Color reactions of PAN analogues with metal ions

Abstract

Various PAN analogues with pyridine-, nitropyridine-, or methylquinoline rings were synthesized. To study analytical properties of these compounds, their acid dissociation constants, extractability of metal chelates, and their stability constants and compositions were compared. These compounds, compared with PAN, showed greater shifts of wavelengths of maximum absorbance by chelation, and are recommendable as extractive-spectrophotometric reagents. Several of their chelates have very high molar extinction coefficients, especially those of 4'-methyl-α-QAN- and 5'-nitro-α-PAN chelates amounting to 8×10⁴.