STUDY OF PROTONATION EQUILIBRIA OF SCHIFF BASE DERIVED FROM OVANILLIN AND 1,2-DIAMINOBENZENE

Schiff bases have been extensively studied for their biological and pharmacological activities [1], as well as suitability for analytical applications. The Schiff bases derived from o-vanillin and 1,2- diaminobenzene (6-(((2-aminophenyl)imino)methyl)-2-methoxyphenol =L) presents various protonation equilibria. Their application require a detailed study of their solution chemistry. The spectroscopic and spectrofluorimetric behavior in a wide pH range in the NaCl solutions are presented. The compound exhibits a low solubility in aqueous solution and is unstable after about a week. To study the acid base properties of this system have been performed spectrophotometric and potentiometric measurements in solutions containing low concentrations of buffer systems that do not affect the acidbase behavior of the ligand. The measurements were carried out at 25 C in NaCl as ionic medium (0.1 1 M). The changes in the spectrum of solutions of the ligand in dependence of the pH were used to determine the constants of protolysis of the compoun