Search

This research study examined computationally the geometric, electronic, and thermodynamic properties of a group of complexes formed by aluminum(III) and some amino acids present in the ßA peptide, which are involved in the development of Alzheimer's disease. Density Functional Theory (DFT) was used for modeling complexes at the level of theory B3LYP/6-31+G(d,p) resulting in five-coordinated (CP) and four-coordinated (CT) compounds. There were aluminum(III) interactions with O and N ligands: phenolate (Ph-O-), carboxylate (COO-), carbonyl (C=O), amino (RN), and imidazole (ImN). The interactions with greater strength were phenolate and imidazole. In conclusion, the thermodynamic analyses of the structures examined showed that the five-coordinated complexes tend to be more stable than the four-coordinated complexes. [ABSTRACT FROM AUTHOR]

The structure and chemical reactivity of some derivatives of the anticancer drug cisplatin coordinated with bioactive ligands was investigated at mPW1PW/LANL2DZ level theory in the conceptual density functional theory. Global descriptors allowed analyzing the reactive nature of these complexes. The stability of the complexes increases in aqueous phase. Calculated geometries of the complexes cisplatin, carboplatín and cis-dichloro[(L,D)-Ornithine]platinum(II) are in agreement with their available X-ray data. The electrophilicity index calculated for the complexes were higher than those predicted for cisplatin, implying that the binding of these ligands favors the reactivity of these complexes [ABSTRACT FROM AUTHOR]

The reduction kinetics of allura red dye (E-129, C.I. 16035) by sodium bisulfite at level B3LYP/6-31G(d) in aqueous phase was determined. This was done to evaluate a plausible mechanistic path for the reduction reaction of this important azo dye used in the food industry. The predicted rate constants (kSulf) for the sulfonation step were in good agreement with respect to experimental rate constants reported for some dyes of chemical structure similar to Allura red. On the B3LYP potential energy surface, were located five stationary points corresponding to reactants, transition states and products. The transition states for the first and second step of the reduction reaction are presented for the first time and characterized by calculations of intrinsic reaction coordinate and vibrational frequencies. The activation thermodynamic parameters indicated than the reaction was stable, endothermic and non-spontaneous. [ABSTRACT FROM AUTHOR]

In the present work local and global descriptors of the reactivity were calculated for sunset yellow and allura red to analyze its intrinsic reactivity. The computational calculations were carried out in vacuum and aqueous phase. The aqueous phase is represented by a dielectric constant of 78.5, introduced by polarizable continuum model. The results show that allura red is less susceptible to nucleophilic addition than sunset yellow, because the electrodonor substituents methyl and methoxy decrease the capability of the azo group to accept electrons. The analysis of condensed Fukui function for a nucleophilic attack and local electrophilicity index showed that the preferred direction of attack the reducing agent (bisulfite ion) occurs on C4, which was in good agreement with experimental reports. [ABSTRACT FROM AUTHOR]