Browsing by Author "Paez-Hernandez, Dayan"

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    New Cationic fac-[Re(CO)3(deeb)B2]+ Complex, Where B2 Is a Benzimidazole Derivative, as a Potential New Luminescent Dye for Proteins Separated by SDS-PAGE
    (2021) Carreno, Alexander; Gacitua, Manuel; Solis-Cespedes, Eduardo; Paez-Hernandez, Dayan; Swords, Wesley B.; Meyer, Gerald J.; Preite, Marcelo D.; Chavez, Ivonne; Vega, Andres; Fuentes, Juan A.
    Sodium-dodecyl-sulfate polyacrylamide gel electrophoresis (SDS-PAGE) can be used to separate proteins based mainly on their size such as in denaturing gels. Different staining methods have been reported to observe proteins in the gel matrix, where the most used dyes are generally anionic. Anionic dyes allow for interactions with protonated amino acids, retaining the dye in the proteins. Fluorescent staining is an alternative technique considered to be sensitive, safe, and versatile. Some anionic complexes based on d(6) transition metals have been used for this purpose, where cationic dyes have been less explored in this context. In this work, we synthesized and characterized a new monocationic rhenium complex fac-[Re(CO)(3)(deeb)B2](+) (where deeb is 4,4 '-bis(ethoxycarbonyl)-2,2 '-bpy and B2 is 2,4-di-tert-butyl-6-(3H-imidazo[4,5-c]pyridine-2-yl)phenol). We carried out a structural characterization of this complex by MS+, FTIR, H-1 NMR, D2O exchange, and HHCOSY. Moreover, we carried out UV-Vis, luminescence, and cyclic voltammetry experiments to understand the effect of ligands on the complex's electronic structure. We also performed relativistic theoretical calculations using the B3LYP/TZ2P level of theory and R-TDDFT within a dielectric continuum model (COSMO) to better understand electronic transitions and optical properties. We finally assessed the potential of fac-[Re(CO)(3)(deeb)B2](+) (as well as the precursor fac-Re(CO)(3)(deeb)Br and the free ligand B2) to stain proteins separated by SDS-PAGE. We found that only fac-[Re(CO)(3)(deeb)B2](+) proved viable to be directly used as a luminescent dye for proteins, presumably due to its interaction with negatively charged residues in proteins and by weak interactions provided by B2. In addition, fac-[Re(CO)(3)(deeb)B2](+) seems to interact preferentially with proteins and not with the gel matrix despite the presence of sodium dodecyl sulfate (SDS). In future applications, these alternative cationic complexes might be used alone or in combination with more traditional anionic compounds to generate counterion dye stains to improve the process.
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    Physicochemical and Theoretical Characterization of a New Small Non-Metal Schiff Base with a Differential Antimicrobial Effect against Gram-Positive Bacteria
    (2022) Gacitua, Manuel; Carreno, Alexander; Morales-Guevara, Rosaly; Paez-Hernandez, Dayan; Martinez-Araya, Jorge I.; Araya, Eyleen; Preite, Marcelo; Otero, Carolina; Rivera-Zaldivar, Maria Macarena; Silva, Andres; Fuentes, Juan A.
    Searching for adequate and effective compounds displaying antimicrobial activities, especially against Gram-positive bacteria, is an important research area due to the high hospitalization and mortality rates of these bacterial infections in both the human and veterinary fields. In this work, we explored (E)-4-amino-3-((3,5-di-tert-butyl-2-hydroxybenzylidene)amino) benzoic acid (SB-1, harboring an intramolecular hydrogen bond) and (E)-2-((4-nitrobenzilidene)amino)aniline (SB-2), two Schiff bases derivatives. Results demonstrated that SB-1 showed an antibacterial activity determined by the minimal inhibitory concentration (MIC) against Staphylococcus aureus, Enterococcus faecalis, and Bacillus cereus (Gram-positive bacteria involved in human and animal diseases such as skin infections, pneumonia, diarrheal syndrome, and urinary tract infections, among others), which was similar to that shown by the classical antibiotic chloramphenicol. By contrast, this compound showed no effect against Gram-negative bacteria (Klebsiella pneumoniae, Escherichia coli, and Salmonella enterica). Furthermore, we provide a comprehensive physicochemical and theoretical characterization of SB-1 (as well as several analyses for SB-2), including elemental analysis, ESMS, H-1 and C-13 NMR (assigned by 1D and 2D techniques), DEPT, UV-Vis, FTIR, and cyclic voltammetry. We also performed a computational study through the DFT theory level, including geometry optimization, TD-DFT, NBO, and global and local reactivity analyses.
