Navegando por Palavras-chave "solvatochromic properties"

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    The Methylene Blue Self-aggregation in Water/Organic Solvent Mixtures: Relationship Between Solvatochromic Properties and Singlet Oxygen Production
    (Univ Federal Mato Grosso Sul, Dept Quimica, 2017) Moreira, Leonardo Marmo; Lyon, Juliana Pereira; Lima, Adriana; Codognoto, Lucia [UNIFESP]; Severino, Divinomar; Baptista, Mauricio S.; Tessaro, Andre Luiz; Gerola, Adriana Passarela; Hioka, Noboru; Rodrigues, Maira Regina; Bonacin, Juliano Alves; dos Santos, Sandra Cruz; Romani, Ana Paula; Moises de Oliveira, Hueder Paulo
    In this work is presented a spectrophotometric investigation focused on the solvatochromic effects upon Methylene Blue (MB). Measurements were carried out in four different water/organic solvent mixtures: low polarity protic solvent (ethanol), polar non-protic solvent (acetonitrile), highly polar protic solvent (glycerol), and non-polar solvent (dioxane). The results showed that the photophysical behavior of MB is highly affected by self-aggregates formation at 80% of water/organic solvent blends. Besides polarity, the protic character and the coordinating properties of the solvent molecules are the key parameters for its photophysical behavior, since the sulfur atom of the cationic structure can act as a coordination center due to its Lewis acid character. In fact, water and acetonitrile coordinating properties have proved to be important to determine MB interactions intensity and its spectroscopic properties as singlet oxygen emission. It was observed that an increase of the amount of the organic solvent resulted in an enhancement of the singlet oxygen emission intensity. The presence of the water increases the dielectric constant of the medium and favors the self-aggregation process. Besides, the water molecules can act as a quencher and it decreases the quantum yield of the fluorescence of MB.
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    Photophysical properties of coumarin compounds in neat and binary solvent mixtures: evaluation and correlation between solvatochromism and solvent polarity parameters
    (Sociedade Brasileira de Química, 2014-05-01) Moreira, Leonardo Marmo; Melo, Mirian M. de; Martins, Priscila A.; Lyon, Juliana Pereira; Romani, Ana Paula; Codognoto, Lucia [UNIFESP]; Santos, Sandra C. dos; Oliveira, Hueder Paulo Moisés de; Universidade Federal de São João Del Rei Departamento de Zootecnia; Universidade do Vale do Paraíba Instituto de Pesquisa e Desenvolvimento; Universidade Federal de São João Del Rei Departamento de Ciências Naturais; Universidade Federal do ABC Centro de Engenharia, Modelagem e Ciências Sociais Aplicadas; Universidade Federal de São Paulo (UNIFESP); Universidade Federal de Pelotas Centro de Ciências Químicas, Farmacêuticas e de Alimentos; Universidade Federal do ABC Centro de Ciências Naturais e Humanas
    This work studied the fluorescent and solvatochromic properties of coumarin and its derivatives aiming to contribute in the elucidation of the excited state behavior of the molecule in solvent mixtures. This approach has been developed through a set of measurements involving different solvent ratios, which present distinct dielectric constants. The excitation and fluorescence maxima were largely blue-shifted with increasing participation of the organic solvent and the Stokes shifts were unusually low in mixtures with lower solvent polarity parameter, Δf. The emission intensity of coumarin was extremely sensitive to the polarity and the different structural conformations of solvents. These results influenced the spectroscopic behavior and explain the deviation from the linearity of the Lippert-Mataga relationship. The use of fluorescence spectroscopy makes the understanding of the behavior of the systems studied when in the presence of different environments being extremely important for the identification and characterization of coumarin in different pharmaceutical formulations.