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UV–Visible properties of oxicams in solution: A TD-DFT and experimental study

Authors

  • Marco Franco-Pérez,

    1. Laboratorio de Fisicoquímica Analítica, Depto. de Química, Unidad de Investigación Multidisciplinaria, FES Cuautitlán, Universidad Nacional Autónoma de México, Cuautitlán Izcalli, Estado de México 54700, México
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  • Luis I. Reyes-García,

    1. Laboratorio de Fisicoquímica Analítica, Depto. de Química, Unidad de Investigación Multidisciplinaria, FES Cuautitlán, Universidad Nacional Autónoma de México, Cuautitlán Izcalli, Estado de México 54700, México
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  • Rosario Moya-Hernández,

    1. Laboratorio de Fisicoquímica Analítica, Depto. de Química, Unidad de Investigación Multidisciplinaria, FES Cuautitlán, Universidad Nacional Autónoma de México, Cuautitlán Izcalli, Estado de México 54700, México
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  • Rodolfo Gómez-Balderas

    Corresponding author
    1. Laboratorio de Fisicoquímica Analítica, Depto. de Química, Unidad de Investigación Multidisciplinaria, FES Cuautitlán, Universidad Nacional Autónoma de México, Cuautitlán Izcalli, Estado de México 54700, México
    • Laboratorio de Fisicoquímica Analítica, Unidad de Investigación Multidisciplinaria, FES Cuautitlán, Universidad Nacional Autónoma de México, Cuautitlán Izcalli, Estado de México 54700, México
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Abstract

Microspecies involved in prototropic equilibria of isoxicam, piroxicam, meloxicam, tenoxicam, and lornoxicam are characterized by time-dependent density functional theory (TD-DFT) and UV-vis spectrophotometry, their relative Gibbs free energies in solution and Maxwell–Boltzmann populations are theoretically calculated. TD-DFT calculations of the most intense transition energies for the microspecies involved in equilibria are compared with those obtained in solvents of different dielectric constants (1,4-dioxane, ethanol, water, and formamide) and at various pH conditions. Our TD-DFT results allow establishing the predominant oxicam microspecies at the experimental conditions. Geometry optimizations are performed at level of theory PCM-PBE0/6-31+G(d, p), and transition energies are computed using the protocol PCM-PBE0/6-311++G(d, p). © 2012 Wiley Periodicals, Inc.

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