Víctor H. Ramos-Sánchez

Pyrene-Fullerene C60 Dyads as Light-Harvesting Antennas

A series of pyrene-fullerene C60 dyads bearing pyrene units (PyFC12, PyFPy, Py2FC12 and PyFN) were synthesized and characterized. Their optical properties were studied by absorption and fluorescence spectroscopies. Dyads were designed in this way because the pyrene moeities act as light-harvesting molecules and are able to produce “monomer” (PyFC12) or excimer emission (PyFPy, Py2FC12 and PyFN). The fluorescence spectra of the dyads exhibited a significant decrease in the amount of pyrene monomer and excimer emission, without the appearance of a new emission band due to fullerene C60. The pyrene fluorescence quenching was found to be almost quantitative, ranging between 96%–99% depending on the construct, which is an indication that energy transfer occurred from one of the excited pyrene species to the fullerene C60.

Synthesis of a Functionalized Benzofuran as a Synthon for Salvianolic Acid C Analogues as Potential LDL Antioxidants

A palladium mediated synthesis of a common synthon for the syntheses of antioxidant analogues of naturally occurring salvianolic acids is presented. The synthetic route may be used to obtain analogues with a balanced lipophilicity/hydrophilicity which may result in potentially interesting LDL antioxidants for the prevention of cardiovascular diseases.

Biopolymers from Waste Biomass — Extraction, Modification and Ulterior Uses

The residues coming from woodlands and agricultural exploitation constitute the most abundant biomass available on earth. Its importance as a source of renewable energy has grown in addition to the environmental impact. Biomass waste is a lignocellulosic feedstock which contains three main biopolymers: cellulose, hemicel‐ lulose and lignin. It could be utilized for the production of a number of value-added products due to their chemical composition, but it is necessary to efficiently recover the valuable biopolymer as intact as possible by different processing techniques.For different applications, the principal objective of pre-treatment is to keep the cellu‐ lose intact, meanwhile hemicellulose and lignin are removed. The yields of the frac‐ tions depend on the pre-treatment method, which is the most expensive step in biomass conversion. Traditionally, cellulose is obtained by kraft, sulphite and soda treatments. These methods are non-environmentally friendly and generate huge quantities of toxic wastes. Recently developed models considering the environmen‐ tal laws encourage the sustainable processing of biomass into value-added prod‐ ucts. The use of ionic liquids as new solvents for biomass waste and organosolv processes is reviewed, which are used to obtain cellulose. One of the possible appli‐ cations of cellulose is membrane synthesis, which has been reported for other bio‐ mass materials, such as sugarcane bagasse, mango seed and newspaper. In this chapter, some green pre-treatment methods, different sustainable routes for cellu‐ lose modification and some of the results obtained on membrane development based on waste biomass are discussed.

Individual and combined effect of pH and whey proteins on lactose crystallization

Lactose is recovered by crystallization from cheese whey that is a by-product of cheesemaking. The whey used for the recovery of lactose usually has a residual content of protein that alters the crystallization of lactose. In addition, the pH of whey may fluctuate depending on the cheese variety. However, there is little information on how the pH modifies the effect that whey proteins have on lactose crystallization. Accordingly, this work aimed to evaluate the individual and combined effect of whey proteins and pH on the kinetics of crystallization, the crystal size distribution and the crystallinity of lactose. The addition of whey proteins in lactose solutions (25% v/v) modified the process of lactose crystallization. However, the effect that whey proteins had on lactose crystallization heavily depended on the pH. The number of crystals per milliliter as well as the growth and size distribution of crystals was the most affected with the changes in pH (pHs of 7, 5.5 and 4) and the addition of whey proteins (0 and 0.63%). All the treatment produced mostly α-lactose monohydrated but some treatments also generated crystals of β-lactose (pH 5.5, 0% of proteins). Amorphous lactose was observed mainly in lactose solutions adjusted at pH 7 and added with whey proteins. This particular treatment also incorporated the highest amount of protein into the lattice of lactose crystals. The results of this work highlight the importance of controlling the pH of lactose crystallization, especially if there is a presence of whey proteins.

Lipase catalyzed epoxidation of fatty acid methyl esters derived from unsaturated vegetable oils in absence of carboxylic acid

Nowadays the industrial chemistry reactions rely on green technologies. Enzymes as lipases are increasing its use in diverse chemical processes. Epoxidized fatty acid methyl esters obtained from transesterification of vegetable oils have recently found applications as polymer plasticizer, agrochemical, cosmetics, pharmaceuticals and food additives. In this research article, grapeseed, avocado and olive oils naturally containing high percents of mono and poly unsaturations were used as starting materials for the production of unsaturated fatty acid methyl esters. The effect of lauric acid as an active oxygen carrier was studied on epoxidation reactions where unsaturated fatty acid methyl esters were converted to epoxy fatty acid methyl esters using immobilized Candida antarctica Lipase type B as catalyst and hydrogen peroxide as oxygen donor at mild temperature and pressure conditions. After this study it was confirmed by 1H NMR, 13C NMR and GC–MS that the addition of lauric acid to the enzymatic reaction is unnecessary to transform the alkenes in to epoxides. It was found that quantitative conversions were possible in despite of a carboxylic acid absence.

Theoretical and experimental analysis of porphyrin derivatives with suitable anchoring groups for DSSC applications

In this contribution, different porphyrin derivatives were experimentally synthesized and theoretically analyzed using several electronic structure methods to study the geometrical and electronic properties of A4, trans-A2B2and A3B porphyrins bearing several functional groups (–OH, –COOH, -3,5-di-tBu, –OCH2CH2CH2COOEt and –OMe) suitable to be employed as dyes in Dye Sensitized Solar Cells (DSSC). A4 (R = -H, -OMe, -OH, -3,5-di-tert-butyl, –OCH2CH2CH2COOEt) and A3B (R1=R2=R3=–H; R4=–OH and R4=-3,5-di-tBu) porphyrins were synthesized and characterized by UV-vis and 1H NMR spectroscopies for comparison. The geometrical parameters were analyzed in the ground state and gas phase using the semiempirical method PM6 and the DFT functionals M06-2X and B3LYP, in combination with the 6-31G(d), DZVP and TZVP basis set. For calculations of the electronic and excited state properties, CAM-B3LYP, M06-2X and HSE06, using SMD as solvation model, were applied. This study revealed that HSE06/DZVP protocol is the best method...

Sustainable Synthesis of the Naturally Hypolipidemic Agent α-Asarone

Abstract A short and practical preparation of α-asarone was developed using the inexpensive methylisoeugenol as a starting material. The utilization of a sequence of tribromination, debromination, and copper-mediated aromatic substitution enabled the stereoselective formation of only the E-isomer of α-asarone in good yield. GRAPHICAL ABSTRACT