Analytical Aspects of Reactions of 2-(2-Pyridyl)-benzimidazole and 2-(2-Pyridyl)-imidazoline with Iron(II)

Abstract

The compounds, 2(2-pyridyl)-benzimidazole and2(2-pyridyl)-imidazoline, of interest because of their structural similarity to 2,2',-bipyridine and o-phenanthroline, were prepared and their reactions with metal cations tested. Both were found to give color reactions with copper(I), copper(II), cobalt(II), iron(ll), and iron(III). Most notable were those with iron(II), with which deep red-purple colored complexes were formed. These complexes were studied spectrophotometrically and found to have maximum absorbances at 490 mμ for 2-(2-pyridyl)-benzimidazole at pH 5.7 and 560 mμ for 2-(2-pyridyI)-imidazoline at pH 9.0. The molar extinction coefficients for the 2-(2-pyridyl)-benzimidazoIe and 2-(2-pyridyl)-imidazoline are 3800, and 7800, respectively. Finally, the iron complexes could also be extracted with isoamyl alcohol, thus increasing the sensitivity of the color reaction.