Colorimetric and fluorescence sensing of Zn2+ ion and its bio-imaging applications based on macrocyclic "tet a" derivative

Performance of 4,5-diphenyl-1H-imidazole derived highly selective 'Turn-Off' fluorescent chemosensor for iron(III) ions detection and biological applications

Two fluorescent chemosensors, denoted as chemosensor 1 and chemosensor 2, were synthesized and subjected to comprehensive characterization using various techniques. The characterization techniques employed were Fourier-transform infrared (FTIR), proton (1 H)- and carbon-13 (13 C)-nuclear magnetic resonance (NMR) spectroscopy, electrospray ionization (ESI) mass spectrometry, and single crystal X-ray diffraction analysis. Chemosensor 1 is composed of a 1H-imidazole core with specific substituents, including a 4-(2-(4,5-c-2-yl)naphthalene-3-yloxy)butoxy)naphthalene-1-yl moiety. However, chemosensor 2 features a 1H-imidazole core with distinct substituents, such as 4-methyl-2-(4,5-diphenyl-1H-imidazole-2-yl)phenoxy)butoxy)-5-methylphenyl. Chemosensor 1 crystallizes in the monoclinic space group C2/c. Both chemosensors 1 and 2 exhibit a discernible fluorescence quenching response selectively toward iron(III) ion (Fe3+ ) at 435 and 390 nm, respectively, in dimethylformamide (DMF) solutions, distinguishing them from other tested cations. This fluorescence quenching is attributed to the established mechanism of chelation quenched fluorescence (CHQF). The binding constants for the formation of the 1 + Fe3+ and 2 + Fe3+ complexes were determined using the modified Benesi-Hildebrand equation, yielding values of approximately 2.2 × 103 and 1.3 × 104  M-1 , respectively. The calculated average fluorescence lifetimes for 1 and 1 + Fe3+ were 2.51 and 1.17 ns, respectively, while for 2 and 2 + Fe3+ , the lifetimes were 1.13 and 0.63 ns, respectively. Additionally, the applicability of chemosensors 1 and 2 in detecting Fe3+ in live cells was demonstrated, with negligible observed cell toxicity.

Intracellular Zn(II) induced turn-on fluorescence of an L-phenylalanine-derived pseudopeptide

A C2 symmetric L-phenylalanine-derived pseudopeptide has been synthesized for selective and sensitive recognition of Zn(II) ions in aqueous-organic media. The pseudopeptidic probes exhibit intracellular Zn(II) ion-sensing capabilities as demonstrated via live-cell fluorescence studies on RAW264.7 cells. Hence, we present a bioinspired pseudopeptide for potential biological applications involving intracellular Zn(II) ion detection.

A Highly Selective and Sensitive Sequential Recognition Probe Zn2+ and H2PO4- Based on Chiral Thiourea Schiff Base

A series of novel chiral thiourea fluorescent probes HL₁-HL₆ were designed and synthesized from (1R,2R)-1,2-diphenylethylenediamine, phenyl isothiocyanate, and different substituted salicylic aldehydes. All of the compounds were confirmed by ¹H NMR, ¹³C NMR, and HRMS. They exhibit high selectivity and sensitivity to Zn²⁺ in the presence of nitrate ions with the detection limit of 2.3 × 10^-8 M (HL₅). Meanwhile, their zinc (II) complexes (L-ZnNO₃) showed continuous response to H₂PO₄^- in acetonitrile solution. The identification processes could further be verified by supramolecular chemistry data analysis, X-ray single-crystal diffraction analysis, and theoretical study. The research provides reliable evidence for an explanation of the mechanism of action of thiourea involved in coordination, which is important for the application of thiourea fluorescent probes. In short, the sensors HL₁-HL₆ based on chiral thiourea Schiff base will be promising detection devices for Zn²⁺ and H₂PO₄^-.

A novel fluorescence sensor for relay recognition of zinc ions and nitric oxide through fluorescence ‘off–on–off’ functionality

The fluorescent ‘off–on–off’ probe for relay recognition of Zn²⁺ and nitro oxide (NO) was constructed with the detection limit of 10⁻⁸ mol L⁻¹.

A new 1,2,3-triazole-decorated imino-phenol: selective sensing of Zn2+, Cu2+ and picric acid under different experimental conditions

A new 1,2,3-triazole-based imino-phenol 1 is synthesized. It selectively senses Zn²⁺ in CH₃CN–H₂O with a detection limit of 1.8 × 10⁻⁶ M. Further, the selective sensing of Cu²⁺ and picric acid is achieved by the ensemble 1.Zn²⁺ in CH₃CN–H₂O.