Some New Chromogenic Reagents for Copper (I) and Iron(lI)j Pyridyl-Substituted Pyrazine and Quinoxaline Compounds

Fifteen new pyridyl-substituted pyrazine ligands have been synthesized and their IR and mass spectra are recorded. The ligands containing ethyl, methyl or phenyl groups adjacent to donor nitrogen atoms in aromatic pyridyl or pyrazine rings react only with copper(I), but the reagen ts 2,3-b is(2' -pyridyl) -5 -phenyl-5 ,6-dihydropyrazin e( III) ,2,3-bis(2' - pyridyl)-5 - P henyl-6­methyl-5,6-dihydropyrazine(V), 2,5-diphenyl-3-(2' -pyridyl)-5,6-dihydropyrazine(IX) and 2,3­bis(2' -pyridyl)-5-phenylpyrazine(XI) react with copper(I) an iron(II) to for coloured compouns. Their reactions have been studied spectrophotometrically and the effects of methyl, ethyl and phenyl groups substitution on the reactions towards copper(I) and iron(II) have been inves­tigated in terms of solution stability, molar absorptivity and wavelength of maximum absorbance.Finally the reagent bis 2,3-(6-methylpyridyl)J-5,5,6,6-tetramethyl-5,6- dihydropyrazine(II) proved to be better chromogenic reagent for copper, have been applied for the spectrophotometric determination of copper in water samples and human head hairs.

G O KHASKHELI ,M Y KHUHAWAR ,