Visible quinacridone pigments

Similarly, 6,13-dihydroquinacridone is virtually colorless, whereas quinacridone is a colored pigment. Generally, the longer the conjugated system the longer the wavelength of the absorbed visible light. 

Plate 14 A molecule of the pigment quinacridone. The coloured surfaces represent key molecular properties predicated using computational chemistry. See Dyes and Indicators, Use of UV-Visible Absorption Spectroscopy. Reproduced with permission from Molecular Simulations (www.msi.com). 

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