Application of Leuco Quinones

Leuco naphthazarins have been well studied as hair dyes.25 Human hair has been colored purplish red from dye solutions in aqueous benzyl alcohol. For example, 33 has been oxidized on hair during the drying process. 

Although leuco quinones have been studied as color formers, their use in color-forming recording media has not been studied extensively due to their instability. 

Recently, Yoshida and co-worker26 29 have developed a series of new color-forming systems using metal complexes of leuco quinones. Many bidentate ligands that produce a large bathochromic shift of absorption 

Some quinones, having the ability to form intra- and/or intermolecular hydrogen bonds, exhibit high molecular hyperpolarizability and are third-order nonlinear optical (NLO) materials. Compound 39 has a %(3) of 5 x 10 11 esu at 1.9 pm, and is a third-order NLO material.23 The optoelectric properties of quinoid compounds correlate with their structures in crystals or on thin films.23 

The Chemistry of Synthetic Dyes (K. Venkataraman, ed.), Vols. 1-7, Academic Press, New York (1952-1971). 

---

In recent years advances in the chemistry of leuco dyes have taken place particularly in the areas of structural identification by means of H- and 13C-NMR and selective syntheses of aminoquinones, etc. New applications of leuco quinones such as in electro-optical devices and information recording media have enhanced their importance. In these applications, the chemistry of leuco quinones is interesting mainly due to switching from a colored to a colorless system by a redox process. 

---