Dyes of the Quarternary α-Aminopyridine Salts

Abstract

Addition of 1 mole EtI to N, N′-di-α-pyridylformamidine (I) obtained from α-amino-pyridine results in the formation of quarternary salt dye of pyridylformamidine. Further addition of 1 mole EtI results in decomposition to α-aminopyridine ethiodide (II). (I) reacts with cyclic ammonium salts containing active methylene forming quarternary salt of heterocyclic amino-ethenyl compound. Boiling (II) in anhydrous pyridine solution with ethyl orthoformate results in 1, 1′-diethyl-2, 2′-azomethinecyanine iodide, which is assumed to be a compound in which the 2 methine radicals of trimethinecyanine have been substituted by nitrogen. Spectroscepic studies of these dyes revealed that absorption maximum of pyridylaminoethenyl dyes is in a longer wave portion than the corresponding phenylaminoethenyl compounds, and that of azomethinecyanine in a shorter wave portion compared to the corresponding trimethinecyanine.