SOLVENT EFFECTS ON THE TAUTOMERIZATION OF 5'-DEOXYPYRIDOXAL. A PHOTOPHYSICAL STUDY |
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| Authors: | Miguel A Vázquez Segura Josefa Donoso Francisco Muñoz INÉS Fernandez de Piérola Francisco Garcia Blanco Gerardo R Echevarria |
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| Institution: | Department of Chemistry, Faculty of Sciences, University of the Balearic Islands,E–07071 Palma de Mallorca, Spain;Department of Physical Chemistry, Faculty of Sciences, UNED,E–28040 Madrid, Spain;Department of Physical Chemistry, Faculty of Pharmacy, Instituto Pluridisciplinar, Complutense University,E–28040 Madrid, Spain;Department of Physical Chemistry, University of Alcala de Henares,E–28871 Alcala de Henares, Spain |
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| Abstract: | Abstract— Absorption and fluorescence spectra of 5'-deoxypyridoxal (DPL) in various pure solvents and mixtures were recorded both at room temperature and over the range10–65°C. The areas under the absorption bands were analyzed to obtain the mole fraction (fN, fz) of two tautomers (the zwitterionic, Z, and neutral, N, forms) in the ground state. The following spectral parameters were determined from the fluorescence spectra: Stokes shift (Δ v ), fluorescence quantum yield of the neutral form (QN), fluorescence ratio of the neutral to the zwitterionic form (øN/øZ) and the rate constant of tautomerization ( k 1) from Z to N in the excited state. Some of these parameters (fN, Δ v , QN, k 1) were found to depend on the proton donor character of the solvent, whereas others (øN/øZ) depended on its dipole moment. Thus, the absorption and fluorescence spectra of DPL allow one to obtain information on the polarity and the concentration of –OH groups on its environment. |
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