Carbon Dots Prepared by Hydrothermal Treatment of Dopamine as an Effective Fluorescent Sensing Platform for the Label‐Free Detection of Iron(III) Ions and Dopamine

A facile, economic and green one‐step hydrothermal synthesis route using dopamine as source towards photoluminescent carbon nanoparticles (CNPs) is proposed. The as‐prepared CNPs have an average size about 3.8 nm. The emission spectra of the CNPs are broad, ranging from approximately 380 (purple) to approximately 525 nm (green), depending on the excitation wavelengths. Due to the favorable optical properties, the CNPs can readily enter into A549 cells and has been used for multicolor biolabeling and bioimaging. Most importantly, the as‐prepared CNPs contain distinctive catechol groups on their surfaces. Due to the special response of catechol groups to Fe³⁺ ions, we further demonstrate that such wholly new CNPs can serve as a very effective fluorescent sensing platform for label‐free sensitive and selective detection of Fe³⁺ ions and dopamine with a detection limit as low as 0.32 μM and 68 nM , respectively. The new “mix‐and‐detect” strategy is simple, green, and exhibits high sensitivity and selectivity. The present method was also applied to the determination of Fe³⁺ ions in real water samples and dopamine in human urine and serum samples successfully.     

Using “Threading Followed by Shrinking” to Synthesize Highly Stable Dialkylammonium‐Ion‐Based Rotaxanes

Herein, we report a “threading followed by shrinking” approach for the synthesis of rotaxanes by using an “oxygen‐deficient” macrocycle that contained two arylmethyl sulfone units and the dumbbell‐shaped salt bis(3,5‐dimethylbenzyl)ammonium tetrakis(3,5‐trifluoromethylphenyl)borate as the host and guest components, respectively. The extrusion of SO₂ from both of the arylmethyl sulfone units of the macrocyclic component in the corresponding [2]pseudorotaxane resulted in a [2]rotaxane that was sufficiently stable to maintain its molecular integrity in CD₃SOCD₃ at 393 K for at least 5 h.     

Heterodinuclear Lanthanoid‐Containing Polyoxometalates: Stepwise Synthesis and Single‐Molecule Magnet Behavior

Polyoxometalates (POMs) with heterodinuclear lanthanoid cores, TBA₈H₄[{Ln(μ₂‐OH)₂Ln′}(γ‐SiW₁₀O₃₆)₂] ( LnLn′ ; Ln=Gd, Dy; Ln′=Eu, Yb, Lu; TBA=tetra‐n‐butylammonium), were successfully synthesized through the stepwise incorporation of two types of lanthanoid cations into the vacant sites of lacunary [γ‐SiW₁₀O₃₆]^8? units without the use of templating cations. The incorporation of a Ln³⁺ ion into the vacant site between two [γ‐SiW₁₀O₃₆]^8? units afforded mononuclear Ln³⁺‐containing sandwich‐type POMs with vacant sites ( Ln1 ; TBA₈H₅[{Ln(H₂O)₄}(γ‐SiW₁₀O₃₆)₂]; Ln=Dy, Gd, La). The vacant sites in Ln1 were surrounded by coordinating W? O and Ln? O oxygen atoms. On the addition of one equivalent of [Ln′(acac)₃] to solutions of Dy1 or Gd1 in 1,2‐dichloroethane (DCE), heterodinuclear lanthanoid cores with bis(μ₂‐OH) bridging ligands, [Dy(μ₂‐OH)₂Ln′]⁴⁺, were selectively synthesized ( LnLn′ ; Ln=Dy, Gd; Ln′=Eu, Yb, Lu). On the other hand, La1 , which contained the largest lanthanoid cation, could not accommodate a second Ln′³⁺ ion. DyLn′ showed single‐molecule magnet behavior and their energy barriers for magnetization reversal (ΔE/k_B) could be manipulated by adjusting the coordination geometry and anisotropy of the Dy³⁺ ion by tuning the adjacent Ln′³⁺ ion in the heterodinuclear [Dy(μ₂‐OH)₂Ln′]⁴⁺ cores. The energy barriers increased in the order: DyLu (ΔE/k_B=48 K)< DyYb (53 K)< DyDy (66 K)< DyEu (73 K), with an increase in the ionic radii of Ln′³⁺; DyEu showed the highest energy barrier.     

