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Aprotic organic solvents such as acetonitrile offer a potential solution to promote electrochemical CO 2 reduction over the competing hydrogen evolution reaction. Tetraalkylammonium cations (TAA + ) are widely used as supporting electrolytes in organic media due to their high solubility and conductivity. The alkyl chain length of TAA + cations is known to influence electron transfer processes in electrochemical systems by the adsorption of TAA + , causing modifications of the double layer. In this work, we elucidate the influence of the cation chain length on the mechanism and selectivity of the CO 2 RR reaction under controlled dry and wet acetonitrile conditions on copper cathodes. We find that the hydrophobic hydration character of the cation, which can be tuned by the chain length, has an effect on product distribution, altering the reaction pathway. Under dry conditions, smaller cations (TEA + ) preferentially promote oxalate production via dimerization of the CO 2 ·- intermediate, whereas formate is favored in the presence of water via protonation reaction. Larger cations (TBA + > TPA + > TEA + ) favor the generation of CO regardless of water content. In situ FTIR analysis showed that TBA + cations are able to stabilize adsorbed CO more effectively than TEA + , explaining why larger cations generate a higher proportion of CO. Our findings also suggest that higher cation concentrations suppress hydrogen evolution, particularly with larger cations, highlighting the role of cation chain length size and hydrophobic hydration shell., Competing Interests: The authors declare no competing financial interest., (© 2024 The Authors. Published by American Chemical Society.)

Coumarins have great pharmacotherapeutic potential, presenting several biological and pharmaceutical applications, like antibiotic, fungicidal, anti-inflammatory, anticancer, anti-HIV, and healing activities, among others. These molecules are practically insoluble in water, and for biological applications, it became necessary to complex them with cyclodextrins (CDs), which influence their bioavailability in the target organism. In this work, we studied two coumarins, and it was possible to conclude that there were structural differences between 4,7-dimethyl-2 H -chromen-2-one (DMC) and 7-methoxy-4-methyl-2 H -chromen-2-one (MMC)/β-CD that were solubilized in ethanol, frozen, and lyophilized (FL) and the mechanical mixtures (MM). In addition, the inclusion complex formation improved the solubility of DMC and MMC in an aqueous medium. According to the data, the inclusion complexes were formed and are more stable at a molar ratio of 2:1 coumarin/β-CD, and hydrogen bonds along with π-π stacking interactions are responsible for the better stability, especially for (MMC) 2 @β-CD. In vivo wound healing studies in mice showed faster re-epithelialization and the best deposition of collagen with the (DMC) 2 @β-CD (FL) and (MMC) 2 @β-CD (FL) inclusion complexes, demonstrating clearly that they have potential in wound repair. Therefore, (DMC) 2 @β-CD (FL) deserves great attention because it presented excellent results, reducing the granulation tissue and mast cell density and improving collagen remodeling. Finally, the protein binding studies suggested that the anti-inflammatory activities might exert their biological function through the inhibition of MEK, providing the possibility of development of new MEK inhibitors.

The electrochemical reduction of CO 2 (CO 2 RR) is a sustainable alternative for producing fuels and chemicals, although the production of highly desired hydrocarbons is still a challenge due to the higher overpotential requirement in combination with the competitive hydrogen evolution reaction (HER). Tailoring the electrolyte composition is a possible strategy to favor the CO 2 RR over the HER. In this work we studied the solvent effect on the CO 2 RR on a nanostructured Cu electrode in acetonitrile solvent with different amounts of water. Similar to what has been observed for aqueous media, our online gas chromatography results showed that CO 2 RR in acetonitrile solvent is also structure-dependent, since nanocube-covered copper (CuNC) was the only surface (in comparison to polycrystalline Cu) capable of producing a detectable amount of ethylene (10% FE), provided there is enough water present in the electrolyte (>500 mM). In situ Fourier Transform Infrared (FTIR) spectroscopy showed that in acetonitrile solvent the presence of CO 2 strongly inhibits HER by driving away water from the interface. CO is by far the main product of CO 2 RR in acetonitrile (>85% Faradaic efficiency), but adsorbed CO is not detected. This suggests that in acetonitrile media CO adsorption is inhibited compared to aqueous media. Remarkably, the addition of water to acetonitrile has little quantitative and almost no qualitative effect on the activity and selectivity of the CO 2 RR. This indicates that water is not strongly involved in the rate-determining step of the CO 2 RR in acetonitrile. Only at the highest water concentrations and at the CuNC surface, the CO coverage becomes high enough that a small amount of C 2+ product is formed., Competing Interests: The authors declare no competing financial interest., (© 2023 The Authors. Published by American Chemical Society.)

A kinetic study of the chemiluminescent (CL) reaction mechanism of lophine-derived hydroperoxides and silylperoxides induced by a base and fluoride, respectively, provided evidence for the formation of a 1,2-dioxetane as a high-energy intermediate (HEI) of this CL transformation. This was postulated using a linear Hammett relationship, consistent with the formation of negative charge on the transition state of HEI generation (ρ > 1). The decomposition of this HEI leads to chemiexcitation with overall low singlet excited state formation quantum yield (Φ S from 1.1 to 14.5 × 10 -5 E mol -1 ); nonetheless, Φ S = 1.20 × 10 -3 E mol -1 was observed with both peroxides substituted with bromine. The use of electron-donating substituents increases chemiexcitation efficiency, while it also reduces the rate for both formation and decomposition of the HEI. Different possible pathways for HEI decomposition and chemiexcitation are discussed in light of literature data from the perspective of the substituent effect. This system could be explored in the future for analytical and labeling purposes or for biological oxidation through chemiexcitation.

Peroxiredoxins (Prx) are important proteins involved in hydroperoxide degradation and are related to virulence in several pathogens, including Aspergillus fumigatus. In this work, in vivo studies on the degradation of hydrogen peroxide (H 2 O 2 ) in the microenvironment of A. fumigatus fungus were performed by using an integrated Pt microelectrode. Three A. fumigatus strains were used to confirm the role of the cytosolic protein Prx1 in the defense mechanism of this microorganism: a wild-type strain, capable to expressing the protein Prx1; a Δprx strain, whose gene prx1 was removed; and a genetically complemented Δprx1::prx1 + strain generated from the Δprx1 and in which the gene prx1 was reintroduced. The fabricated microelectrode was shown to be a reliable inert probe tip for in situ and real-time measurements of H 2 O 2 in such microenvironments, with potential applications in investigations involving the mechanism of oxidative stress.

We modified the thiazolidinic ring at positions N3, C4, and C5, yielding compounds 6-24. Compounds with a phenyl at position N3, 15-19, 22-24, exhibited better inhibitory properties for cruzain and against the parasite than 2-iminothiazolidin-4-one 5. We were able to identify one high-efficacy trypanocidal compound, 2-minothiazolidin-4-one 18, which inhibited the activity of cruzain and the proliferation of epimastigotes and was cidal for trypomastigotes but was not toxic for splenocytes. Having located some of the structural determinants of the trypanocidal properties, we subsequently wished to determine if the exchange of the thiazolidine for a thiazole ring leaves the functional properties unaffected. We therefore tested thiazoles 26-45 and observed that they did not inhibit cruzain, but they exhibited trypanocidal effects. Parasite development was severely impaired when treated with 18, thus reinforcing the notion that this class of heterocycles can lead to useful cidal agents for Chagas disease.