Researches on benz- and naphthazoles XVII. Unsymmetrical formazans of the benzothiazole and benzoxazole series

1-Benzothiazolyl- and 1-benzoxazolyl-3-methyl(or phenyl)-5-arylformazans are synthesized. The depth of the color of the similarly structured 1-benzazolyl-5-arylformazans depends on the nature of the benzazole group. The power of the chromophores decreases in the following order: 1-alkyl-benzimidazole > benzothiazole > benzoxazole. Unsymmetrical 1-benzazolyl-5-arylformazans exhibit positive solvatochromism.