So far, several studies have focused on the synthesis of metallic nanoparticles making use of extracts from the fruit of the plants from the genus Capsicum. However, as the fruit is the edible, and highly commercial, part of the plant, in this work we focused on the leaves, a part of the plant that is considered agro-industrial waste. The biological synthesis of gold (AuNPs) and silver (AgNPs) nanoparticles using aqueous extracts of root, stem and leaf of Capsicum chinense was evaluated, obtaining the best results with the leaf extract. Gold and silver nanoparticles synthesized using leaf extract (AuNPs-leaf and AgNPs-leaf, respectively) were characterized by UV-visible spectrophotometry (UV-Vis), Fourier Transform Infrared Spectroscopy with Attenuated Total Reflection (FTIR-ATR), X-ray Photoelectron Spectroscopy (XPS), Ultra Hight Resolution Scanning Electron Microscopy coupled to Energy-Dispersive X-ray spectroscopy (UHR-SEM-EDX) and Transmission Electron Microscopy (TEM), and tested for their antioxidant and antimicrobial activities. In addition, different metabolites involved in the synthesis of nanoparticles were analyzed. We found that by the use of extracts derived from the leaf, we could generate stable and easy to synthesize AuNPs and AgNPs. The AuNPs-leaf were synthesized using microwave radiation, while the AgNPs-leaf were synthesized using UV light radiation. The antioxidant activity of the extract, determined by ABTS, showed a decrease of 44.7% and 60.7% after the synthesis of the AuNPs-leaf and AgNPs-leaf, respectively. After the AgNPs-leaf synthesis, the concentration of polyphenols, reducing sugars and amino acids decreased by 15.4%, 38.7% and 46.8% in the leaf extract, respectively, while after the AuNPs-leaf synthesis only reducing sugars decreased by 67.7%. These results suggest that these groups of molecules are implicated in the reduction/stabilization of the nanoparticles. Although the contribution of these compounds in the synthesis of the AuNPs-leaf and the AgNPs-leaf was different. Finally, the AgNPs-leaf inhibited the growth of S. aureus, E. coli, S. marcescens and E. faecalis. All of them are bacterial strains of clinical importance due to their fast antibiotic resistance development.

An N,P-heterocyclic germylene/B(C F ) Lewis adduct 2 presenting multi-reactive sites (P/B Lewis pair, germylene, Ge=P π-bond) is reported. In contrast to classical frustrated Lewis pairs or divalent Group 14 element species, 2 is able to activate two small molecules simultaneously. Of particular interest, 2 reacts with silanes leading to the formation of original cationic germylenes 3, and can be used as a metal-free catalyst for selective CO -hydrosilylation to H C(OSiEt ) .

Ad iastereo-and regioselective methodf or accessing av ariety of highly functionalized Z-enol-g-lactones in good yields through the cycloisomerization of b-hydroxy-galkynoic acids catalyzed by CuBr (5 mol %) in water under microwaveh eating in as hort time is described.

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An N,P‐heterocyclic germylene/B(C6F5)3 Lewis adduct 2 presenting multi‐reactive sites (P/B Lewis pair, germylene, Ge=P π‐bond) is reported. In contrast to classical frustrated Lewis pairs or divalent Group 14 element species, 2 is able to activate two small molecules simultaneously. Of particular interest, 2 reacts with silanes leading to the formation of original cationic germylenes 3, and can be used as a metal‐free catalyst for selective CO2‐hydrosilylation to H2C(OSiEt3)2.

No abstract

LOPEZ-REYES*, M. E.; TOSCANO, R. A.; LOPEZ-CORTES, J. G.; ALVAREZ-TOLEDANO, C.; Asian J. Org. Chem. 4 (2015) 6, 545-551, http://dx.doi.org/10.1002/ajoc.201500013 ; Inst. Quim., Univ. Nac. Auton. Mex., Coyoacan, 04510 Mexico, Mex.; Eng.) -F. Berndt 51-106

La química de coordinación es un tema que resulta muy interesante para los estudiantes, debido en parte a que el razonamiento sobre el desdoblamiento de los orbitales-d puede ser confirmado con las propiedades espectroscópicas de los compuestos, particularmente sus colores. Sin embargo, en los cursos introductorios de química inorgánica es difícil para los estudiantes determinar si un complejo de coordinación homoléptico tipo Werner, tiene una configuración de alto o bajo espín. En esta contribución, proponemos dos diagramas que guían a los estudiantes para encontrar esta respuesta.