the 1,3-bis(benzo[d]oxazol-2-yl)phenyl (BBzB) fluorophore and an aliphatic tetra-amine chain to form the macrocyclic skeleton. Methods: Spectrophotometric and spectrofluorimetric measurements, 1H NMR analysis, and DFT calculations were performed. Results: L behaves as a PET-mediated chemosensor, being emissive at 390 nm at acidic pH and non-emissive at basic pH. The chemosensor is able to detect Zn2+ and Cd2+ in an aqueous medium (acetonitrile–water, 4:1 v/v) at neutral pH through a CHEF effect upon metal ion coordination. Paramagnetic metal ions (Cu2+) and heavy atoms (Pb2+, Hg2+) resulted in a quenching of fluorescence or very low emission. Conclusions: The new cyclophane macrocycle L was revealed to be a selective PET-regulated chemosensor for Zn2+ and Cd2+ in an aqueous medium, being able to bind up to two and one metal cations, respectively. The molecule showed a shifted emission towards the visible region compared to similar systems, suggesting a co-planar conformation of the aromatic fragment upon metal coordination. All these data are supported by both experimental measurements and theoretical calculations. [ABSTRACT FROM AUTHOR]

The synthesis and characterization of a novel bis‐urea‐based cage receptor for anions (3S,15S)‐3,15,20,25‐tetramethyl‐1,4,6,12,14,17,20,25‐octaazatricyclo[15.5.5.17.11]octacosa‐7(28),10‐diene‐2,5,13,16‐tetraone (L) is reported. L is a macro‐bicyclic ligand built on the 1,7‐dimethyl‐1,4,7,10‐tetraazacyclododecane scaffold to obtain a cage topology in which two ureido moieties have been inserted as binding sites for anions. L can interact with anion guests (G) via H‐bonding; in particular, it binds both spherical (Cl−) and V‐shaped anions (AcO−) as well as more complex carboxylate anions, such as the norfloxacin (Nor−). NMR experiments highlight that the interaction between L and G mainly occurs at the ureido moieties. L forms L‐G adducts of 1 : 1 ([LG]−) and 1 : 2 ([LG2]2−) stoichiometry with Cl− and AcO−. Otherwise, in the case of Nor− only the formation of the [LG]− complex is observed. L shows higher formation constants values for [LAcO]− (2.9) and [LNor]− (3.6) than [LCl]− suggesting a stronger interaction with the carboxylate anions. In the solid state, three crystal structures of the HL⋅G species were obtained (G=Cl−, AcO−, ClO4−) highlighting the H‐bonding interaction between the chloride, acetate or perchlorate anions and the −NH functions of the ureido fragment. The comparison between the two parent open chain receptors (Lb‐c) and L has been reported and discussed. [ABSTRACT FROM AUTHOR]

The synthesis, solution studies, photochemical properties and the X-ray structure of a chromone based fluorescent PdII complex are reported. The ligand contains two chromone units linked as side arms to an ethylenediamine moiety; in the PdII complex the metal ion preorganizes the two hydroxychromone units forming a rigid structure with a negatively charged pocket formed by four oxygen atoms that is able to interact with hard metal cations, such as ions, giving rise to stable bimetallic complexes. Upon interaction with LaIII and GdIII, in particular, the emission intensity at 423 nm increases by a factor of 2 and 8, respectively, while the other rare earth ions quench the fluorescence. Spectrofluorimetric studies on real matrices showed the possibility to use this system as a selective fluorescence probe to detect and trace the presence of Gadolinium in environmental water acting as an OFF–ON chemosensor, with a LOD of 0.4 ppm and a LOQ of 1.2 ppm. [ABSTRACT FROM AUTHOR]

Herein we describe the synthesis and coordination properties in solution towards Zn2+ and Cd2+ of the ligands L1 and L2 containing the 2,8-dithia-5-aza-2,6-pyridinophane (L) macrocyclic receptor unit and the 2-(2′-hydroxy-3′-naphthyl)-4-methylbenzoxazole (HNBO) or 7-(2-ethylamino)-4-methylcoumarin chromophores. Spectrophotometric and spectrofluorimetric measurements in the UV-visible region (MeCN/H2O solution 4 : 1 v/v) and 1H NMR measurements provided insight into the nature of complex species and transduction mechanisms responsible for the optical responses. The ligands showed an OFF–ON response upon addition of Zn2+ and Cd2+, for L1, and only Cd2+, for L2, in both cases attributable to the formation of 1 : 1 metal-to-ligand complexes. The crystal structure of [CdL2(NO3)2] is reported, Cd2+ being heptacoordinated by L and NO3− anions in a N2S2O3 environment. Exploiting the fluorescence properties of L1 and L2, an optical sensor array was developed featuring PVC membranes containing the dispersed sensing material and based on the Photoassisted Technique (PT) for signal acquisition, which allowed a quantitative determination of Cd2+ in real samples (soils). All phases from the design of the chemosensors to the development of the sensing device are discussed. [ABSTRACT FROM AUTHOR]

The hetero‐tetranuclear Cu2+/Ca2+/Ca2+/Cu2+ complex obtained with the N,N'‐bis((3‐hydroxy‐4‐pyron‐2‐yl)methyl)‐N,N'‐dimethylethylendiamine (Malten) ligand has been studied in solid and solution states as scaffold to bind anions. Three crystal structures showing the same metal ions sequence have been examined; they display a tetracharged complex cation neutralized by four monocharged anions. The anions play two different roles: as coordinated (two ClO4−, Cl− or NO3−) or ancillary (two ClO4−) guests. The tetranuclear scaffold hosts two anions also in aqueous and ethanol solutions. Spectrophotometric studies in ethanol allowed to determine the addition constant values for Cl− and Br− (Log K1‐2=4.43(4), 4.39(3) for Cl−, 3.80(3), 3.54(2) for Br−) while the others, although bound, showed lower affinity for the scaffold. Both the crystals and the solutions change their color depending on the added anion, namely pink, dark green or blue in the presence of ClO4−, Cl− or NO3−, respectively, thus the presence of the different anions is visible to the naked eye. The hetero‐tetranuclear Cu2+/Ca2+/Ca2+/Cu2+ complex is a versatile architecture to be used as scaffold for anion binding. [ABSTRACT FROM AUTHOR]