Structural Diversity of Mercury(II) Halide Complexes Containing Bis-pyridyl-bis-amide with Bulky and Angular Backbones: Ligand Effect and Metal Sensing

Hg(II) halide complexes [HgCl₂] 2L¹ [L¹ = N,N’-bis(3-pyridyl)bicyclo(2,2,2,)oct-7-ene-2,3,5,6-tetracarboxylic diamide), 1, [HgBr₂(L¹)]_n, 2, [HgI₂(L¹)], 3, [Hg₂X₄(L²)₂] [X = Cl, 4, Br, 5, and I, 6; L² = N,N’-bis(4-pyridylmethyl)bicyclo(2,2,2,)oct-7-ene-2,3,5,6-tetracarboxylic diamide] and {[HgX₂(L³)]⋅H₂O}_n [X = Cl, 7, Br, 8 and I, 9; L³ = 4,4′-oxybis(N-(pyridine-3-yl)benzamide)] are reported and structurally characterized using single-crystal X-ray diffraction analyses. The linear HgCl₂ units of complex 1 are interlinked by the L¹ ligands through Hg---N and Hg---O interactions, resulting in 1D supramolecular chains. Complex 2 shows 1D zigzag chains interlinked through the Br---Br interactions to form 1D looped supramolecular chains, while the mononuclear [HgI₂L²] molecules of 3 are interlinked through Hg---O and I---I interactions, forming 2D supramolecular layers. Complexes 4–6 are isomorphous dinuclear metallocycles, and 7–9 form isomorphous 1D zigzag chains. The roles of the ligand type and the halide anion in determining the structural diversity of 1–9 is discussed and the luminescent properties of 7–9 evaluated. Complexes 7–9 manifest stability in aqueous environments. Moreover, complexes 7 and 8 show good sensing towards Fe³⁺ ions with low detection limits and good reusability up to five cycles, revealing that the Hg-X---Fe³⁺ (X = Cl and Br) interaction may have an important role in determining the quenching effect of 7 and 8.

B(C6F5)3-catalyzed three-component tandem reaction to construct novel polycyclic quinone derivatives: synthesis of a carbonate salt chromogenic chemosensor

A series novel polycyclic quinone derivatives were constructed providing a carbonate salt chromogenic chemosensor.

Chemical Waltz of Organic Molecules "On Water": Saline-Assisted Sustainable Regioselective Synthesis of Fluorogenic Heterobioconjugates via Click Reaction

A new sustainable green protocol for obtaining highly fluorogenic heterobioconjugates by a well-known copper-mediated azide-alkyne cycloaddition click reaction of nonfluorescent 3-azidocoumarins/benzyl azides (2a-f) and terminal alkynes (1a-e) using aqueous NaCl as a cheap and nontoxic salting-out agent under ultrasonication at ambient temperature is described. The presence of aqueous NaCl significantly influences the reaction by disturbing the water kosmotropes and augments the hydrophobic interaction of water-insoluble reactants, thus making the reaction feasible in water at neutral pH. The "beauty" of the presented ecofriendly approach is further boosted up by recycling the aqueous filtrate of the reaction mixture without further addition of NaCl, CuSO₄·5H₂O, and Na ascorbate up to seven cycles, resulting in effectively low copper loading (100 ppm) with excellent turn-over number (4850) and turn-over frequency (88.18 min^-1). A gram-scale synthesis was also successfully achieved with 92% yield, further elaborating the scope of this methodology.

Highly selective and sensitive ratiometric fluorescent polymer dots for detecting hypochlorite in 100% aqueous media

Hypochlorite (ClO^-), as a momentous reactive oxygen species (ROS), is highly desirable due to it associated with a number of human diseases. Therefore, the development of simple and convenient water-soluble ratiometric fluorescent probes is of great significance. In this work, water-soluble ratiometric fluorescent polymer dots (FPDs) for detecting ClO^- were prepared via incorporation of reversible addition-fragmentation chain transfer radical polymerization (RAFT), grafting technique and coprecipitation strategy. Upon the addition of ClO^-, due to the intramolecular heavy atom effect (HAE) by chlorine (Cl), the fluorescence of fluorescein units in FPDs was significantly quenched, while another reference fluorophore (P2) in FPDs keeps constant. Furthermore, the FPDs exhibited excellent sensitivity (detection limit: 2.2 nM) and selectivity, good water-solubility. In addition, FPDs was successfully utilized to detect ClO^- in tap water and drink water. It implies that the nanoprobes have the great potential applications in biological sensing and imaging.

Cation-responsive turn-on fluorescence and absence of heavy atom effects of pyridyl-substituted triarylmethyl radicals

Pyridyl-substituted triarylmethyl radicals showed cation-responsive turn-on fluorescence and did not suffer from quenching by internal and external heavy atom effects.

Ratiometric imaging of lysosomal hypochlorous acid enabled by FRET-based polymer dots

FRET-based fluorescent polymer dots (FPD) with good membrane permeability have been developed for ratiometric imaging of lysosomal HClO in living cells.

Identification of bromophenol thiohydantoin as an inhibitor of DisA, a c-di-AMP synthase, from a 1000 compound library, using the coralyne assay

c-di-AMP is an important bacterial second messenger found in Gram-positive and mycobacteria. c-di-AMP regulates myriads of processes in bacteria as well as immune response in higher organisms so interest in small molecules that would attenuate the activity of c-di-AMP metabolism enzymes is high. Herein, we report the first small molecule inhibitor of a c-di-AMP synthase, DisA, using a coralyne-based assay.

Water soluble fluorophore-carbazole–Au–DNA nanohybrid: enhanced two-photon absorption for living cell imaging application

Water soluble L–Au–DNA nanohybrid exhibits enhanced 2PA properties that can widely and evenly uptake into the lysosome of HepG2 cells.

Comparative Study of the Optical and Heat Generation Properties of IR820 and Indocyanine Green

Near-infrared (NIR) fluorophores are the focus of extensive research for combined molecular imaging and hyperthermia. In this study, we showed that the cyanine dye IR820 has optical and thermal generation properties similar to those of indocyanine green (ICG) but with improved in vitro and in vivo stability. The fluorescent emission of IR820 has a lower quantum yield than ICG but less dependence of the emission peak location on concentration. IR820 demonstrated degradation half-times approximately double those of ICG under all temperature and light conditions in aqueous solution. In hyperthermia applications, IR820 generated lower peak temperatures than ICG (4–9%) after 3-minute laser exposure. However, there was no significant difference in hyperthermia cytotoxicity, with both dyes causing significant cell growth inhibition at concentrations ≥ 5 μM. Fluorescent images of cells with 10 μM IR820 were similar to ICG images. In rats, IR820 resulted in a significantly more intense fluorescence signal and significantly higher organ dye content than for ICG 24 hours after intravenous dye administration ( p < .05). Our study shows that IR820 is a feasible agent in experimental models of imaging and hyperthermia and could be an alternative to ICG when greater stability, longer image collection times, or more predictable peak locations are desirable.