AIE and ICT Synergistic Lysosome-Targeted Ratiometric Fluorescence Sensor for the Detection and Imaging of Th4+ in the Liver of Zebrafish and Mice

The sensitive detection of the radioactive thorium (Th) ion with an oxidation state of +4 (Th4+) is of great significance for environmental protection and life safety. In this study, five fluorescence sensors with regulated donor-acceptor (D-A) interactions were constructed for Th4+ detection based on intramolecular charge transfer and aggregation-induced emission mechanisms. Among the developed sensors, TPE-D bearing electron-deficient π-bridge and weak D-A interactions presented ratiometric fluorescence detection behavior toward Th4+ in aqueous solution due to its aggregation-induced emission characteristics and unique D-A-D structures. Moreover, TPE-D showed excellent selectivity and sensitivity for Th4+ detection, and the detection limit was as low as 8.1 × 10-8 M. The sensing mechanism observation revealed that Th4+ could coordinate with the hydroxyl, imine, and carbonyl groups of TPE-D accompanied by an electron transfer process. In addition, TPE-D could selectively be enriched in the lysosome. Both the detection of Th4+ in the lysosome and liver of mice and zebrafish were realized based on this strategy, and a mobile-assisted detection approach toward Th4+ in actual water samples was also established with high sensitivity. This is the first report for Th4+ detection in organelles and organs, which provides a great significance and reliable strategy for radionuclide toxicology detection and analysis applications.

Chromene-chromene Schiff base as a fluorescent chemosensor for Th4+ and its application in bioimaging of Caenorhabditis elegans

The manuscript presents the synthesis of a new di-chromene Schiff base (COM-CH) by combining 7-(diethylamino)-2-oxo-2H-chromene-3-carbohydrazide and 4-oxo-4H-chromene-3-carbaldehyde, and its characterization using various analytical techniques. The probe COM-CH functional group contains a hard donor atom that selectively complexes with Th4+ ions. This report investigated COM-CH's sensing ability towards Th4+ chromogenic and fluorogenic methods in ACN: H2O (8:2, v/v) with Th4+ ions. The COM-CH-Th4+ complex was excited at 430 nm, resulting in a bright emission band at 475 nm with a 45 nm Stokes shift. The COM-CH probe demonstrated the highest performance at pH 4.0 to 8.0, with a sensitivity of 18.7 nM. The complex formation of COM-CH with Th4+ was investigated using NMR, FTIR spectrometry, and density functional theory calculations. The COM-CH and Th4+ are bound with 2:1 stoichiometry and an association constant of 1.92 × 108 M-2. The probe's performance enabled the analysis of monazite sand and water samples for Th4+ content. The probe successfully detected Th4+ content in Caenorhabditis elegans, marking the first Th4+ detection in animal models.

Acylhydrazones as sensitive fluorescent sensors for discriminative detection of thorium (IV) from uranyl and lanthanide ions

Thorium, as a radioactive element, is always associated with rare earth in nature. So it is an exacting challenge to recognize thorium ion (Th⁴⁺) in the presence of lanthanide ions because of their overlapping ionic radii. Here three simple acylhydrazones (AF, AH and ABr, with the functional group fluorine, hydrogen and bromine, respectively) are explored for Th⁴⁺ detection. They all exhibit excellent "turn-on" fluorescence selectivity toward Th⁴⁺ among f-block ions in aqueous medium with outstanding anti-interference abilities, where the coexistence of lanthanide and uranyl ions in addition with other ordinary metal ions have negligible effects during Th⁴⁺ detection. Interestingly, pH variation from 2 to 11 has no significant influence on the detection. Among the three sensors, AF displays the highest sensitivity to Th⁴⁺ and ABr the lowest with the emission wavelengths in the order of λ_AF-Th < λ_AH-Th < λ_ABr-Th. The detection limit of AF to Th⁴⁺ can reach 29 nM (pH = 2) with a binding constant of 6.64 × 10⁹ M^-2. Response mechanism for AF toward Th⁴⁺ is proposed based on the results of HR-MS, ¹H NMR and FT-IR spectroscopies together with DFT calculations. This work provides important implications on the development of related series of ligands in nuclide ions detection and future separation from lanthanide ions.

Copper-Catalyzed One-Pot Synthesis of 1,3-Enynes from 2-Chloro-N-(quinolin-8-yl)acetamides and Terminal Alkynes

A method for the chemo-, regio-, and stereoselective one-pot synthesis of 1,3-enynes is described. The reaction of 2-chloro-N-(quinolin-8-yl)acetamides with terminal alkynes proceeds smoothly in the presence of a copper catalyst at room temperature to produce (E)-1,3-enynes in satisfactory to excellent yields. The mechanism study reveals that the cross-dimerization of internal alkynes generated in situ with terminal alkynes proceeds via allene intermediates. The directing group 8-aminoquinoline plays a key role in the current selective synthesis of (E)-1,3-enynes.

Tetranuclear oxido-bridged thorium(iv) clusters obtained using tridentate Schiff bases

Thorium(iv) complexes are currently attracting intense attention from inorganic chemists due to the development of liquid-fluoride thorium reactors and the fact that thorium(iv) is often used as a model system for the study of the more radioactive Np(iv) and Pu(iv). Schiff-base complexes of tetravalent actinides are useful for the development of new separation strategies in nuclear fuel processing and nuclear waste management. Thorium(iv)-Schiff base complexes find applications in the colorimetric detection of this toxic metal ion and the construction of fluorescent on/off sensors for Th(iv) exploiting the ligand-based light emission of its complexes. Clusters of Th(iv) with hydroxide, oxide or peroxide bridges are also relevant to the environmental and geological chemistry of this metal ion. The reactions between Th(NO₃)₄·5H₂O and N-salicylidene-o-aminophenol (LH₂) and N-salicylidene-o-amino-4-methylphenol (L'H₂) in MeCN have provided access to complexes [Th₄O(NO₃)₂(LH)₂(L)₅] (1) and [Th₄O(NO₃)₂(L'H)₂(L')₅] (2) in moderate yields. The structures of 1·4MeCN and 2·2.4 MeCN have been determined by single-crystal X-ray crystallography. The complexes have similar molecular structures possessing the {Th₄(μ₄-O)(μ-OR')₈} core that contains the extremely rare {Th₄(μ₄-O)} unit. The four Th^IV atoms are arranged at the vertexes of a distorted tetrahedron with a central μ₄-O^2- ion bonded to each metal ion. The H atom of one of the acidic -OH groups of each 3.21 LH^- or L'H^- ligand is located on the imine nitrogen atom, thus blocking its coordination. The Th^IV centres are also held together by one 3.221 L^2- or (L')^2- group and four 2.211 L^2- or (L')^2- ligands. The metal ions adopt three different coordination numbers (8, 9, and 10) with a total of four coordination geometries (triangular dodecahedral, muffin, biaugmented trigonal prismatic, and sphenocorona). A variety of H-bonding interactions create 1D chains and 2D layers in the crystal structures of 1·4 MeCN and 2·2.4 MeCN, respectively. The structures of the complexes are compared with those of the uranyl complexes with the same or similar ligands. Solid-state and IR data are discussed in terms of the coordination mode of the organic ligands and the nitrato groups. ¹H NMR data suggest that solid-state structures are not retained in DMSO. The solid complexes emit green light at room temperature upon excitation at 400 nm, the emission being ligand-centered.