Synthesis of Novel 3‐Aryl‐5‐dichloromethyl‐Δ2‐1,2,4‐oxadiazolines

The first synthetic approach to hitherto unknown 3‐aryl‐5‐dichloromethyl‐Δ²‐1,2,4‐oxadiazolines, of synthetic and biological interest, has been developed involving high‐yield reactions between N‐(2,2‐dichlorovinyl)benzimidoyl chlorides and hydroxylamine. The molecular structure of one member of this new family of compounds—5‐dichloromethyl‐3‐(4‐fluorophenyl)‐1,2,4‐oxadiazoline—has been determined by X‐ray crystallography. Density functional theory calculations supporting the proposed reaction pathway for the formation of these products have been carried out.     

Electronic Structure and Triplet–Triplet Energy Transfer in Artificial Photosynthetic Antennas

Three Pd(II) phthalocyanine–carotenoid dyads featuring chromophores linked by amide bonds were prepared in order to investigate the rate of triplet–triplet (T‐T) energy transfer from the tetrapyrrole to the covalently attached carotenoid as a function of the number of conjugated double bonds in the carotenoid. Carotenoids having 9, 10 and 11 conjugated double bonds were studied. Transient absorption measurements show that intersystem crossing in the Pd(II) phthalocyanine takes place in 10 ps in each case and that T‐T energy transfer occurs in 126, 81 and 132 ps in the dyads bearing 9, 10 and 11 double bond carotenoids, respectively. To identify the origin of this variation in T‐T energy transfer rates, density functional theory (DFT) was used to calculate the T‐T electronic coupling in the three dyads. According to the calculations, the primary reason for the observed T‐T energy transfer trend is larger T‐T electronic coupling between the tetrapyrrole and the 10‐double bond carotenoid. A methyl group adjacent to the amide linker that connects the Pd(II) phthalocyanine and the carotenoid in the 9 and 11‐double bond carotenoids is absent in the 10‐double bond carotenoid, and this difference alters its electronic structure to increase the coupling.     

Antibiotic protected silver nanoparticles for microbicidal cotton

Surface coating of metal nanoparticles is one of the major aspects to be optimized in the design of antimicrobial nanoparticles. The novelty of this work is that antimicrobial derivatives have been used as stabilizers to protect silver nanoparticles (Ag NPs). Microbicidal activity studies of fabricated cotton textiles coated with these Ag@Antibio were performed. Protective ligand layers of Ag NPs resulted to be a deterministic factor in their antimicrobial activity. The best bactericidal activity was obtained for Fabric TAM (coated with Ag NPs with triarylmethane derivates in surface, Ag@TAMSH), with a bacterial decrease of 3 log units for the S. aureus strain. Intrinsic antibiotic activity and partial positive charge of the TAMSH probably enhanced their antimicrobial effects. Fabric Eu (coated with Ag NPs with eugenol derivates in surface, Ag@EugenolSH) and Fabric FQPEG (coated with Ag NPs embedded in PEG-fluoroquinolone derivatives in surface, Ag@FQPEG) displayed antibacterial activity for both Staphylococcus aureus and Pseudomonas aeruginosa strains. These coated antimicrobial cotton fabrics can be applied in different medical textiles.     

A structural study of new tetrakis(1H-pyrazol-1-yl)methanes

Tetrakis(1H-pyrazol-1-yl)methanes are very rare compounds of which only two are known: the unsubstituted 1 obtained classically by Hückel in 1937 from carbon tetrachloride and prepared again several times and the 3,5-dimethyl substituted 2 obtained serendipitously by Pombeiro in 2009. We have now extended this group to include four new derivatives 8, 9, 11 and 12 bearing methyl groups. The X-ray crystal structure of the four compounds has been determined. They have been studied by NMR both in solution (¹H, ¹³C, ¹⁵N) and in the solid state (¹³C and ¹⁵N). DFT calculations of the six compounds (geometries, energies and absolute shieldings) have been used to discuss the experimental observations.     

