Synthesis of New Red Phthalone Pigments Derived from 2-Methylpyridinoanthrones

Abstract

A number of new red phthalone pigments were synthesized by the reaction of 2-methylpyridinoanthrones with substituted phthalic anhydrides. These were synthesized easily by the same method for the preparation of the analogous quinophthalone pigments. The red phthalone pigments have the same indigoid chromophore as that of quinophthalone pigments which are yellow in colour. It was found that the difference in colour of both pigments was attributed to the difference in the UV spectra of quinoline component.
Some pigment properties of these new phthalone pigments were studied. The lightfastness of these were very poor but it could be improved markedly by the substituent at 11-position which could take part in the intramolecular interaction such as intramolecular hydrogen bonding or chelate formation.
These new type of red phthalone pigments were suggested as the substitutes for the heavy metal inorganic pigments.