Abstract
Proton transfer reactions between 4-hydroxy-2-oxo-1,2-dihydroquinolin-3-carbonitrile (HQC) and propylamine (PA), triethylamine (TEA) and piperidine (Pip) have been studied spectro-photometrically in acetonitrile as a polar solvent. The molecular compositions of the formed complexes (I, II, and III) were determined using Job's and photometric titration methods. Minimum–maximum absorbances' method has been applied to estimate the formation constants of the formed complexes (KPT). It has been found that KPT reached higher value for HQC–TEA complex than PA and Pip ones. On the basis of the rapidity of the PT-reactions, a simple and accurate spectro-photometric method for determination of HQC was proposed. Beer's law was obeyed in the concentration range 0.19 to18.60μgmL−1 with excellent correlation coefficients. The recovery percentages ranged from 99.63 to 99.99%. The solid complexes were synthesized and characterized using i.r., NMR spectroscopy and elemental analyses.
► Proton transfer complexes of HQC with different amines were investigated. ► The formation constants were estimated and evaluated. ► A spectral method was suggested for HQC determination. ► The solid complexes were synthesized and characterized.