Propolis is a resin gathered by honey bees from trees and shrubs but it used in the beehive as building material or as an antibiotic paste. The aim of this study was to determine the content of flavonoids and phenols, as well as the antioxidant capacity of propolis from various regions of Guanajuato, Mexico. The content of flavonoids and phenols was determined by the aluminum nitrate method and the Folin-Ciocalteu method. The antioxidant capacity was determined using the free radical 2,2-diphenyl-1-picrylhydrazyl (DPPH•) method and the ferric reduction of Fe3+ to Fe2+ (FRAP•) assay. The flavonoid content varied from 13 to 379 mg of quercetin equivalents (QE) per g of propolis and the phenolic content ranged from 68 to 500 mg of caffeic acid equivalents (CAE) per g of propolis. The trolox equivalent antioxidant capacity (TEAC) per g of propolis varied from 39.8 to 54.4 for the DPPH• method and from 50 to 2000 for the FRAP• assay. Propolis rich in flavonoids and phenols possesses a low antioxidant capacity. The results show that propolis from different areas of Guanajuato are rich in flavonoids and phenolics compounds while their antioxidant capacity is variable.

Multi-ion-imprinted polymers (MIIPs) are materials with a wide range of applications mainly focused on environmental recovery, mining, technology, sensors, etc. MIIPs can incorporate ions such as heavy metals, transition metals, rare earth elements, radionuclides, and other types of ions. The chemical structures of MIIPs can be designed for different purposes and with certain morphologies, such as gels, crystals, or powders, and the surface area and porosity are also considered. All these properties provide the material with several desirable characteristics, like high selectivity, high specificity, adequate efficiency, good stability, the possibility of reusability, and strategy technology adaptation. In this review, we show the multitude of challenges of multi-ion imprinted polymer chemical synthesis based on the different and interesting methods reported previously.

Water photolysis to molecular hydrogen and oxygen is one of the most promising chemical reactions for a sustainable hydrogen generation. The search for catalysts for this process is an important research area; some of the most suggested catalysts are manganese complexes. However, several studies propose the use of the complex: tris(bipyridine)ruthenium(II) chloride to be used as catalyst in artificial photosynthesis. In spite of this, the conferred properties by the 2,2′-bipyridyl ligand, in manganese or ruthenium complexes has not yet been discussed extensively.In this work, in order to obtain more insight of the behavior of manganese(II) with several ligands such as 2,2′-bipyridyl or 1,10-phenanthroline, a spectrophotometric study of the speciation in methanol of these systems at 298K, was performed. The formation constants obtained for the manganese(II)-2, 2′-bipyridyl system are: log β110 = 7.81 and log β120 = 14.68; for the manganese(II)-1,10-phenanthroline system are log β110 = 6.94 and log β120 = 12.86. These results were obtained by refining the experimental spectrophotometric data using the HypSpec software. In addition, a brief discussion of the comparison of the calculated individual electronic spectra of the complexes reported in this work with the spectrum of the tris(bipyridine)ruthenium(II) chloride and the manganese-calcium oxygen-evolving complex of photosystem II is presented

A new Cu(II) paddle-wheel-like complex with 4-vinylbenzoate was synthesized using acetonitrile as the solvent. The complex was characterized by X-ray crystal diffraction, FT-IR, diffuse reflectance spectroscopy, thermogravimetric, differential scanning calorimetric, magnetic susceptibility, and electronic paramagnetic resonance analyses. The X-ray crystal diffraction analysis indicated that each copper ion was bound at an equatorial position to four oxygen atoms from the carboxylate groups of the 4-vinylbenzoate ligand in a square-based pyramidal geometry. The distance between the copper ions was 2.640(9) Å. The acetonitrile molecules were coordinated at the axial position to the copper ions. Exposure of the Cu(II) complex to humid air promoted the gradual replacement of the coordinated acetonitrile by water molecules, but the complex structure integrity remained. The EPR spectra exhibited signals attributed to the presence of a mixture of the monomeric (S = ½) and dimeric (S = 1) copper species in a possible 3:1 ratio. The magnetic studies revealed a peak at 50–100 K, which could be associated with the oxygen absorption capacity of the Cu(II)–vba complex.