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    Rare-earth-based metal-organic frameworks with improved visible-light-harvesting properties: a quantum chemistry study
    (2023) Hidalgo-Rosa, Yoan; Saavedra-Torres, Mario; Koivisto, Bryan D.; Treto-Suarez, Manuel A.; Paez-Hernandez, Dayan; Zarate, Ximena; Schott, Eduardo
    This report proves that improving the visible-light-harvesting properties in rare-earth-based metal-organic frameworks (RE-MOFs) (labelled as RE-UiO-66, UiO = University of Oslo MOFs), with the aim of performing as potential visible-light-driven photocatalysts, is achievable. Thus, the design of MOFs with specific applications, especially those involving sunlight and material interactions, represents a growing field, which has been addressed in the herein work using quantum mechanical tools. We achieved to relate the light absorption properties with the structure in systems Y-UiO-66, Sc-UiO-66 and La-UiO-66, by evaluating the inclusion of well-known electron donor substituents in the structure of the 1,4-benzenedicarboxylate (BDC) linker (i.e. BDC-R, R: -CH3, -OH, -SH and -NH2). The electronic structure and optical properties of Y-UiO-66 were rigorously investigated using computational techniques combining molecular and periodic density functional theory (DFT) calculations. As a remarkable result, it was shown that including the groups -SH or -NH2 in the BDC linker, induced a shift in the absorption bands to the visible region (>= 400 nm). Hence, a group of new RE-MOFs materials with optimal structural and photocatalytic properties is proposed. This could encourage researchers to prepare these new materials to be tested in photocatalysis, such as cleaving the C-H bond, water splitting or photocatalytic degradation of organic contaminants.
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    Synthesis, Physicochemical Characterization, and Antimicrobial Evaluation of Halogen-Substituted Non-Metal Pyridine Schiff Bases
    (2024) Carreno, Alexander; Morales-Guevara, Rosaly; Cepeda-Plaza, Marjorie; Paez-Hernandez, Dayan; Preite, Marcelo; Polanco, Ruben; 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.
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    Tuning the sensitization pathway T1→5DJ in Eu-based MOF through modification of the antenna ligand. A theoretical approach via multiconfigurational quantum calculations
    (2023) Hidalgo-Rosa, Yoan; Santoyo-Flores, Julian; Treto-Suarez, Manuel A.; Schott, Eduardo; Paez-Hernandez, Dayan; Zarate, Ximena
    The current study demonstrates the possibility of improving the efficiency of Eu3+ sensitization in an Eu-based MOF, labelled as EuL-R, by modifying the antenna ligand. The electronic structure of seven antenna ligand derivatives with the form R-4-(pyrimidin-5-yl) benzoic acid (L-R) ligand derivates was thoroughly examined in this research. Also, the most likely energy transfer channels for the sensitization pathway of Eu3+ ions in the EuL-R systems (R: CH3, -OH, -SH and -NH2) was studied. The efficiency in the intersystem crossing (ISC) process from S1 to T1 in the antenna make plausible a subsequent energy transfer to the emissive state in the Eu3+. This process was studied via multireference CASSCF/NEVPT2 calculations due to the multiconfigurational character of Eu3+ ions. Based on Latva and Reindhout's empirical rules, the 4-(2-(thiophen-2-yl)pyrimidin-5-yl)benzoic acid (L6) was chosen as efficient antenna for the sensitization process in this system. In conclusion, it was discovered that including the thiophenyl group at the L antenna (L6), increased the energy gaps S1 -> T1 and T1 -> 5DJ (Eu3+) to an optimal range for the ISC and subsequent energy transfer. Finally, a deeply understanding of the sensitization and emission mechanisms was possible from the excited-state dynamics analysis of the L6 antenna, via fluorescence, inter-system crossing (ISC), phosphorescence, and kF, kISC, and kP, rates calculations. This study therefore highlights the importance of a thorough theoretical procedure via a robust quantum me-chanical tool to guide the development of novel luminescent lanthanide-based MOFs.
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    Tunning the optical properties of a photocatalytic metal-organic framework by means of molecular modelling
    (2023) Treto-Suarez, Manuel A.; Hidalgo-Rosa, Yoan; Ulecia, Karel Mena; Paez-Hernandez, Dayan; Koivisto, Bryan D.; Zarate, Ximena; Schott, Eduardo
    A theoretical study of reported isostructural metal-organic frameworks (MOFs) based on MIL-125-Ti4+ was performed to understand the optical properties and facilitate the rational design of new materials with potentially improved features as photocatalysts. The experimentally tested MOFs (MIL-125-Ti4+ labeled as M) were functionalized with -NH2, -CH3, and -OH substituents on the 1,4-benzene-dicarboxylate (BDC) linker (labeled as M-NH2, M-CH3, and M-OH, respectively), generating a broadened light-harvesting of the MOF and an improvement of the N-2 conversion rate. The M-NH2 showed the highest visible light absorption and N-2 photocatalysis efficiency experimentally. This substituent effect was theoretically studied via Density Functional Theory (DFT) calculations on the ground singlet (S-0) and first excited state (singlet and triplet) using Time-Dependent Density Functional Theory (TD-DFT), the Morokuma-Ziegler energy decomposition scheme, and Natural Orbital of Chemical Valence (NOCV) analysis. These tools allowed for the reproduction of the optical properties and performance in good agreement with the experiment and highlight that the N-2 conversion rate increases as the donor character of the R group improve. This effect is a result of the stabilization of the Occupied Molecular Orbitals (localized on the BDC linker), a decrease in the charge recombination, and by an increase of charge flow to the metal center favoring the photocatalytic Ti4+/Ti3+ reduction (via ligand to metal charge transfer (LMCT) transition). These systems also display a metal-ligand charge transfer (MLCT) process in the excited state favoring the emission localized in the BDC linker, which was confirmed via Complete Active Space Self-Consistent Field (CASSCF) calculation. Finally, through CASSCF, it was possible to propose two new isoreticular structures, with the -SH and -NO2 substituents (labeled as M-SH and M-NO2), with the -SH variant exhibiting optical and photocatalytic properties that could rival M with -NH2 substitution.