Determination of pK_a values of azlactone dyes in non-aqueous media

摘要

4-Arylidene-2-aryl-5-oxazolone (azlactone) structures have wide range of applications arising from their promising photophysical and photochemical activities.Some of this class of dyes exhibit pH-dependent absorption and emission based response.For this reason,precise determination of the acidity constants (pK_a) of the azlactone derivatives is necessary for further studies in different media.In this study,five different azlactone derivatives were chosen to obtain pK_a values.The acidity constants were determined by using potentiometric titration method.The chosen derivatives were titrated with tetrabutylammonium hydroxide in solvents of dimethylformamide,tert-butanol,isopropanol,acetone and acetonitrile.A computerizable derivative method was used for a precise description of the end point and consequently the pK_a values.All compounds exhibited stoichiometric and well shaped potentiometric titration curves.