Synthesis of (R)-tembamide and (R)-aegeline via asymmetric transfer hydrogenation in water

The synthesis of (R)-tembamide and (R)-aegeline via asymmetric transfer hydrogenation involving enantioenriched monosulfonamide–RhCp¹ complex in aqueous sodium formate as hydride donor is described.     

Computational molecular characterization of the flavonoid rutin

In this work, we make use of a model chemistry within Density Functional Theory (DFT) recently presented, which is called M05-2X, to calculate the molecular structure of the flavonoid Rutin, as well as to predict the infrared (IR) and ultraviolet (UV-Vis) spectra, the dipole moment and polarizability, the free energy of solvation in different solvents as an indication of solubility, the HOMO and LUMO orbitals, and the chemical reactivity parameters that arise from Conceptual DFT. The calculated values are compared with the available experimental data for this molecule as a means of validation of the used model chemistry.     

New heterogenized C2-symmetric bis(sulfonamide)-cyclohexane-1,2-diamine-RhCp∗ complexes and their application in the asymmetric transfer hydrogenation (ATH) of ketones in water

C₂-symmetric bis(sulfonamide) ligands derived from chiral trans-(1R,2R)-cyclohexane-1,2-diamine were immobilized on silica gel and on polystyrene resin, and complexed to Rh^IIICp∗. The resulting complexes were used as catalysts in the asymmetric transfer hydrogenation (ATH) of acetophenone. The chiral secondary alcohol was obtained in high yields (>99%) and enantioselectivities (92%) with aqueous sodium formate as the hydride source. The immobilized catalysts were recycled with no loss in activity.     

Theoretical study of electronic properties of organic photovoltaic materials

It has been proved that fullerene derivatives, in which an oligophenylenevinylene (OPV) group is attached to C(60), present an interesting photophysical phenomenon and can be incorporated into photovoltaic cells. In these systems, the OPV acts as electron donor upon excitation, and then fullerene absorbs photoexcited electrons. These new organic semiconductor materials offer the prospect of lower manufacturing costs and they present several advantages: easy fabrication, large area, flexible and light weight devices when compared with inorganic counter parts. In the present theoretical study, oligomeric chains of p-phenylenevinylene (n-PPV, n = 3-8 units) and C(60)-OPV hybrids have been studied by density functional theory (DFT). Electronic properties such as electronic absorption and emission spectra were calculated in order to determinate how the increment of spectroscopic units affects their electronic behavior. These properties were carried out with time dependent-density functional theory (TD-DFT) and ZINDO semiempirical method. The theoretical calculations of the structural properties of n-PPV and fullerene-OPV hybrids were obtained using PBE1PBE/6-31G and ONIOM two-layered version, respectively. All calculations were done with Gaussian 03W program package.     

Rheological and Morphological Properties of Carboxymethylcellulose/Starch Blends with or without ZnO and Their Applications as Inoculant Carrier

Summary: Using controlled shear-rate testing ramps, this study investigates the rheological properties of carboxymethycellulose (CMC)/starch blends, with and without zinc oxide (ZnO). Viscosity decreased as the amount of starch increased and after adding 1% ZnO. The creep and recovery tests indicated that, with increasing starch content, there was a decrease in elasticity and the viscosity zero shear rate. The results also showed, in the temperature range between 25 and 70 °C, an inversion occurred in the elastic and viscous moduli behavior, obeying the Arrhenius equation. The addition of ZnO affects the viscoelastic behavior and the morphology of the blends. The best survival results were obtained for samples 50/50 and 60/40 wt% (CMC/starch).     

2-[(R-phenyl)amine]-1,4-naphthalendiones as photosystem I electron acceptors: structure-activity relationship of m- and p-PAN compounds with QSAR analysis

Nineteen 2-[(R-phenyl)amine]-1,4-naphthalendione derivatives (PAN) were tested on spinach thylakoids for their activity as electron acceptors. These molecules act as photosystem I electron acceptors in the micromolar range. AC(50) values varied from 5 nM to 24 microM. QSAR analysis revealed a linear correlation of the m-PAN derivative log [1/AC(50)] with the energy difference of the LUMO and HOMO orbitals. The biological activity of p-PAN derivatives correlates linearly with structural parameters. Electron affinity is being the most important. The half wave I potential values (E(1/2)) of PAN compounds (from -213 to -569 mV vs. NHE) match with the mid-point potentials of the A(0) to F(X) niche of PSI electron transport carriers. The logP values of PAN derivatives were 3.35 and 3.88, indicating that they are hydrophobic compounds. Therefore PAN compounds accept electrons at the hydrophobic A(0) to F(X) niche of PSI.     

Electron-transfer reactions with significant changes in structure. Unsymmetrical crowded ethylenes

The electrochemical reduction mechanisms of xanthylideneanthrone, 6, thioxanthylideneanthrone, 7, 10-(diphenylmethylene)anthrone, 8, and 9-(diphenylmethylene)-9H-fluorene, 9, have been studied in dimethylformamide. The reduction of the first two compounds proceeds from folded forms of the neutral to twisted forms of the anion radical according to a square scheme. The data for reduction of 8 can be well accounted for by the same square scheme. However, one-step reduction with concerted electron transfer and structural change cannot be ruled out. Compound 9, whose fluorene ring system cannot fold, exists only in twisted forms in the neutral, anion radical, and dianion. Consequently, there are no major changes in structure upon reduction, and the compound is reduced in two reversible steps with the second complicated by rapid loss of the dianion that is probably due to protonation by components of the medium.     

Reduction of diesters of 1,2-diols. Regioselective C-O bond cleavage of the anionic forms

The electrochemical reduction of benzoate diesters of glycols has been studied in acetonitrile and N,N-dimethylformamide as solvents. The reductions occur in two closely spaced one-electron steps, and it was found that the dianion diradicals decompose by one of two routes, depending on the substituents on the ethylene moiety: cleavage of two benzoates to produce alkene or formation of benzil by way of a postulated cyclic intermediate to produce also the dianion of the diol. These correspond to cleavage of the R-OC(O)Ar bonds and the RO-C(O)Ar bonds, respectively. When the radical formed by the former cleavage is a primary or secondary radical, the reaction is too slow to compete with the latter reaction that produces benzil. However, when that radical is either tertiary or benzylic, the former cleavage reaction is fast and no benzil is detected. The dianions of p-cyano- and p-nitrobenzoate esters are rather stable on the voltammetric time scale. However, the addition of lithium ions results in detectable formation of 4,4'-dicyanobenzil from four different p-cyanobenzoate diesters.     

Qualitative Properties of the Solution Set for Time-Delayed Discontinuous Dynamics

This article presents a survey of several properties of the set of solutions for a differential inclusion involving a time-delayed component and with right-hand side parametrized by either an upper semicontinuous or lower semicontinuous multifunction. Our results include: existence of solutions, compactness and contractibility of the solution and reachable sets in the upper semicontinuous case, precompactness and connectedness of the solution and reachable sets in the lower semicontinuous case, regularity of the solution and reachable mappings with respect to parameters, and existence of solutions for a dynamic optimization problem.