Surfactant Hydrogels for the Dispersion of Carbon‐Nanotube‐Based Catalysts

Novel hydrogel phases based on positively charged and zwitterionic surfactants, namely, N‐[p‐(n‐dodecyloxybenzyl)]‐N,N,N‐trimethylammonium bromide (pDOTABr) and p‐dodecyloxybenzyldimethylamine oxide (pDOAO), which combine pristine carbon nanotubes (CNTs), were obtained, thus leading to stable dispersions and enhanced cross‐linked networks. The composite hydrogel featuring a well‐defined nanostructured morphology and an overall positively charged surface was shown to efficiently immobilise a polyanionic and redox‐active tetraruthenium‐substituted polyoxometalate (Ru₄POM) by complementary charge interactions. The resulting hybrid gel has been characterised by electron microscopy techniques, whereas the electrostatic‐directed assembly has been monitored by means of fluorescence spectroscopy and ζ‐potential tests. This protocol offers a straightforward supramolecular strategy for the design of novel aqueous‐based electrocatalytic soft materials, thereby improving the processability of CNTs while tuning their interfacial decoration with multiple catalytic domains. Electrochemical evidence confirms that the activity of the catalyst is preserved within the gel media.     

Conformation and Atropisomeric Properties of Indometacin Derivatives

The stereochemistry around the N‐benzoylated indole moiety of indometacin was studied by restricting the rotation about the N? C7′ and/or C7′? C1′ bond. In the 2′,6′‐disubstituted ones, an atropisomeric property was found and the atropoisomers were separated and isolated as stable forms. Their biological abilities to inhibit cyclooxygenase‐1 (COX‐1) and cyclooxygenase‐2 (COX‐2) were examined. Only the aR‐isomer showed specific inhibition of COX‐1, and COX‐2 was not inhibited by either atropisomer. Conformational analysis in NMR studies and X‐ray crystallography, and CD spectra in combination with calculations were utilized to elucidate the bioactive conformations.     

Plasmonic Scissors for Molecular Design

Heterogeneous catalysts play an important role in surface catalytic reactions, but selective bond breaking and control of reaction products in catalytic processes remain significant challenges. High‐vacuum tip‐enhanced Raman spectroscopy (HV‐TERS) is one of the best candidates to realize surface catalytic reactions. Herein, HV‐TERS was employed in a new method to control dissociation by using hot electrons, generated from plasmon decay, as plasmonic scissors. In this method, the N?N bond in 4,4′‐dimercaptoazobenzene was selectively dissociated by plasmonic scissors, and the reaction products formed from the radical fragment (SC₆H₅N) were controlled by varying the pH value. Under acidic conditions, p‐aminothiophenol was produced from the radical fragment by attachment of hydrogen ions, whereas under alkaline conditions, 4‐nitrobenzenethiol was obtained by attachment of oxygen ions to the substrate.     

Potent Antimalarial 1,2,4‐Trioxanes through Perhydrolysis of Epoxides

Perhydrolysis of a sterically congested multifunctional epoxide was achieved in ethereal H₂O₂ with the aid of a recently developed Mo catalyst. The resulting hydroperoxide cyclized to give a 1,2,4‐trioxane, which could be readily elaborated into qinghaosu and a range of novel analogues. Some of the compounds with two such trioxane moieties showed in vitro antimalarial activity comparable to or even better than that of artesunate or chloroquine.     

Coumarinylmethyl Caging Groups with Redshifted Absorption

The small and synthetically easily accessible coumarinylmethyl backbone has been modified to generate a family of photolabile protecting groups with redshifted absorption. We relied on introducing electron‐donating groups in the 7 position and electron‐withdrawing groups in the 2‐, and 2‐ and 3 positions. In particular, we showed that the diethylamino‐thiocoumarylmethyl and the diethylamino‐coumarylidenemalononitrilemethyl are relevant for uncaging with cyan light. They both exhibit a significant action cross section for uncaging in the 470–500 nm wavelength range and a low light absorption between 350 and 400 nm. These attractive features are favorable to perform chromatic orthogonal photoactivation with UV and blue‐cyan light sources, respectively.     

The Aqueous Ca2+ System,in Comparison with Zn2+, Fe3 +, and Al3 +: An Ab Initio Molecular Dynamics Study

Herein, we report on the structure and dynamics of the aqueous Ca²⁺ system studied by using ab initio molecular dynamics (AIMD) simulations. Our detailed study revealed the formation of well‐formed hydration shells with characteristics that were significantly different to those of bulk water. To facilitate a robust comparison with state‐of‐the‐art X‐ray absorption fine structure (XAFS) data, we employ a 1st principles MD‐XAFS procedure and directly compare simulated and experimental XAFS spectra. A comparison of the data for the aqueous Ca²⁺ system with those of the recently reported Zn²⁺, Fe³⁺, and Al³⁺ species showed that many of their structural characteristics correlated well with charge density on the cation. Some very important exceptions were found, which indicated a strong sensitivity of the solvent structure towards the cation′s valence electronic structure. Average dipole moments for the 2nd shell of all cations were suppressed relative to bulk water.