Oxidative sulfamidation of vinyl silanes: A route to diverse silylated N-Heterocycles

The reaction of trimethyl(vinyl)silane 1 and dimethyl(divinyl)silane 2 with various sulfonamides in the oxidative system (tert-BuOCl + NaI) has been studied and shown to be an efficient approach for the synthesis of silylated N-heterocycles. Triflamide demonstrated the reactivity principally different from that of arenesulfonamides. With silane 1, it afforded the products of iodochlorination and bis(triflamidation) (major), whereas arenesulfonamides gave N-arenesulfonylaziridines in up to 91% yield. Silane 2 with arenesulfonamides yielded the products of mono and bis(iodochlorination), mono and bis(aziridination), and 3,5-diiodo-4,4-dimethyl-1-(arylsulfonyl)-1,4-azasilinanes. By contrast, triflamide, apart from the products of halogenation and iodotriflamidation, unexpectedly gave 3-(trifluoromethylsulfonyl)-5-(triflamido)oxazolidine as the main product. The structure of most heterocyclic products is proved by X-ray analysis. The effect of the silyl group in the substrate and of the substituent in the reagent on the course of oxidative sulfamidation is discussed by comparing with all-carbon analogues.     

Development of a synthetic route towards N4,N9-disubstituted 4,9-diaminoacridines: On the way to multi-stage antimalarials

A multi-step synthetic route towards N⁴,N⁹-disubstituted 4,9-diaminoacridines that, to the best of our knowledge, has no precedence in the literature, has been developed. The target structures are likely to reveal interesting biological activities in the near future, not only due to their mepacrine-like core, but also because they embed simultaneously the pharmacophores of chloroquine and primaquine, antimalarial drugs that act at different stages of malaria infection.     

First total synthesis of (±)-floribundane B: An approach based on Johnson-Claisen rearrangement of a Morita-Baylis-Hillman adduct

The first total synthesis of (±)-floribundane B is reported. Johnson-Claisen rearrangement of a Morita-Baylis-Hillman adduct assembled all of the stereochemical features of this secoiridoid. The formal synthesis of (±)-oleocanthal and the synthesis of a chemical constituent of olive press juice is also reported.     

Mechanism of the Water–Gas Shift Reaction Catalyzed by Efficient Ruthenium‐Based Catalysts: A Computational and Experimental Study

Supported ionic liquid phase (SILP) catalysis enables a highly efficient, Ru‐based, homogeneously catalyzed water‐gas shift reaction (WGSR) between 100 °C and 150 °C. The active Ru‐complexes have been found to exist in imidazolium chloride melts under operating conditions in a dynamic equilibrium, which is dominated by the [Ru(CO)₃Cl₃]^? complex. Herein we present state‐of‐the‐art theoretical calculations to elucidate the reaction mechanism in more detail. We show that the mechanism includes the intermediate formation and degradation of hydrogen chloride, which effectively reduces the high barrier for the formation of the requisite dihydrogen complex. The hypothesis that the rate‐limiting step involves water is supported by using D₂O in continuous catalytic WGSR experiments. The resulting mechanism constitutes a highly competitive alternative to earlier reported generic routes involving nucleophilic addition of hydroxide in the gas phase and in solution.     

Interfacing Formate Dehydrogenase with Metal Oxides for the Reversible Electrocatalysis and Solar‐Driven Reduction of Carbon Dioxide

The integration of enzymes with synthetic materials allows efficient electrocatalysis and production of solar fuels. Here, we couple formate dehydrogenase ( FDH ) from Desulfovibrio vulgaris Hildenborough (DvH) to metal oxides for catalytic CO₂ reduction and report an in‐depth study of the resulting enzyme–material interface. Protein film voltammetry (PFV) demonstrates the stable binding of FDH on metal‐oxide electrodes and reveals the reversible and selective reduction of CO₂ to formate. Quartz crystal microbalance (QCM) and attenuated total reflection infrared (ATR‐IR) spectroscopy confirm a high binding affinity for FDH to the TiO₂ surface. Adsorption of FDH on dye‐sensitized TiO₂ allows for visible‐light‐driven CO₂ reduction to formate in the absence of a soluble redox mediator with a turnover frequency (TOF) of 11±1 s^?1. The strong coupling of the enzyme to the semiconductor gives rise to a new benchmark in the selective photoreduction of aqueous CO₂ to formate.