Used in hair dye formulations as a coupler to produce natural-looking brown to black shades. It reacts with primary intermediates like p-phenylenediamine in oxidative hair coloring systems to form larger colored molecules that deposit in the hair shaft. Offers good color fastness and is valued for its ability to contribute to cool, ashy tones when combined with other dye components. Also investigated for use in dye-sensitized solar cells due to its electron-donating properties, though this remains a niche application.