Effect of Long-Range Corrections on Intermolecular Interactions and Vibrational Assignments of Ethylene Oxide Dimer. A Combined DFT and SQFF Study

Theoretical structural and vibrational study for the ethylene oxide dimer have been performed by using the experimental structure determined by X-ray diffraction, the vibrational spectra and, the functional hybrids B3LYP/6-311++G** and WB97XD/6-311++G** methods. Here, the effects of dispersion on intermolecular interactions and on complete assignments of infrared and Raman spectra of dimer have been performed combining the Pulay´s scaled quantum mechanical force field (SQMFF) methodology with those two levels of calculations in order to fit the theoretical wavenumbers values to the experimental ones. Calculations including long-range corrections have revealed similar optimized energy, volume and frequencies to calculated with the B3LYP/6-31G* method, lower correlations in the geometrical parameters, higher stabilization energy, higher values in the topological parameters and higher scaled force constants than the obtained at B3LYP/6-311++G** level. Natural bond order (NBO) and atoms in molecules theory (AIM) studies with both methods reveal two types of intermolecular interactions (C-O···H and C-O···O) in the ethylene oxide dimer in accordance with the bands observed in the experimental Raman spectrum at low temperatures and with the experimental structure determined at 100 K. The nature of those interactions and their topological properties were studied by using NBO and AIM calculations. The studied properties for the ethylene oxide dimer were analyzed and compared with those obtained for the monomer. Similar assignments of the vibrational modes for dimer were obtained using the three different methods

Vibrational Characterization of Active Drug to the Treatment of Chagas Disease, Benznidazole by Using Force Fields and Internal Coordinates

Two experimental structures of benznidazole active drug used to the treatment of Chagas disease have been structurally characterized and its vibrational spectra completely assigned combining B3LYP/6-311++G** calculations with the experimental FT-IR and FT-Raman spectra and the SQMFF methodology. The most stable conformer of benznidazole found in the study of the potential energy surface is in agreement with that experimentally observed by X-ray diffraction at room temperature while the other one was observed with the heating up to 195 ºC. Both differs in the positions of CH2 groups of acetamide fragment. Their structural properties in gas phase and ethanol solution were computed by using natural bond orbital (NBO), atoms in molecules (AIM), Merz-Kollman (MK) charges, molecular electrostatic potentials (MEP) and frontier orbitals calculations by using the hybrid B3LYP method and the 6-31G* and 6-311++G** basis sets. Additional WB97XD/6-311++G** calculations show that the energy values optimized for the most stable species in both media present lower values than the obtained with the B3LYP/6-31G* method. The vibrational assignments for those two conformers in both media were obtained from their corresponding harmonic force fields together with the scaled force constants

Estrategias de enseñanza en función del perfil de ingresantes a la Facultad de Bioquímica

Fil: Romano, Elida. Universidad Nacional de Tucumán. Facultad de Bioquímica, Química y Farmacia, Argentina.Fil: Raschi, Ana B. Universidad Nacional de Tucumán. Facultad de Bioquímica, Química y Farmacia, Argentina.Fil: Castillo, María V. Universidad Nacional de Tucumán. Facultad de Bioquímica, Química y Farmacia, Argentina.Fil: Brandan, Silvia A. Universidad Nacional de Tucumán. Facultad de Bioquímica, Química y Farmacia, Argentina.Fil: Yurquina, Alicia. Universidad Nacional de Tucumán. Facultad de Bioquímica, Química y Farmacia, Argentina.El conocimiento del complejo escenario donde se desarrollan los procesos educativos y los resultados cuali y cuantitativos obtenidos, han facilitado el planteo de estrategias de enseñanza para acercar soluciones al respecto. Tales propuestas han contribuido oportunamente al proceso de acreditación de las carreras llevadas a cabo en este año en nuestra facultad

Métodos espectrofotométricos para la determinación de compuestos fenólicos en propóleos

Se evaluaron tres métodos espectrofotométricos para la determinación de compuestos fenólicos totales en propóleos de la provincia de Tucumán, Argentina, mediante los métodos de Folin-Ciocalteau, azul de Prusia y o-fenantrolina. El método de azul de Prusia fue el más sensible aunque inestable; el método de o-fenantrolina fue bastante sensible y más estable que el anterior mientras que el de Folin-Ciocalteau fue el más estable y reproducible. Al comparar estadísticamente los tres métodos usados se encontró que a un nivel de significación del 1% los tres métodos son diferentes, salvo azul de Prusia y o-fenantrolina, en los que no hay diferencias significativas, utilizando el patrón quercetina.Three spectrophotometric methods were evaluated in order to determine total phenolic compounds content in propolis from Tucumán, Argentina; applying the Folin-Ciocalteau, Prussian blue and o-phenanthroline methods. The Prussian blue method was the most sensitive one although it was also unstable. The o-phenanthroline method may be more reliable and proved to be quite sensitive and stable. Folin-Ciocalteau method was the most stable and reproducible of all. The statistic analysis for such methods as well as for each of the controls used showed that all the three methods were different at 1% significance levels, except for the Prussian blue and o-phenanthroline methods, which yielded no significant differences for the quercetin control solution.Colegio de Farmacéuticos de la Provincia de Buenos Aire

