Tartrazine: physical,thermal and biophysical properties of the most widely employed synthetic yellow food-colouring azo dye

Journal of Thermal Analysis and Calorimetry - The food-colouring dye tartrazine is a significant additive and in the same time a biologically active material. Thermal behaviour of trisodium...     

Controlling Proton and Electron Transfer Rates to Enhance the Activity of an Oxygen Reduction Electrocatalyst

An electrochemical approach is developed that allows for the control of both proton and electron transfer rates in the O₂ reduction reaction (ORR). A dinuclear Cu ORR catalyst was prepared that can be covalently attached to thiol‐based self‐assembled monolayers (SAMs) on Au electrodes using azide–alkyne click chemistry. Using this architecture, the electron transfer rate to the catalyst is modulated by changing the length of the SAM, and the proton transfer rate to the catalyst is controlled with an appended lipid membrane modified with proton carriers. By tuning the relative rates of proton and electron transfer, the current density of the lipid‐covered catalyst is enhanced without altering its core molecular structure. This electrochemical platform will help identify optimal thermodynamic and kinetic parameters for ORR catalysts and catalysts of other reactions that involve the transfer of both protons and electrons.     

Interrupted Baeyer–Villiger Rearrangement: Building A Stereoelectronic Trap for the Criegee Intermediate

The instability of hydroxy peroxyesters, the elusive Criegee intermediates of the Baeyer–Villiger rearrangement, can be alleviated by selective deactivation of the stereoelectronic effects that promote the 1,2‐alkyl shift. Stable cyclic Criegee intermediates constrained within a five‐membered ring can be prepared by mild reduction of the respective hydroperoxy peroxyesters (β‐hydroperoxy‐β‐peroxylactones) which were formed in high yields in reaction of β‐ketoesters with BF₃?Et₂O/H₂O₂.     

Bis(2,4,6-trifluorophenyl) derivatives of palladium(II)

Summary The organopalladium(II) complexes: Pd(2,4,6-C₆F₃H₂)₂L₂ [L=triphenylphosphine(PPh₃), methyldiphenylphosphine(PPh₂Me), dimethylphenylphosphine-(PPhMe₂) or pyridine(py); L₂=1,2-bis(diphenylphosphino)ethane(dpe), 2,2-bipyridine(bipy), 1, 10-phenanthroline(phen) or ethylenediamine(en)] have been prepared by addition of the appropriate compound to the THF-dioxane solution resulting from the arylation of potassium tetrachloropalladate(II) with (2,4,6-C₆F₃H₂)MgBr. The i.r. data suggest that the py and PPhMe₂ compounds are thecis-isomers, whereas the PPh₃ and PPh₂Me compounds have thetrans configuration.¹H- and¹⁹F-n.m.r. data for the compounds are reported.     

Electrocatalysis of As(III) oxidation by cobalt oxide nanoparticles: measurement and modeling the effect of nanoparticle amount on As(III) oxidation potential

Journal of Solid State Electrochemistry - The performance of electrodes modified with electrochemically generated cobalt oxide nanoparticles for the oxidation of As(III) species was investigated by...     

Formation of metal-anion arrays within layered perovskite hosts. Preparation of a series of new metastable transition-metal oxyhalides, (MCl)LaNb(2)O(7) (M = Cr,Mn, Fe,Co)

A new series of transition-metal oxyhalides (MCl)LaNb(2)O(7) (M = Cr, Mn, Fe, Co) have been prepared by a simple topochemical route. Layered perovskite hosts (ALaNb(2)O(7), A = Li, Na, K or Rb) were reacted with the corresponding anhydrous metal halides under mild reaction conditions (<400 degrees C). The compounds were examined by X-ray powder diffraction; the series appears to be isostructural with (CuCl)LaNb(2)O(7), and the layer spacings, with the exception of M = Co, follow the trend expected from transition-metal cationic radii. Thermal analysis with differential scanning calorimetry (DSC) shows the materials to be metastable where all four compounds decompose exothermically above 690 degrees C.     

Synthesis and Biological Evaluation of New N-Acyl-α-amino Ketones and 1,3-Oxazoles Derivatives

In order to develop novel bioactive substances with potent activities, some new valine-derived compounds incorporating a 4-(phenylsulfonyl)phenyl fragment, namely, acyclic precursors from N-acyl-α-amino acids and N-acyl-α-amino ketones classes, and heterocycles from the large family of 1,3-oxazole-based compounds, were synthesized. The structures of the new compounds were established using elemental analysis and spectral (UV-Vis, FT-IR, MS, NMR) data, and their purity was checked by reversed-phase HPLC. The newly synthesized compounds were evaluated for their antimicrobial and antibiofilm activities, for toxicity on D. magna, and by in silico studies regarding their potential mechanism of action and toxicity. The 2-aza-3-isopropyl-1-[4-(phenylsulfonyl)phenyl]-1,4-butanedione 4b bearing a p-tolyl group in 4-position exhibited the best antibacterial activity against the planktonic growth of both Gram-positive and Gram-negative strains, while the N-acyl-α-amino acid 2 and 1,3-oxazol-5(4H)-one 3 inhibited the Enterococcus faecium biofilms. Despite not all newly synthesized compounds showing significant biological activity, the general scaffold allows several future optimizations for obtaining better novel antimicrobial agents by the introduction of various substituents on the phenyl moiety at position 5 of the 1,3-oxazole nucleus.