Examinando por Autor "Morales-Guevara, Rosaly"

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  • Miniatura
    Ítem
    Influence of Iodine substitutions on the photophysical properties of rhenium(I) tricarbonyl complexes with pyridine schiff base (PSB-IHB)
    (Wiley, 2025-01-08) Morales-Guevara, Rosaly; Páez-Hernández, Dayán; Ancede-Gallardo, Evys; Carreño, Alexander
    This theoretical investigation aims to evaluate the influence of iodine substitutions on the phenolic moiety of the pyridine Schiff bases harboring an intramolecular hydrogen bond (PSB-IHB) ancillary ligand within the monocationic. fac-[Re(CO)3(N,N)(PSB-IHB)]+ architecture on photophysical properties, particularly emission range. Optimized structures of two Re(I) tricarbonyl complexes (C1 and C2) were analyzed, revealing a distorted octahedral coordination geometry. Geometric parameters were compared with experimental data from analogous complexes. NBO analysis confirmed the presence of intramolecular hydrogen bonds (IHBs) in both singlet and triplet states, providing significant stabilization. Theoretical calculations predicted three distinct absorption bands for all complexes in dichloromethane, indicating substantial electronic delocalization between the pyridinic and phenolic rings via the azomethine group. These findings underscore the crucial role of delocalization and donor–acceptor interactions in stabilizing Re(I) tricarbonyl complexes and their impact on photophysical properties. Emissions calculated for the C1 and C2 complexes were observed within the range of 632–643 nm. The presence of IHBs was found to be essential for modulating photophysical properties, with emissions attributed to ligand-to-ligand charge transfer transitions.
  • Miniatura
    Ítem
    Synthesis, physicochemical characterization, and antimicrobial evaluation of halogen-substituted non-metal pyridine schiff bases
    (MDPI, 2024-10-06) Carreño, Alexander; Morales-Guevara, Rosaly; Cepeda-Plaza, Marjorie; Páez-Hernández, Dayán; Preite, Marcelo; Polanco, Rubén; Barrera, Boris; Fuentes, Ignacio; Marchant, Pedro; Fuentes, Juan A.
    Four synthetic Schiff bases (PSB1 [(E)-2-(((4-aminopyridin-3-yl)imino)methyl)-4,6-dibromophenol], PSB2 [(E)-2-(((4-aminopyridin-3-yl)imino)methyl)-4,6-diiodophenol], PSB3 [(E)-2-(((4-aminopyridin-3-yl)imino)methyl)-4-iodophenol], and PSB4 [(E)-2-(((4-aminopyridin-3-yl)imino)methyl)-4-chloro-6-iodophenol]) were fully characterized. These compounds exhibit an intramolecular hydrogen bond between the hydroxyl group of the phenolic ring and the nitrogen of the azomethine group, contributing to their stability. Their antimicrobial activity was evaluated against various Gram-negative and Gram-positive bacteria, and it was found that the synthetic pyridine Schiff bases, as well as their precursors, showed no discernible antimicrobial effect on Gram-negative bacteria, including Salmonella Typhi (and mutant derivatives), Salmonella Typhimurium, Escherichia coli, and Morganella morganii. In contrast, a more pronounced biocidal effect against Gram-positive bacteria was found, including Bacillus subtilis, Streptococcus agalactiae, Streptococcus pyogenes, Enterococcus faecalis, Staphylococcus aureus, and Staphylococcus haemolyticus. Among the tested compounds, PSB1 and PSB2 were identified as the most effective against Gram-positive bacteria, with PSB2 showing the most potent biocidal effects. Although the presence of reactive oxygen species (ROS) was noted after treatment with PSB2, the primary mode of action for PSB2 does not appear to involve ROS generation. This conclusion is supported by the observation that antioxidant treatment with vitamin C only partially mitigated bacterial inhibition, indicating an alternative biocidal mechanism.