Métodos espectrofotométricos para la determinación de compuestos fenólicos en propóleos

Se evaluaron tres métodos espectrofotométricos para la determinación de compuestos fenólicos totales en propóleos de la provincia de Tucumán, Argentina, mediante los métodos de Folin-Ciocalteau, azul de Prusia y o-fenantrolina. El método de azul de Prusia fue el más sensible aunque inestable; el método de o-fenantrolina fue bastante sensible y más estable que el anterior mientras que el de Folin-Ciocalteau fue el más estable y reproducible. Al comparar estadísticamente los tres métodos usados se encontró que a un nivel de significación del 1% los tres métodos son diferentes, salvo azul de Prusia y o-fenantrolina, en los que no hay diferencias significativas, utilizando el patrón quercetina.Three spectrophotometric methods were evaluated in order to determine total phenolic compounds content in propolis from Tucumán, Argentina; applying the Folin-Ciocalteau, Prussian blue and o-phenanthroline methods. The Prussian blue method was the most sensitive one although it was also unstable. The o-phenanthroline method may be more reliable and proved to be quite sensitive and stable. Folin-Ciocalteau method was the most stable and reproducible of all. The statistic analysis for such methods as well as for each of the controls used showed that all the three methods were different at 1% significance levels, except for the Prussian blue and o-phenanthroline methods, which yielded no significant differences for the quercetin control solution.Colegio de Farmacéuticos de la Provincia de Buenos Aire

Molecular structure of 4-hidroxy-3-(3-methyl-2-butenyl) acetophenone, a plant antifungal, by X-ray diffraction, DFT calculation, and NMR and FTIR spectroscopy

The molecular structure of two mixed and closely related conformers of the title compound, C13H16O2, found in the solid with unequal occupancies has been determined by X-ray diffraction methods. The substance crystallizes in the monoclinic Pca21 space group with a=17.279(2), b=5.1716(7), c=12.549(2) Å, and Z=4 molecules per unit cell. The structure was solved from 1314 reflections with I>2(I) and refined to an agreement R1-factor of 0.049. The minor conformer (34.7%) is nearly mirror-related to and extensively overlapped with the major one. The skeleton of the 4-hydroxyacetophenone molecular fragment and the prenyl group, ?(CH2)-(CH)=C(CH3)2, pendant arm attached to it are both planar and perpendicular to each other. A strong intermolecular O-H?O bond links neighboring molecules in the lattice to produce a polymeric structure. The conformational structures of the compound in the gas phase have been calculated by the DFT method and the geometrical results have been compared with the X-ray data. These data allow a complete assignment of vibration modes in the solid state FTIR and Raman spectra. The calculated 1H and 13C chemicals shifts are in good agreement with the corresponding experimental NMR spectra of the compound in solution.Fil: Piro, Oscar Enrique. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico la Plata. Instituto de Física la Plata; ArgentinaFil: Echeverria, Gustavo Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico la Plata. Instituto de Física la Plata; ArgentinaFil: Lizarraga, Emilio Fernando. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Tucumán. Instituto de Quimica del Noroeste; ArgentinaFil: Romano, Elida. Universidad Nacional de Tucuman. Facultad de Bioquimica, Quimica y Farmacia. Instituto de Quimica Inorganica; ArgentinaFil: Catalan, Cesar Atilio Nazareno. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Tucumán. Instituto de Quimica del Noroeste; ArgentinaFil: Brandán, Silvia Antonia. Universidad Nacional de Tucuman. Facultad de Bioquimica, Quimica y Farmacia. Instituto de Quimica Inorganica; Argentin

Vibrational study of caffeic acid phenethyl ester, a potential anticancer agent, by infrared, Raman, and NMR spectroscopy

