Optical Anion Receptors with Urea/Thiourea Subunits on a TentaGel Support.

Two simple chemosensors with urea (L1) and thiourea (L2) groups were synthesized and studied by different spectroscopic techniques. Both receptors can sense acetate (Ac), dihydrogen phosphate (HPO ), and fluoride (F) anions, accompanied by changes in UV-vis and H NMR spectra, and an optical response is observed as a color change of the solutions due to deprotonation and hydrogen-bonding processes. Also, L1 and L2 were supported on TentaGel resins (R1 and R2), and their fluoride-sensing properties in DMSO and water solutions were studied.

Formulation of anomerization and protonation in d-glucosamine, based on H NMR.

The major anomer of non-protonated neutral d-glucosamine GlcN is the β-form, while the α-anomer is dominant for protonated cationic glucosamine GlcNH. The present work confirmed correlation between the anomerization and the protonation by simultaneous determination of signal intensity and chemical shift in pD-variation H NMR, and formulated the equilibrium constants between subspecies α-GlcN, β-GlcN, α-GlcND, and β-GlcND to interpret the correlation. The individual anomerization constants, K = [βGlcN]/[αGlcN] and K = [βGlcND]/[αGlcND], are linked to each other through the relation K∙K = K∙K with the deuteration constants K and K of the anomers.

Comparative Studies of Structures and Peroxidase-like Activities of Copper(II) and Iron(III) Complexes with an EDTA-Based Phenylene-Macrocycle and Its Acyclic Analogue.

With the objective of studying the conformational and macrocyclic effects of selected metal chelates on their peroxidase activities, Cu and Fe complexes were synthesized with a macrocyclic derivative of ethylenediaminetetraacetic acid and -phenylenediamine (abbreviated as edtaodH) and its new open-chain analogue (edtabzH). The Fe complex of edtaodH has a peroxidase-like activity, whereas the complex of edtabzH does not. The X-ray study of the former shows the formation of a dimeric molecule {[Fe(edtaod)]O} in which each metal with an octahedral coordination is overposed over the macrocyclic cavity, as a result of rigid macrocyclic frame, to form an Fe-O-Fe bridge; the exposure of the central metal to the environment facilitates the capture of oxygen to drive the biomimetic activity.

Syntheses, Characterization, and Antioxidant Evaluation of Cu, Mn, and Fe Complexes with a 14 Membered EDTA-Derived Macrocycle.

The Cu, Mn, and Fe complexes of a 14 membered macrocycle were synthesized and their antioxidant capacities were evaluated against ABTS and DPPH radicals, with the objective of collecting insights into the biomimetic role of the central metal ions. The macrocycle, abbreviated as HL14, is a derivative of EDTA cyclized with 1,4-diamine, and the moderately flexible macrocyclic frame permits the formation of [ML14·HO] chelates with octahedral coordination geometries common among the metal ions. The metal complexes were characterized by electrospray-ionization mass spectrometry, Fourier transform infrared spectroscopy, and Raman and X-ray photoelectron spectroscopic methods, as well as thermogravimetric analysis; the octahedral coordination geometries with water coordination were optimized by DFT calculations.

Silver nanoparticles synthesized with Rumex hymenosepalus extracts: effective broad-spectrum microbicidal agents and cytotoxicity study.

We synthesized silver nanoparticles using Rumex hymenosepalus root extract (Rh). Nanoparticles were subjected to a purification process and final product is a composite of Rh and silver nanoparticles (AgNPsC). Transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) were used to perform a microstructure study.

A ¹H NMR Investigation of the Interaction between Phenolic Acids Found in Mango (Manguifera indica cv Ataulfo) and Papaya (Carica papaya cv Maradol) and 1,1-diphenyl-2-picrylhydrazyl (DPPH) Free Radicals.

The benefits of phenolic acids on human health are very often ascribed to their potential to counteract free radicals to provide antioxidant protection. This potential has been attributed to their acidic chemical structure, which possesses hydroxyl groups in different positions. Phenolic acids can interact between themselves and exhibit an additive, antagonistic or synergistic effect.

Synthesis of silver nanoparticles using reducing agents obtained from natural sources (Rumex hymenosepalus extracts).

We have synthesized silver nanoparticles from silver nitrate solutions using extracts of Rumex hymenosepalus, a plant widely found in a large region in North America, as reducing agent. This plant is known to be rich in antioxidant molecules which we use as reducing agents. Silver nanoparticles grow in a single-step method, at room temperature, and with no addition of external energy.