Synthesis and evaluation of organic pigments.; 3. Studies based on nonmutagenic twisted benzidines

Bis-chromophoric pigments prepared using nonmutagenic benzidine analogs with high dihedral angle across the biphenyl linkage are reported. The mutagenic properties of twisted bisazomethine, disazoacetoacetanilide, disazopyrazolone, disazobenzimidazolone and disazonaphthol pigments were established using the standard Ames Salmonella mammalian mutagenicity assay and the Prival modification. Results from these tests and from the evaluation of hue, color strength and photostability of the pigments prepared are reported. Some of the new pigments are potential viable alternatives to those derived from 3,3ʹdichlorobenzidine and other genotoxic analogs of benzidine.