The structural and vibrational properties of caffeic acid phenethyl ester (CAPE) were studied using infrared and Raman spectroscopy in the solid phase and multidimensional nuclear magnetic resonance (NMR) spectroscopy in solution. The theoretical structures of the compound and of its dimer in the gas phase and in DMSO solution by using density functional theory (DFT) were studied. The harmonic vibrational frequencies for the optimized geometry of CAPE and its dimeric species were calculated at the B3LYP level of theory using the 6–31G* basis set. These data allow a complete assignment of the vibration modes of the FTIR and Raman spectra in the solid state using the scaled quantum mechanical force field (SQMFF) methodology. The vibrational analysis for the dimer was performed taking into account the correlation diagram by means of the factor group analysis in accordance with the experimental structure determined by X-ray diffraction. The presence of the dimer of CAPE is supported by the IR bands at 1654, 1635, 1563, 1533, 1300, 1107, 1050, 738 cm−1 and the Raman bands at 1684, 1681, 1634, 1112, 1050, 928, 873, 850, 740, 445, 371 and 141 cm−1. The calculated 1H and 13C chemicals shifts are consistent with the corresponding experimental NMR spectra of the compound in solution. In addition, a natural bond orbital (NBO) study revealed the characteristics of the electronic delocalization of the stable structure, while the corresponding topological properties of the electronic charge density were analyzed by employing Bader's atoms in the molecules theory (AIM).EEA FamailláFil: Raschi, Ana Beatriz. Universidad Nacional de Tucuman. Facultad de Bioquímica, Química y Farmacia. Instituto de Química Inorganica. Cátedra de Química General; ArgentinaFil: Romano, Elida. Universidad Nacional de Tucuman. Facultad de Bioquímica, Química y Farmacia. Instituto de Química Inorganica. Cátedra de Química General; ArgentinaFil: Castillo, María Victoria. Universidad Nacional de Tucuman. Facultad de Bioquímica, Química y Farmacia. Instituto de Química Inorganica. Cátedra de Química General; ArgentinaFil: Leyton, Patricio. Pontificia Universidad Catolica de Valparaiso. Instituto de Química; ChileFil: Paipa, Carolina. Universidad de Playa Ancha. Facultad de Ciencias Naturales y Exactas. Departamento Disciplinario de Química; ChileFil: Maldonado, Luis Maria. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Famaillá; ArgentinaFil: Brandan, Silvia Antonia. Universidad Nacional de Tucuman. Facultad de Bioquímica, Química y Farmacia. Instituto de Química Inorganica. Cátedra de Química General; Argentin

Vibrational and structural study of onopordopicrin based on the FTIR spectrum and DFT calculations

In the present work, the structural and vibrational properties of the sesquiterpene lactone onopordopicrin (OP) were studied by using infrared spectroscopy and density functional theory (DFT) calculations together with the 6-31G∗ basis set. The harmonic vibrational wavenumbers for the optimized geometry were calculated at the same level of theory. The complete assignment of the observed bands in the infrared spectrum was performed by combining the DFT calculations with Pulay’s scaled quantum mechanical force field (SQMFF) methodology. The comparison between the theoretical and experimental infrared spectrum demonstrated good agreement. Then, the results were used to predict the Raman spectrum. Additionally, the structural properties of OP, such as atomic charges, bond orders, molecular electrostatic potentials, characteristics of electronic delocalization and topological properties of the electronic charge density were evaluated by natural bond orbital (NBO), atoms in molecules (AIM) and frontier orbitals studies. The calculated energy band gap and the chemical potential (μ), electronegativity (χ), global hardness (η), global softness (S) and global electrophilicity index (ω) descriptors predicted for OP low reactivity, higher stability and lower electrophilicity index as compared with the sesquiterpene lactone cnicin containing similar rings.Fil: Chain, Fernando Ezequiel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Tucumán. Instituto de Quimica del Noroeste; Argentina. Universidad Nacional de Tucumán. Facultad de Bioquímica, Química y Farmacia; ArgentinaFil: Romano, Elida. Universidad Nacional de Tucuman. Facultad de Bioquimica, Quimica y Farmacia. Instituto de Quimica Inorganica; ArgentinaFil: Leyton, Patricio. Pontificia Universidad Catolica de Valparaiso; ChileFil: Paipa, Carolina. Universidad Andres Bello; ChileFil: Catalan, Cesar Atilio Nazareno. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Tucumán. Instituto de Quimica del Noroeste; Argentina. Universidad Nacional de Tucumán. Facultad de Bioquímica, Química y Farmacia; ArgentinaFil: Fortuna, Mario. Universidad Nacional de Tucumán. Facultad de Agronomía y Zootecnia; ArgentinaFil: Brandán, Silvia Antonia. Universidad Nacional de Tucuman. Facultad de Bioquimica, Quimica y Farmacia. Instituto de Quimica Inorganica; Argentin